Marine & Offshore Technology

Marine & Offshore Technology

S C H I P m W E R F

56STE JAARGANG NR 7 JULI 1989

Dynamic Positioning Harbour Tug Design

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M arine & Offshore Technology 'Schip en W erf is het officiële orgaan van de Nederlandse Vereniging van Technici op Scheepvaartgebied, Het Maritiem Research Instituut Nederland MARIN, De Vereniging Nederlandse Scheepsbouw Industrie VNSI en de Afdeling Maritieme Techniek van het Klvl..

Verschijnt maandelijks

RedactieP. A. Luikenaar, Dr. ir. P. van Oossanen,Dr. ir. K. J. Saurwalt, Ing. C. Dam en J. M. Veltman

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Inhoud

Nederlandse zeescheepvaart op weg naar herstel 223

Dynamic Positioning 225

Navtex 235

Noise levels and noise control 237

Notes on harbour tug design 242

Literature 247

Nieuwsberichten 249

Verenigingsnieuws 253

In dit nummer vindt u een bijlage van TU- Delft/WEGEMT.

Marine & Offshore Technology

SCHIP EN WERFNEDERLANDSE ZEESCHEEPVAART OP WEG NAAR HERSTEL’De weg naar herstel is ingeslagen’. D it is wel de belangrijkste boodschap die het jaarverslag 1988 van de Koninklijke Nederlandse Redersvereniging (KNRV) brengt. De oorzaak daarvan was vooral een stijging van de groei van de wereldhandel en daarnaast de vermindering van het aanbod van scheepsruimte in de afgelopen jaren, doordat veel van de overcapaciteit aan tonnage gesloopt werd. Overigens was vorig jaar het herstel nog slechts beperkt to t enkele sectoren. Op wat langere termijn w ordt echter een meer algemene verbetering van de zeevrachtenmarkt verwacht. Er gloort dus weer nieuwe hoop voor de toekomst, waarin ook de scheepsbouw kan delen. Immers, een gezonde en renderende zeescheepvaart betekent méér werk voor de scheepswerven met betrekking to t nieuwbouw en reparatie. Voorzichtigheidshalve wijst de KNRV er echter op, dat het nog wel geruime tijd zal duren, voordat de rendementen op een zodanig niveau zijn aangeland, dat de in het verleden opgetreden uitholling van vermogen w ordt gecompenseerd en plaats maakt voor rendementen, die de continuïte it op lange termijn veilig zullen stellen.In verschillende landen werden in de afgelopen jaren maatregelen getroffen om de reders te helpen, ook in Nederland. In de ons omringende landen verlopen de veranderingen echter zó snel dat Nederland, ondanks een voortvarende start, achterop dreigt te raken. Men zal zich wellicht herinneren, dat met de Nota 'Wél varen onder Nederlandse vlag’, die in 1986 werd uitgebracht door de minister van Verkeer en Waterstaat, later aangevuld door de moties van de Tweede Kamer, een beleid to t behoud van de Nederlandse zeescheepvaart werd uitgestippeld. Gekozen werd daarbij voor een verbetering van de concurrentiepositie van deze bedrijfstak, via een aanpassing van de bestaande Nederlandse wetgeving. Doel van de overheid daarmee was te bereiken, dat de gekwalificeerde werkgelegenheid en de

hoogwaardige kennis voor de maritieme sector in Nederland behouden zou blijven. Voorwaarde is echter, aldus het jaarverslag, dat het pakket maatregelen to t behoud van de nationale zeescheepvaart thans op korte termijn en ook in zijn geheel w ordt gerealiseerd.Nu de weg naar herstel is ingeslagen zegt de KNRV erop te vertrouwen zich op deze weg in goed gezelschap te bevinden van de overheid en haar sociale partners, omdat het alleen gezamenlijk mogelijk is te komen to t een meer en ook blijvend herstel van de scheepvaart onder de Nederlandse vlag.Reeds in 1987 was een verbetering van de situatie op de internationale zeevrachtenmarkt bemerkbaar. Deze heeft zich in 1988 voortgezet. Er is een evenwicht bereikt tussen vraag en aanbod van scheepsruimte. Deze verbetering van de markt w ordt vooral veroorzaakt door een groei van de vraag naar vervoersdiensten, die een gevolg is van de onverwachte sterke economische opleving en groei van de wereldhandel. Het aanbod van tonnage is sinds het begin van de jaren tachtig verminderd door een versnelde sloop van scheepsruimte en een vermindering van de omvang van de nieuwbouw. Deze vertoonde dan ook in 1988 een historisch dieptepunt. De aantrekkende conjuctuur is er de oorzaak van dat de sloop vafrton- nage verminderde.Het is in het bijzonder de droge bulkvaart die in 1988 geprofiteerd heeft van de gunstiger gang van zaken op de zeevrachtenmarkt. In de tankvaart kon echter, en vooral in de tweede helft van het jaar, een verbetering van de resultaten worden geconstateerd. Jammer genoeg echter is de lijnvaart bij deze positieve ontwikkeling achter gebleven, ook al groeide op een aantal routes het ladingvolume. D it resulteerde echter slechts op enkele gecontai- neriseerde trajecten to t vrachtprijsverhogingen van enige betekenis. De vrachtprijs ontwikkeling in de koel- en vriesvaart was

SenW 56STE jAARGANG NR 7 223

eveneens positief en in deze sector heerst daarin dan ook optimisme met het oog op de toekomst. Niettemin is hier wat onzekerheid ontstaan door het toenemen van het nieuwbouworders op koel- en vriesschepen, als gevolg waarvan weer een overcapaciteit in de toekomst zou kunnen ontstaan met alle gevolgen van dien. Het is nog altijd zo, dat een vleugje opleving nieuwbouworders to t gevolg heeft. Men realiseert zich dan kennelijk niet voldoende meer dat de trieste gang van zaken in de zeescheepvaart in de jaren tachtig voor een belangrijk deel het gevolg was van de overcapaciteit aan scheepsruimte, die thans grotendeels opgeruimd is.De opleving in de offshore dienstverlening, waaronder de zeesleepvaart, de bevoorra- dingsvaart en de booractiviteiten, vertoond in het afgelopen jaar een aarzelende tred, aldus het verslag. Wel nam de bezettingsgraad van het materieel toe, maar de tarieven bleven aan de lage kant. Over vrijwel de gehele linie moet worden geconstateerd, dat de huidige vrachttarieven nog te laag zijn om voor nieuwe investeringen, bij de gestegen bouwprijzen, de exploitatie- en kapitaalkosten op te brengen. De KNRV wijst erop, dat in afwachting van het door de overheid aangekondigde pakket van maatregelen to t behoud van de zeescheepvaart onder Nederlandse vlag, de sterke inkrimping van de Nederlandse handelsvloot voorlopig gestopt is. In de grote vaart bleef de tonnage nagenoeg gelijk, In de kleine handelsvaart had een relatief geringe uitvlagging plaats. In het algemeen kan hier nog bij worden opgemerkt, dat onder invloed van de verbeterde marktperspectieven de investeringsbe- reidheid in 1988 weer toenam.Hoe staan de reders tegenover Europa 1992? Het KNRV-verslag zegt dat 1988 het jaar was waarin de Euro-euforie hoogtij vierde. Geen onderneming of brancheorganisatie kan nog om een beleid gericht op 'Europa 1992’ heen. Analyses tonen echter aan dat de effecten weliswaar positie f zijn, maar waarschijnlijk beperkter dan aanvankelijk verondersteld werd. N iettemin blijft ook voor reders zaak de ontw ikkelingen nauwkeurig te volgen en actief in te spelen op kansen èn bedreigingen. De visies van reders en overheid t.a.v. de Europese scheepvaartpolitiek lopen nagenoeg parallel. De Nederlandse reders staan positief tegenover een versterking van deze politiek en tegenover de bijdrage die de Nederlandse overheid hieraan levert.W at de kleine handelsvaart betreft heeft voorzitter drs. L. E. Straus van de Vereniging van Nederlandse Reders in de Kleine Handelsvaart (VNRK) in zijn jaarrede aan de leden voorgerekend, wat het de gezamenlijke Nederlandse reders kost om onder Nederlandse vlag te blijven varen. Hij ging er daarbij vanuit, dat er zo’n 10.000 werknemers onder Nederlandse vlag va

ren, en dat de gagekosten van een Nederlands bemanningslid gemiddeld genomen zo’n 60.000 gulden per jaar hoger liggen dan die van Oost-Aziaten. Dan bedragen de meerkosten van de Nederlandse reders, in vergelijking met schepen die geheel met Oost-Aziaten bemand zijn, gezamenlijk 10.000 x 60.000 gulden, dat wil zeggen 600 miljoen gulden.De vraag duikt op of daar besparingen te genover staan. Dat is volgens drs. Straus niet het geval. Havenkosten, bunkerkos- ten en verzekeringspremies zijn internationaal voor iedereen gelijk. De onderhoudskosten hangen enerzijds af van in ternationaal bepaalde prijzen van grondstoffen en anderzijds van de resp. loonkostenniveaus van de landen waarin het onderhoud plaats vindt. Doordat er enige vrijheid voor mondiaal varende schepen is in de keuze van het land, kunnen deze kosten toch wel enigszins genivelleerd worden. De Nederlandse reders in de kleine handelsvaart, w ier werkterrein veel dichter bij huis ligt, hebben deze keuze in een veel geringere mate. Die zijn dus in hoofdzaak aangewezen op de Nederlandse, althans Europese werven, met hun relatief hogere loonkosten - zij het dat d it soms, maar zeker niet altijd - w ordt gecompenseerd door grotere produktiviteit en dus minder tijdverlies.Het is ondoenlijk de rede van de voorzitte r hier uitvoerig te bespreken en te citeren. In het algemeen ook gaat het om zaken die bekend zijn. Hij noemde onder meer een tweetal factoren van groot belang die de aandacht vragen, die modern zijn en volop in de belangstelling staan: milieu en energiebesparing. Er bestaat geen transportmiddel, aldus de voorzitter, dat minder bijdraagt aan de belasting dan de scheepvaart. Er bestaat evenmin een transportmiddel dat per ton mijl zo zuinig is in energiegebruik als de scheepvaart. O ndanks alle olieverlies, vervuiling door gevaarlijke stoffen bij aanvaringen en dergelijke, heeft het Duitse ministerie van Economische Zaken vastgesteld, dat de vervuiling van de Noordzee voor slechts 5 pet kan worden toegeschreven aan de scheepvaart. De trein, een goede tweede, verbruikt elektrische stroom die opgewekt wordt door milieuvervuilende fossiele brandstoffen o f door kerncentrales. Maar een trein vereist ook een spoorwegnet, dat het landschap op alle mogelijke manieren doorsnijdt en doorsnijdt, en rangeerterreinen en bovenleidingen.Van al dat staal en koper, om van de wagons nog niet te spreken, kunnen heel wat schepen worden gebouwd. Spreker gaf de volgende vergelijking: één schip met 2000 containers kun je overladen op 1000 spoorwegwagons met een gezamenlijke lengte van zo’n 15 km. Een schip vaart op het water en water is overal. En dan de energiebesparing! Datzelfde schip vaart in 24 uur naar Hamburg en heeft zo’n 20.000

pk motorvermogen met een verbruik van 75 ton per dag. Voor datzelfde stuk werk heb je 2000 vrachtauto’s nodig, die het weliswaar in minder dan de helft van de tijd zouden doen, maar daarvoor heeft iedere vrachtauto ongeveer 300 pk nodig. Dat is in totaal 600.000 pk met een verbruik van op z’n best I op 2,5. Dat is dus op een afstand van 550 km vanaf de Maasvlakte 220 liter per vrachtauto, o f 375.000 ton met z’n allen. Dat is vijf keer zoveel als de scheepvaart, en dan laten we het milieuaspect en vervuiling van wegen nog maar buiten beschouwing. Het is echter een duidelijke zaak dat elke vooruitziende overheid met verantwoordelijkheidsgevoel niet om de scheepvaart heen kan. En dat wil de Nederlandse overheid ook niet. Maar wat is er nu terechtgekomen van het door haar in 1987 uitgestippelde vierspo- renbeleid: bemanningsschaalreductie, varen met goedkope buitenlanders, fiscale faciliteiten voor zeevarenden die ten goede moesten komen aan de reders, en subsidie voor investering in schepen.Aan het eerste punt is voldaan. W at het tweede spoor aangaat: in de kleine handelsvaart belemmert het ene ministerie het soelaas dat het andere wil bieden. Geen ideale toestand dus. Het derde spoor: de fiscale faciliteit is nog steeds niet aan de Staten Generaal aangeboden en dus nog niet ingevoerd. En het vierde spoor: de Investeringspremieregeling Zeescheepvaart betreft: ultimo 1989 loopt deze af zonder dat op dit moment bekend is of zij nadien opnieuw zal worden ingevoerd of dan wel vervangen. Een onzekere situatie dus. De conclusie is dat de reders zelf nog steeds de overgrote last van het wèlvaren onder Nederlandse vlag blijven dragen.Hoe dit alles ook zij, de VNRK zal aan de ftscus duidelijk trachten te maken dat 80 pet van de verdiensten van het rederijbe- d rijf buiten Nederland w ordt verdiend en daarom belast moet worden met een speciaal buitentarief. D it laatste vooral zou de Nederlandse reders die weer winst zouden maken, in staat stellen om weer wat vermogen terug te vormen dat in de afgelopen jaren verloren is gegaan, en ook in d it opzicht de concurrentie voor Nederland met goedkope vlaglanden mogelijk maken. O ok zal getracht worden de investeringsaftrek en vervroegde afschrijving weer ingevoerd te krijgen, alsmede een vorm van investeringsaftrek te handhaven. De voorzitter meent dat, als dit geheel of gedeeltelijk succes oplevert, het varen onder Nederlandse vlag aantrekkelijk zal blijven: ’En dan zullen w ij onder Nederlandse vlag blijven varen'. Hij houdt echter een slag om de arm: 'Als tenminste de overheid en de vakbonden ons dat niet alsnog onmogelijk zullen maken’.

vHk

224 SenW 56STE jAARGANG NR 7

DYNAMIC POSI*by A. Lough**

SYNO PSISThis paper deals with the development o f dynamic positioning systems and their application in connection with the offshore and allied industries. Details are given o f the principles of operation together with the relevant features necessary to obtain dynamic positioning control of a vessel with a detailed account o f the more commonly used position reference systems. The second part o f the paper deals with the classification aspects, survey procedures and development of the Society's Rules for dynamic positioning systems.

I. IN T R O D U C T IO NDynamic positioning is a relatively recent innovation in maritime terms, having developed over the last tw o decades as a result o f the transition from shallow water to deep water oil and gas exploration where, in many cases, it is impractical to use conventional mooring systems.The first ship to be assigned one o f the Society’s DP classification notations was the ’Nand Shamik’ (ex Shearwater Sapphire), which was built in 1982 to DP (AA) requirements.

Com m anded position /head ing

Position heading Thrustercon tro l a lgon thm alloca tion log ic

Reference ‘ W indpo s ition heading com pensation

Fig. I Dynamic Positioning - Basic Concept

A dynamnic positioning (DP) system is defined, for the purposes of this paper, as a computer assisted manoeuvring system, including all the equipment necessary to provide means of controlling the position and heading of a vessel or mobile offshore unit within pre-defined limits, exclusively by active thrust. See Figure I .It is not the intention o f a dynamic positioning system to keep the vessel at any

* This paper was presented to members of Lloyd’s Register Technical Association on the 2nd October, 1985.

* Senior Surveyor Control Engineering Department Engineering Services/Croydon Lloyd’s Register of Shipping.

one fixed point above the sea bed, but within an area of operation which is determined by the operational mode of the vessel.A dynamic positioning system controls only three of the six modes of motion, i.e. surge, sway and yaw, by controlling the pitch or rpm o f the thruster units against the wind, sea current and wave forces to keep the vessel in its operational area. See Figure 2.The DP system does not control the effects of heave, pitch and roll o r lateral vessel motions due to first order wave effects. Dynamic positioning was also developed to cater for situations where the deployment o f anchors to maintain the vessel on station could cause a hazard to a sub-sea installation, i.e. above well heads or pipe lines close to platforms.Another major factor which led to the development of dynamically positioned vessels is the capability o f a vessel to take up station in a matter of minutes and if necessary quickly re-station itself at various points in close proxim ity to a platform, whereas the time to deploy anchors, retrieve them and then redeploy could take many hours or even days.Dynamic positioning control systems typically are used on vessels employed in the following modes of operation:a. Providing support services for offshore

platforms, i.e. inspection, maintenance, fire fighting and accommodation.

b. Coring and drilling.c. Tracking of submersibles.d. Cable laying.e. Trenching and dredging.f. Single point mooring.g. Submarine rescue.

Fig. 2 Modes of Motion

Recent years have seen the development of a new generation of dynamically positioned vessels namely the emergency or multipurpose support vessel (ESV o r MSV respectively). These vessels often combine several modes of operation such as diving support, fire fighting and emergency evacuation and hospital facilities.Details of typical accuracy requirements for DP systems are given in Appendix I.

2. C O N T R O L SYSTEM PRINCIPLE O F O P E R A TIO NThe principle of operation of the control system is relatively straightforward. In o rder to maintain a vessel on station in relation to a fixed point on the sea bed it is necessary to provide input signals from position reference sensors to the contro ller where they are compared w ith the commanded position signal. Based on the

SenW 56STE jAARGANG N R 7 225

error signal between the commanded position and the actual position determined from the reference sensors the controller produces an output signal to the thruster units to reduce the e rror to zero. The controller, which is normally in the form of a computer or microprocessor, controls the X-force (fore and aft), the Y-force (athwartships) and the turning moment N to move the vessel back to the desired position.This simple principle is, however, complicated by the effect of the environmental forces acting on the vessel which have to be taken into account in order to allocate the correct amount of thrust in any given direction. The environmental forces to be considered are due to the waves, sea current and wind.First order wave forces may be high, often exceeding the vessel’s total thruster capacity, and it would not be practical to counteract them. These forces have no effect on the resultant movement of the vessel in relation to a fixed point on the sea bed, since they are of an oscillatory nature. It is therefore necessary for the control system to disregard them and this is effected by filtering the first order wave fre quencies out of the control system.The oscillatory nature of the first order wave effects do, however, have considerable effect on the pitch and roll o f the vessel and fo r certain types of position reference systems which rely on a stable attitude this can create a major source of erro r and accordingly compensation signals are required from vertical reference units to take account of the pitch and roll.The vertical reference units operate like an inclinometer and should be located as close to the centre line of the vessel as practicable.Compensating signals are also required to allow fo r the gusting effect of the wind. Wind gusts can impose a more rapid change in force on the vessel than say the current force and accordingly the control system requires an anticipatory o r feed forward signal in order to take countermeasures against the wind force before the vessel begins to move off station. The wind feed forward signals are derived from wind sensors, combined anemometers and vanes, which provide output signals of

W, W ave filTeI

Thrustercom m ands

Wind direction

M anual inp u ts P itchm easurem ents

Auto? Thruster Thruster C om puterjo ys tic k tran s fo rm con tro l ------ m anual

change o ve r u n it system change over

M anua l p itch references

Fig. 3 Control System Schematic

wind speed and direction. The high frequency components of the wind gusts are filtered out of the control systems.Suitable precautions should be taken when sitting the wind sensors in the proxim ity of helicopter landing areas.To complete the basic control system it is now necessary to introduce the relevant circuits to effect the changeover from automatic to manual together w ith any manual inputs, see Figure 3.To summarise; the performance o f the control system depends upon:a. Response to variation in environmental

forces acting on the vessel.b. Ability to filter out unwanted effects.c. Thruster power available.

3. THRU STER SDynamically positioned vessels usually employ a variety of thruster types. The following are available:a. Lateral thrust units, w ith either fixed or

controllable pitch propellers.b. Azimuth (rotatable) thrust units, with

either fixed or controllable pitch propellers, controlling both magnitude and direction o f thrust.

c. Gil! jet thrust units.d. Cycloidal propellers.e. Fixed o r controllable pitch propellers

(used also fo r transit purposes).

As mentioned previously the DP system controls the three degrees of manoeuvrability of the vessel, i.e. surge, sway and yaw. Typical configurations showing the number and location of thrusters are given in Figure 6.The vessel shown in Figure 6(a) has a poor dynamic positioning capability since it cannot effectively control yaw motions w ithout surge movement.The procedure for the assessment o f a vessel's DP performance capability is based on a static balance of thruster to environmental forces and moments, and as such is nonabsolute in terms of defining the exact position at any point in time, but is an accurate relative assessment of its capability to hold station. These forces and moments have to be balanced by the thruster force and direction, taking into account any interactions such as thruster/thruster, thruster/hull and thruster/current which tend to decrease efficiency. It can be appreciated that if there are several types and/or positions of thrusters, balance, if it is possible at all, may be obtained in an infinite number o f ways, although there is usually only one optimum solution. The purpose of the theoretical procedure is to define that optimum solution for each combination of environmental forces and moments.For a particular system configuration and usable thruster power, there are environmental limits beyond which balance cannot

<B>)

&

6 ( b )

6(c)

D P tA M ) or D P IA A I w i th th ru s te r re d u n d a n cy

6 ( d )

6 ( f )

A z im u th th ru s te r o r C y c lo id a l p ro pe lle r

H T u n n e lth ru s te r

Fig. 6 Typical Thruster Configurations

be achieved and the vessel will move off station. Obviously, in deteriorating weather conditions operations must be suspended or stopped before limiting conditions are reached, not after. This can only be reliably achieved if the limiting conditions are known.Each component of the environmental fo rces acting on the vessel (wind, waves and current) will, depending on its direction relative to the vessel, exert a force and moment tending to bodily move and rotate it from its desired location and orientation.The procedure developed by the Ship Hydrodynamics Group of HNCD has as its starting point some basic assumptions, namely:a. That the problem can be solved by a

static force balance,b. That the sea current is of a fixed veloci

ty which can be set or not coincident w ith the wind direction,

c. That wave conditions, and hence fo rces, can be expressed as a function of wind speed.

These assumptions are necessary in order that capability can be expressed in the normal rosette o r capability diagram form, ty pical examples of which are shown in Figures 4 and 5.


1 5 W ind direction.

285,

27 0

2 5 5

195 165180

.............. All interactions included______ Current interaction excluded_______Hull and current interactions excluded_______All interactions excluded

Fig. 4 Capability plot for example mono-hulled vessel

Current interaction excluded Hull and current interactions excluded

All interactions excluded

Fig. 5 Capability plot for example semi-submersible

An additional assumption in using the static balance approach is that only a certain percentage of the maximum continuous rating o f the thrusters is available fo r the balance, the remainder being necessary for dynamic fluctuations, A figure o f 80% is assumed, which corresponds to the normal level at which the relevant amber alarm warning signal is triggered off in the DP system. The following steps are used within program LRPA 101 to derive the limiting values to draw the capability plot:1. Calculate sea current forces and mo

ments for a fixed current velocity for 15° intervals of current to ship heading. These are calculated using a conventional approach, viz:

F=0.5|)CcAV2

where Cc is the current force coefficient from model tests at the correct Reynolds number.

2. Calculate wind forces and moments for a wind speed of I knot fo r 15° intervals of wind to ship heading using a formula o f the familiar form:

F=0.5pACwAV2w

where Cw are the wind force coefficients obtained from above waterline model tests in a wind tunnel at the correct Reynolds number and representative vertical velocity gradient.

3. Calculate wave forces and moments for an assumed ISSC spectrum, w ith wave height and period defined via speed for 15° interval of wave to ship heading.

Here we are interested only in second order o r wave d rift forces which are obtained via model tests o r using a 2-D potential flow theory program LRPA 103.

4. Sum wind and wave forces and moments at coincident angles of incidence and wind speed.

5. Sum wind and wave forces and moments at current force and moment over the range of angles of incidence of current angle fo r each wind incident angle.

6. Test to see whether thrusters can generate required forces and moments for each current/wind combination, taking account of:-a Thruster/thruster interaction, b Thruster/hull interaction, c Thruster/current interaction, d Dynamic effects allowance (80% MCR).This is done fo r (i) all thrusters in operation and (ii) w ith each thruster out of operation in turn.

7. Steps 2 and 6 are repeated increasing the wind speed by I knot at a time until there is insufficient thrust available to overcome the environmental loads fo r the tw o cases of Step 6.

The above procedure will generate tw o wind speeds for each wind to ship heading to enable the capability plot to be drawn. The balance is achieved using the program LRPA 101, which is an optima! thruster allocation program capable o f incorporating effects due to hydrodynamic interactions between the thrusters and the hull, the

current and each other. Particular features of the thrust allocation such as ’barred zones' can also be included. Power usage can be calculated as well as total thrust, and limiting conditions due to either thrust or power can be ascertained.The importance of the interactions, which is an essential part of the input and is derived either from model experiments o r a data base of suitable information, is illustrated in Figures 4 and 5.The procedure described will be obviously give a clear picture of capability of the DP system, and will also yield tw o minimum values of wind speed (one with all thrusters operating and one with the most effective thruster out of operation). These figures can then be used in conjunction with a cumulative probability/wind speed diagram o r table to indicate the percentage of time that these wind speeds occur in a representative area. These percentages also then define the percentage of time that the DP can hold station against such wind speeds, and this is the Performance Capability Rating (PCR).

Two ratings are assigned:i. To indicate the performance capability

w ith the most effective thruster out of operation.

ii. To indicate the performance capability with all thruster operational.

Typical performance capability ratings for the thruster configurations shown in Figures 6(d), (e) and (f) could vary between 80% and 99% fo r case (i) and be as low as 50% for case (ii) depending on the total


installed power. It will be noted that for the configurations shown in Figures 6(a), (b) and (c) there would be no DP capability w ith any one thruster out o f action thus for case (ii) the rating would be given as zero.

The sitting of the thrusters requires careful consideration. Obviously a prime objective is to produce the maximum moment possible fo r the available thrust, which in simple terms would require the thrusters to be as far apart as possible. This objective cannot always be achieved because account must also be taken of:a. the structural siting of the thrusters within the hull;b. the effect of the wash of one thruster upon another (often referred to as thruster-thruster interaction;c. the effect of the wash from a thruster on the hull (referred to as thruster-hull interaction) and the possible detrimental effects that thrusters could have on the diving complex.

It should be appreciated that different thruster types and configurations have differing response times in relation to the control signals from the DP computer. The compatability of the individual items within the overall system is paramount to the effective operation o f a DP vessel, in par- ticulair the repeatability of the thruster control system.

4. ELECTR IC A L POW ER

4.1 General Arrangem entsThe reliability of the DP system is dependent to a large extent on the electrical power generation and distribution system. Whilst thrust units may have their own dedicated diesel prime movers most DP ships have electrically driven units with centralised electrical generation propulsion and auxiliaries to minimise fuel consumption and engine maintenance. The number and rating of the installed generating sets and the complexity of the distribution arrange

T ra n s fo rm e r 6 .6 kV /4 1 5 VX Circuit bfnnker —( i— Clinch ^ ^ F i r c pump M olor 6.6 k '

Fig. 8 Typical Electrical Distribution Arrangements for Class Notation DP (AA) as fitted on ESV TOLAIR’

ments are dependent upon the specified operational mode of the vessel and the associated redundancy requirements imposed by the Society, i.e. more onerous for a diving support vessel than fo r an offshore supply vessel.The inter-relationship between the power management system and the DP system is important since in environmental conditions greater than calm weather the electrical load is predominantly propulsive. This is shown in Figure 7 which depicts the electrical distribution as fitted to the cable laying vessel 'Northern Venturer' ex ITM Venturer.If on-line generation capacity is matched to demanded load to minimise fuel consumption then large/sudden changes in demanded heading o r the loss of a running generator w ill result in a system overload where the preference tripping o f non-essential load will be insufficient to prevent total system failure. Accordingly the contro l system is arranged to provide thrust limitation in the event of increasing load o r thrust reduction in the event of loss of sup

© 12 5 0 k W m o to r

ply capability. In the event of thrust reduction the vessel will gradually drift off station, usually w ith heading priority, giving the operator time to make a decision and take corrective action.

(«I 8as«c U P S

lb) R«dun<Jant (Dupleti U P S

Fig. 9 Uninterruptable Power Supplies

When even a slow drift off station is critical, i.e. in a diving mode, the correct margin of spinning reserve should be maintained.Deteriorating weather conditions cause an increase in propulsion demand which is supplied by automatic starting, synchronising and load sharing of a non-running generator before the power system reaches the high power alarm setting. The reliability requirements fo r diving operations are such that no single fault may cause total loss o f DP capability leading to more complex power distribution arrangements such as fitted on ESV ’lolair", shown in Figure 8.

Fig. 7 Typical Electrical Distribution Arrangements for Class Notation DP (AM) as fitted on Cable Lying Vessel 'NORTHERN VENTURER’, ex ITM Venturer

4.2 Supply To Control SystemThe electrical power supply to the DP

228 SenW 56STE [AARGANG NR 7

base tine and Super (or Ultra) short base line.

Fig. 10 Long Base Line HPR

te r provides the a.c. supply to the DP contro lle r and monitoring system and the battery provides an emergency standby power source in the event of total main electrical power faillure.An independent a.c. supply, normally derived from the emergency switchboard, is led via a static switch which provides a change over function (make before break) from the inverter to the alternative a.c. supply.The UPS therefore provides a 'no-break' facility in the event of short term interruptions or variations in the vessel’s a.c. power supply system and is necessary to protect control systems with volatile memories that would otherwise be erased in the event of a power failure. It should be appreciated that the ship will d rift off station in the event of a total power failure since the UPS does not provide motive power to the thruster units.

5. P O S IT IO N REFERENCE SYSTEMS

i

The position reference systems are required to provide accurate and reliable measurement of a vessel’s position at any point in time.The vessel’s heading reference is obtained by means of a gyrocompass.Position reference systems are available in many forms and this paper deals w ith the three types of position reference systems most commonly installed i.e. hydroacoustic, taut wire and radio.

5.1 Hydroacoustic Position Reference System (HPR)HPR systems use, as the name implies, an acoustic link between the vessel and a point on the sea bed and are divided into three categories, i.e. Long base line, Short

a. Long base line HPR (See Figure 10).A single transmitter/receiver on the vessel’s hull measures the range to a set of sea bed transponder beacons. It is necessary to determine the relative positions o f the transponders on the sea bed and to achieve this a minimum of three transponders are required.The system determines its position by measuring the ranges to the transponders w ith known relative positions to each other and a sea bed reference point.

b. Short base line HPR (See Figure I I). Short base line systems have an array of transducers (hydrophones) on the vessel’s hull and utilise one sea bed transponder. The realtive time of arrival of the acoustic pulses at the transducers is used to determine the angle o f the beacon in tw o planes and from information o f the pitch, roll and water depth the vessel’s position can be calculated.

c. U ltra short base line HPR (See Figure 12).

Angle n x i im m l as 8 , in a long ships du action ami as 8, In ailiwnitsli>|is dii action

Fig. 11 Short Base Line HPR

Fig. 12 Ultra Short Base Line HPR

Fig. 13 General Arrangement of Hydroacoustic Position Reference System (Ultra Short Base Line)

The ultra short base line is the system most commonly in use on DP vessels and has the transmitting and receiving elements combined in one transducer mounted on the vessel’s hull. The transmitter sends an interrogation pulse (operating on a frequency range of 20 to 30 kHz) to the sea bed transponder and calculates the time to receive the response, accordingly giving the slant range. The phase difference of the received signal is also measured to calculate the slant angle in the X and the Y axes. The pitch and roll of the vessel must also be included in the calculation to offset the tilt o f the transducer face.By measuring the slant range the location of the transponder relative to the transducer can be calculated independently of water depth. The system is most accurate when the transponder is within the narrow beam o f ± 30 degrees. When in wide beam the effective spacing of elements is reduced to cope with the larger phase difference which results in a reduction of accuracy. In addition to the fixed transducer some HPR systems utilise tracking transducers which can be rotated through 360 degrees on a vertical axis and are fitted with narrow beam transmission.The transducer face is inclined at 45 degrees and utilises one of seven ± 15 degree conical beams which may be switched in the vertical plane thereby having the capability of being trained in any direction.As well as ’normal’ dynamic positioning the tracking transducer is used fo r monitoring submersibles (remote operated vehicles) etc, fitted w ith transponders. A typical general arrangement is shown in Figure 13.

5.2 T au t W ireThe taut wire position reference system is perhaps the most simple system employed on DP vessels and consists of a depressor

control and monitoring system is normally in the form of a stabilized uninterruptable power supply (UPS). See Figure 9. The UPS is often supplied as a self-contained unit composed of a charger for the battery and d.c. supply to the inverter. The inver-

W ater depth

yansponder T i in ip o n d t i

SenW 56STE |AARGANG N R 7 229

weight which is lowered to the sea bed on a wire, the means of lowering the weight is normally by a conventional davit. The wire is then maintained in constant tension by means of a hydraulically operated winch and the angle of the wire to the vertical gives the relative position of the weight to the vessel.The wire angles are measured by sensitive inclinometers attached to a guide arm following the wire.If H is the height of the winch from the weight and 0 is the angle of inclination, then:X = H. Tan 0X (fore and aft)Y = H. Tan 0y (athwartships). See Figure 14.A variation on the theme is the horizontal (or surface) taut wire whereby the wire rope is attached to a fixed reference object, i.e. a platform. The wire is then ten- sioned and movements of the vessel in the fore/aft and port/starboard direction in relation to the reference object are detected by potentiometers in the unit.

5.3 Radio position referenceThe most common form of radio position reference system fitted on DP ships is commonly referred to as the ’Artemis’, which is the registered trade mark of Christiaan Huygenslaboratorium B.V. ’Artemis’ uses an automatic tracking microwave link between a fixed station (usually on a platform) placed at any convenient point above sea level and a mobile station mounted on board the vessel and provides measurements of range and bearing o f the vessel from the fixed station.

Fig. 14 Arrangement of Taut W ire Position Reference System

In a measuring situation the microwave automatic tracking antennas are locked to each other setting up a microwave link between the tw o stations. This link is maintained when the mobile unit moves with respect to the fixed unit. The tracking antennas are parallel to each other and perpendicular to the line connecting the centres of the antennas. When the vessel moves the fixed antenna tracks the mobile antenna and the pointing direction of the fixed antenna can be read from the high resolution shaft encoder coupled to the

antenna axis. The reading from this encoder can be electrically adjusted to obtain azimuth values which are referred to, for instance map North, o r any arbitrarily chosen reference direction.The digital azimuth information (angle 0), measured at the fixed station, is transmitted by frequency modulation of the microwave signal to the mobile unit. See Figure 15.To facilitate completion o f the position fix ing operation the distance between the mobile and fixed units is measured, characterised by a short coded interruption o f the continuous microwave transmission at the mobile unit which is detected by the fixed unit. The fixed unit replies with a single interruption, which in turn is detected by the mobile unit. The time lapse between transmitted and received interruption is a measure of the distance and in order to enhance the accuracy the final distance is obtained by averaging thousand or ten thousand time intervals. By determination of distance and azimuth the position fixing of the mobile unit w ith respect to the fixed unit is completed. Values of distance and azimuth are displayed at the mobile unit. An added advantage is that the microwave link can be used for voice communication between the ship and the fixed station by means o f a handset.Signal interruption may be encountered due to passings ships, heavy rain or snow showers, o r dead zones. The positions of these dead zones are very sensitive to the exact height of the antennas above the wate r surface.The use of satellites fo r position reference is, in general, only suitable in applications where navigation of the vessel from A to B with a reasonable degree of tolerance can be accepted e.g. pipelaying o r trenching operations.It is claimed that users of global positioning systems (GPS) which at present can expect accuracies to within 90 metres, w ill be shortly able to achieve accuracies of 30 metres by employing special differential techniques.Satellite position reference using custom desgined GPS precise positioning units are claimed to be capable of defining the position o f offshore vessels to within a few metres.Since some of these systems are still in their infancy it may be some time before the accuracies claimed can be proven.A comparison of position measuring accuracy is given in the following table:

Fig. 15 Radio (Microwave) Position Reference System

6. D E V E L O P M E N T OFC L A S S IF IC A T IO NR EQ U IR EM ENTSThe Society does not associate the classification notations w ith any particular mode o f operation of a vessel, but the natural progression has been that the notation DP (CM) is associated w ith supply vessels, or vessels w ith a relatively simple DP system employing an automated centralised remote manual control system with no redundancy of control system, position reference sensors, environmental sensors and thrusters. See Figure 16.DP (AM) may be assigned to vessels w ith a more complex DP system employing an automatic station keeping system with a manual standby system utilising a compute r o r microprocessor thereby giving redundancy of control. The position reference sensors, environmental sensors and thruster units are to afford a degree of redundancy. The DP (AM) notation was developed to suit vessels operating as cable layers, dredgers, or drill ships, etc. where there is no diving involvement mentioned and a certain amount of latitude in station keeping reliability can be tolerated. See Figure 17.DP (AA). This class notation may be assigned to vessels w ith a fully redundant automatic control system and w ith redundancy o f position reference sensors, environmental sensors and thrusters. This

Position Reference System

Normal Operating Range

Typical Accuracy

Taut W ire up to 300 m water depth 0,5% water depthArtemis 50 m to 10 kms 1,5 m, 2' arcH.P.R. up to 1000 m water depth 1,0% water depthSatellite Geostationary orb it 90 m


providing a risk and reliability assessment i. Print out of any available special tests.of the DP system. An example of FMEA ii. Real time clock.format is given in Appendix II. iii. Memory.

iv. Floating point arithmetic.7. SURVEY REQ UIREM ENTS v. Cassette drive (or equivalent).Details o f the survey requirements are vi. Printer.given in the following sections, namely Fac vii. Buttons and lamps on operator's conto ry Testing, On-board testing, Initial Sur sole.vey at sea, Annual Survey and Special viii. Alpha-numeric display.Survey. ix. Colour display on operator’s console.

X. Analogue input by simulation of thrus7.1 Factory Testing te r pitch.It will be appreciated that one cannot sur- xi. Anaglogue output.

M ic ro w a ve <i*ed s ta tion

Fig. 16 Typical Arrangement for DP (CM) Notation

7.2 On Board TestingA number of the following tests may be carried out while the vessel is undergoing alongside commissioning tests.

notation was developed to suit more exacting DP operations and consideration was given to the relevant National Autho rity1* requirements which specify redundancy requirements depending upon the operational mode of the vessel. The most stringent requirements are of course applicable to modes of operation where, should the vessel inadvertently move off station, human life may be endangered, i.e. diving operations. See Figure 18.The main criteria for a successful DP system is that no single fault should cause a catastrophic failure. This principle forms the basis of the DoE Guidelines fo r diving ships1 and drilling ships2 and is, in general, adopted by the Society for the classification notation DP (AA).

Fig. 17 Typical Arrangement for DP (AM) Notation

The Guidelines' propose that, to ensure that the common mode failure principle is effective, a Failure Modes and Effects Analysis (FMEA) o f the main items of the DP system should be carried out, thereby

* Numbers in superion indicate references

vey a complete DP installation at the factory and therefore testing is usually limited to checking the interface between the controllers (computers o r microprocessors) and the operator console. Testing should be in accordance with an approved test schedule.The following is a typical list of tests that may be readily undertaken at the manufacturer's works.

a. Initial thruster checkout.i. For each thruster motor check start

ing and running on zero pitch.ii. Verify operation of alarms and safe

guards, including emergency stop, for each m otor and hydraulic power pack.

iii. Verify local operation of pitch and azimuth (if applicable) controls.

iv. Verify pitch and azimuth (if appl icable) signals.

b. Limitation of maximum thruster command signal.i. Verify that at the maximum command

signal from the operator console the maximum allowed pitch is reached. Adjust pitch setting gains if necessary

Fig. 18 Typical Arrangement for DP (AA) Notation

xii. Digital input.xiii. Digital output.xiv. Synchro input test.xv. Computer alarm indications.xvi. Power failure tests, by withdrawing

relevant fuses and the corresponding alarms and computer changeover verified.

The above tests are to be repeated for each control computer/microprocessor, where applicable.

SenW 56STE IAARGANG NR 7 231

to achieve this. The vessel should be at its operational draught.

ii. Propulsion thrusters to be set to the lowest value of maximum pitch in the ahead and astern direction.

iii. Verify that at maximum pitch commands the current consumptions do not exceed motor ratings.

c. Rate of thruster pitch change.i. Manually command pitch changes as

quickly as possible and record elapsed tim for:Zero 100% pitch (ahead)100% pitch (ahead) to 100 % pitch (astern)100% pitch (astern) to zero Repeat for each thruster.

d. Thruster signal linearity test.I. Increase pitch command signals by

20% increments to 100% and reduce similarly to zero.

ii. Read and plot curve of command signal versus displacement of blades, servo feed back signals, and motor power current.Repeat fo r each thruster.

e. Rate of change of thruster azimuth angle.i. W ith thrusters at zero pitch, com

mand azimuth changes as quickly as possible for:Zero to + 100% (Port)+ 100% to - 100% (Starb.)

100% to zero.This test should be carried out with the vessel at zero speed, a nominal ahead speed and a nominal astern speed.

ii. W ith vessel at I knot ahead increase azimuth angle from zero, by increments of 25% (maintain constant pitch) to 100% and back to zero.Read and plot curve of command signal versus nozzle angle and feed back angles to observe linearity and hysteresis.Where azimuth thrusters are fitted in lieu o f rudders these tests may be incorporated in the vessel’s trials.The normal shipyard practice is to carry out all the machinery trials prior to the DP trials, accordingly, tests listed above would generally be witnessed prior to the official DP survey.

f. Check the mechanical alignment of the vertical reference sensors and the HPR transducer together w ith the interlock(s) for the transducer i.e. local and/or remote control can only be effected when ship's side valve is in the correct position.

7.3 Survey at SeaDue to the design and operation o f a DP system it is not practical to set up the system in the factory, install it on board the

vessel and expect it to be immediately operable. It is necessary to tune the system during sea trials, prior to the survey at sea, thus taking account of any discrepancies in the signals of pitch and azimuth from the thruster units together with the vessel characteristics that may have been altered since the original design concept.Details of the DP tests are to be included in the approved Test Schedule.The following are indicative of a typical DP installation initial survey.

a. Start up.i. Switch on the UPS in accordance w ith

manufacturers standard procedure.ii. Satisfactory changeover between UPS

and alternative power supply.iii. Load the computers and select one as

’on-line’ and the other on 'stand-by*.iv. ’Key-in’ the time and date,

b. Pre-operational check.i. Initiate lamp test at operator conso-

le(s) to verify illumination of all alarm and indicating lights.

ii. Operate control station transfer switch to transfer control to subsidiary control station(s). Verify transfer is ’bumpless’ and that interlocks are operational, i.e. control may be effected from only one station at a time.

iii. Operate 'Abandon Dive’ switch (if applicable) and check that alarm is in itiated at the Dive Control Station(s).

c. Manual DP control.i. Perform various position and heading

movements using the joystick and ro tate controller and verify vessel moves in the desired direction. Repeat from subsidiary control station^).

ii. Select combination of surge, sway and yaw (i.e. automatic control) and move the joystick and/or the rotate control to verify effect on any modes selected for automatic control.This mode of control is called ’mixed manual'. Repeat from subsidiary control station(s).

iii. Select arbitrary lim it and enter heading alarm limit. Use manual control to change the vessel’s heading in order to initiate the heading limit alarm.

d. Automatic DP control.Change of position and heading set point using a hydroacoustic position reference system.i. Demonstrate deployment of trans

ducer to verify interlocks and position indication from both local and remote control positions.

ii. Deploy sea bed transponders and activate interrogation. Check that symbols appear correctly on HPR screen and that data is displayed correctly at operator console.

iii. Select HPR reference system and initiate a small change in position set point (approx. 20 metres in ’X ’ and ’Y ’ directions and initiate automatic change o f position. Verify that change in position is smooth with overshoot within specific limits for positioning and that heading is maintained within specified limits.

iv. Initiate an automatic change of heading and verify rotation is w ithout overshoot and that position is maintained within specified limits.

v. (initiate a simultaneous change of heading and position and verify overshoot is within limits for positioning and that rotation is w ithout overshoot.

e. Change of position and heading set point using a taut wire position reference system.i. Set up taut wire in accordance with

manufacturers standard procedure, lower taut wire and verify correct display is given on operator console.

ii. Check the limits of the taut wire excursion by moving the vessel forward and aft and then port and starboard until the excursion lim it is reached in each direction and that taut wire 'out of limits’ alarm is initiated.

iii. fnitiate an automatic change of position and heading within the limits of operation o f the taut w ire and verify that the vessel changes position smoothly with overshoot within limits specified and rotation w ithout overshoot.

Care has to be taken when altering heading and/or position to prevent fouling of the taut wire.iv. Initiate alarms associated with taut

w ire hydraulic unit.

f. Change of position and heading set point using radar/ratio position reference system.

I . ’Artemis’.1. Establish the microwave link in ac

cordance with manufacturers standard procedure and correlate the range and bearing with fixes from three prominent landmarkt on a large scale chart of the trials area at tw o locations. This is usually carried out p rior to DP acceptance tests, but should be confirmed.

ii. Examine variance in range and bearing fo r 15 minutes at each location.

iii. W ith the 'Artemis’ as the selected reference system initiate an automatic change o f position and heading and verify that the vessel moves to the new position and heading smoothly and w ithout any significant overshoot.

2. Short range radio position reference.


i. Establish in accordance with manufacturers standard procedure.

ii. Measure position using short range radio system at various locations from the centre o f the axis of a fixed station chain correlating each with fixes from three prominent landmarks on a large scale chart of the trials area. This is usually carried out prior to DP acceptance tests.

iii. Examine variance in range for 15 minutes at each location.

iv. Initiate a position change and verify that vessel moves to the new position smoothly and w ithout overshoot.

g. Operation w ithout position referencesystem.t. In the event of a complete failure in

the signals from the position reference systems the control system transfers to what is called ’model contro l’ and positions the vessel based on the input information prior to losing the signals.

ii. W ith the vessel operating in automatic DP mode with tw o position reference systems on line, deselect the tw o position reference systems thus simulating a complete failure of the position reference signals to the controller.Verify that the vessel can operate for a short period of time w ithout position reference data and that an alarm is initiated to show that the position reference system has failed.Note the time lapse to the alarm, should be in the order of 30 seconds.

h. DP Redundancy tests.I . Gyrocompass.i. Fail one gyrocompass and check that

there is automatic changeover to the stand-by gyrocompasses without any detriment to station keeping capabilities and that appropriate alarm is initiated.Repeat fo r second gyrocompass. A llow sufficient time (about I hour) fo r gyro to stabilise after re-start.

2. Vertical reference unit.i. Repeat procedure given in test (h) ( I).Ii. T ilt one VRU 30 degrees to initiate

alarm, repeat for second VRU.

3. Wind sensor.i. Repeat procedure given in test (h) ( I ).ii. Turn wind sensor vane to opposite di

rection to initiate ’mis-match’ alarm; repeat fo r second wind sensor.

4. Controller.i. Switch off ’on-line’ controller and ver

ify that system changes over to standby controller and that vessel maintains station keeping capabilities. Repeat for the other controller.

j. Electrical supply to controller(s).i. Initiate electrical power failure and

check that the UPS provides electrical supply to control system. The system is to operate for a preset time (nominally 30 minutes) on UPS batteries.

ii. Verify correct voltage and current produced are within specified limits.

iii. Upon restoration of power supply UPS returns to normal operation. Check that batteries are being charged.

k. Thrusters.i. Deploy tw o position reference sys

tems, preferably HPR and Artemis.ii. Set up w ith all thrusters running, DP in

automatic mode and with the head of the ship to the position of least resistance, relevant to the prevailing weather conditions.

iii. When the ship has stabilised perform a manoeuvre as shown in Figure 19.

©

0

g T^ C I 3 @0

c ^ > ®0 \

© 0Fig. 19 Thruster Redundancy Test

I to 2, 2 to 3, 4 to 5 and 5 to 6 are position changes (same heading).3 to 4 and 6 to 7 are heading changes (same position).Hold each position/heading for 5 minutes to stabilise.

iv. When the manoeuvre has been completed, i.e. to (7), trip one thruster and note reallocation of thrust.

v. Repeat the complete manoeuvre with new thrust configuration and at each point of manoeuvre note position and heading deviations. Start and re-select thruster previously tripped.

vi. Trip each remaining thruster in turn and repeat above manoeuvre.

vii. For class notation DP (AM) and DP (AA) the vessel is required to maintain station w ith the most effective thruste r out o f action.

I . Power management tests.i. Trip one running generator and show

that full positioning thrust capability is maintained and that the ship maintains station. If an overload condition occurs pitch limitation is to be carried out and the appropriate alarms initiated.

ii. Restart one generator, either manually o r automatically and verify that

pitch limitation is reduced and the load is rebalanced.

iii. Simulate a single failure of a switchboard section and show that the ship maintains station,

iv. Fail DP system totally and ascertain vessel’s deviation from a given position as the operator changes over to conventional manual control.

m. Endurance test.i. Deploy at least tw o position refer

ence systems and w ith the system in automatic control the ship should remain within its nominated area of operation and heading limits for a period of between 4 and 6 hours, or longer if specified by Builder o r Owner.

7.4 Annual SurveyA t the time of the Annual Survey the operational and maintenance records together with test schedules fo r the DP installation are to be examined to verify that the equipment has operated satisfactorily since the last survey.A general examination of the DP control system and associated machinery items is to be carried out.

7.5 Special SurveyThe requirements of the Special Survey are that the DP control system and associated machinery items are to be generally examined under operating conditions.The following tests would normally be expected to be carried out during the Special Survey:a. Initiate lamp test at operator console(s) to verify illumination of all alarm and indicating lights.b. Operate control station transfer switch to transfer control to subsidiary control station(s) and verify that transfer is 'bumpless' and that all relevant interlocks operate.c. Operate ’Abandon Dive’ switch, if applicable and check that alarm is initiated at the Dive Control Station(s).d. Select manual control and move joystick in ahead, astern, port and starboard directions to show thrust is in accordance with direction selected. Operate turning moment control and show that vessel turns in accordance with the direction selected. Repeat from subsidiary control station(s).e. Initiate a mixed manual test by selecting joystick on manual control and turning moment on automatic control. Repeat by selecting position keeping on automatic and turning moment on manual. Verify that manual control has no effect on selected automatic functions,f. Select automatic control, deploy and put on-line at least tw o position reference systems and then command offsets in both direction and heading. The deviation is to be within acceptable limits specified by Owner/Operator. Allow the system to stabilise

SenW 56STE ]AARGANG N R 7 233

after each command (approximately 10 minutes).g. Redundancy test while on automatic control (for vessels with DP (AM) and DP (AA) notations).i. W ith all thrusters selected and opera

tional, stop the most effective thruste r and verify that the ship maintains its predetermined area of operation and desired heading. Re-start thruster.

ii. Switch off 'on-line' controller; check that there is automatic change-over to the stand-by controller. The ship is to maintain its station keeping capabilities. Repeat fo r the other controller.

iii. Initiate an electrical power failure. The UPS providing electrical power supply to the control station. Verify correct voltage and current produced are within specified limits. Upon restoration of power supply UPS returns to normal operation.

iv. Switch off one position reference system, gyrocompass, vertical reference unit and wind sensor and verify that the relevant alarms are given, the units changeover to the stand-by unit and there is no change in station keeping capabilities.

h. Stop one thruster by means of the independent emergency stop which should override DP control of the thruster. Repeat fo r each thruster.

i. Power management tests.i. Trip one running generator and show

that full positioning thrust capability is maintained and that the ship maintains station. If an overload condition oc-

Op donderdag 11 mei werd de nieuwe vleugel van de Hogeschool voor Petroleum- en Gastechnologie aan het Molenplein I te Den Helder officieel geopend door Prof. dr, L. Reijnders, hoogleraar milieukunde aan de Universiteit van Amsterdam.Dank zij een door de overheid verstrekte bijdrage van bijna 4 miljoen gulden was het mogelijk geworden de school uit te breiden, Na een voorbereidingstijd van twee jaar kon worden begonnen aan de bouw, die zelf ongeveer I 5 maanden in beslag nam.In de nieuwe vleugel bevinden zich met name de praktijklokalen meet- en regeltechniek, elektrotechniek, elektronica, natuurkunde en scheikunde, en het lokaal toegepaste techniek. Verder staan voor de nieuwbouw een ja-knikker en twee boor-

curs pitch limitation is to be carried out and the appropriate alarms initiated.

ii. Restart one generator, either manually or automatically and verify that pitch limitation is reduced and the load is rebalanced.

iii. Simulate a single failure o f a switchboard section and show that the ship maintains station.

iv. Fail DP system totally and ascertain vessel's deviation from a given position as the operator changes over to conventional manual control.

j. Deploy diving complex (if applicable) and operate on automatic control w ith at least tw o position reference systems deployed for a 30 minute period and verify station keeping capability.

8. C O N C L U S IO NThe introduction and development of dynamic positioning controls on board vessels has proved invaluable to the offshore petroleum industry over the last tw o decades as exploration has expanded into more hostile areas.The whole concept of maintaining the position of a vessel above a fixed point on the sea bed w ithout the use of conventional mooring poses problems, but it has been shown that these problems can be overcome using the technology available today. In the future it is envisaged that even more accurate position keeping can be achieved, if this is found to be a requirement of the industry, but perhaps more importantly increased reliability should be the main goal. This may be achieved by the increased use of microprocessors to replace mini-com

vloeistof-silo's opgesteld, die door de Nederlandse Aardolie Maatschappij aan de school zijn geschonken.Aan de school zijn op dit moment 350 leerlingen en 20 docenten verbonden. De leerlingen kunnen de navolgende studierichtingen volgen: boortechnologie,produktietechnologie, onderhoudstechnologie en marien milieutechnologie. 'Noorder Haaks’ is de enige hogeschool in Nederland die deze studierichtingen mag bieden.In 1981 werd aan de toenmalige Hogere Zeevaartschool 'Noorder Haaks’ te Den Helder de studierichting 'Petroleum- en Gastechnologie’ geïntroduceerd. Deze, landelijke, opleiding w ordt gerangschikt onder de noemer 'Algemene Operationele Technologie’ en richtte zich in eerste instantie specifiek op de olie- en gaswinning,

puters and the refinement of position reference systems by, perhaps, the use of satellites.The Society recognises that there is requirement for continuous monitoring of the 'state of the a rt’ w ith respect to DP system in order that the Rules and Regulations keep pace with the changes in technology.

9. A C K N O W LE D G E M E N TSThe Author wishes to express thanks for assistance given in preparing this paper from colleagues in the Control Engineering Department and the Technical Illustrators.The Author also wishes to thank the following companies fo r assistance given and reproduced in this paper.British PetroleumChristiaanen Huygenslaboratorium B.V. GEC Electrical Projects Ltd.Honeywell Shearwater MarineSimrad Albatross Ltd. (formerly Kongs- berg Vapenfabrikk A/S)

10. REFERENCES1. 'Guidelines fo r the specification and operation o f dynamically positioned diving support vessel's issued by the Petroleum Engineering Division of UK Department of Energy and the Norwegian Petroleum Directorate in 1983.2. 'Guildlines fo r the specification and operation of dynamically positioned drilling vessels’, issued by the Petroleum Engineering Division o f the UK Department of Energy in 1982.

het transport van de olie en het gas en de verwerking ervan.In een later stadium zijn de studiedifferen- tiaties 'Onderhoudstechnologie' en 'Milieutechnologie' aan het studiepakket toegevoegd.Bij de differentiatie Onderhoudstechnologie richt het studieprogramma zich in eerste instantie op de olie- en gasindustrie, maar hier geldt in nog sterkere mate dat het arbeidsveld aanzienlijk ruimer is. Binnen de studiedifferentiatie Milieutechnologie loopt als een rode draad door de studie de technische aspecten van het milieubeheer.W at de toekomst betreft is 'Noorder Haaks' nog niet u it de zorgen. Voor I januari 1991 moet de school minimaal 600 studenten hebben. Aangezien zo’n snelle aanwas niet verwacht wordt, is een fusie de enige oplossing. Z o ’n fusie laat wel de opleiding voortbestaan, maar verhuizen vanu it Den Helder is dan niet uitgesloten. En dat is dan weer zonde van de verbouwing.

J. M. V.

UITBREIDING 'NOORDER HAAKS’


NAVTEXdoor Jan Noordegraaf

Fig. I. Navtex ontvanger van Japans model, met voorbeeld papierstrook afgebeeld.

Het vergaan van ’Titanic' gaf de stoot to t verplichte invoering van radio aan boord. Het Duitse motorschip ’Bamberg’ dat op een wrak in het Kanaal liep, omdat de desbetreffende radionavigatiewaarschuwing niet aan boord ontvangen was, was aanleiding to t het invoeren van Navtex, de navigatie- en weerberichtentelex op de frequentie 518 KHz. Vorig jaar verging de ’Maassluis’ voor de kust van Algerije, hetgeen ongetwijfeld zal leiden to t verbetering van de berichtgeving via Navtex in dit gebied. West-Europa heeft hier duidelijk het voortouw genomen, maar elders ter wereld is Navtex-berichtgeving nog niet optimaal, to t in sommige gebieden nog niet bestaand. Er zijn via weersateliieten en -computers op dit moment voldoende gegevens beschikbaar voor een tijdige weersvoorspelling, en het op Navtex zetten daarvan is een kwestie van organisatie. Navtex is inmiddels uitgegroeid to t een internationaal maritiem radio telex systeem, als onderdeel van het Global Maritime Dis- tress and Safety System (GMDSS), gesponsord door de International Maritime Orga- nization (IMO) en de International Hydro- graphic Organization (IHO).Het systeem is opgezet om alle schepen in kustgebieden to t 200 a 400 zeemijl te voorzien van algemene maritieme veilig- heidsinformatie, en de wereld werd door de IMO verdeeld in 16 gebieden, met elk een Navarea coördinator. Zo is bijvoorbeeld de Noordzee en de Oostzee Area I , Biskaje en Westelijk Spanje/Portugal in 2, en de Middellandse Zee Area 3 (zie kaartje in fig. 2).Voorts zijn er 7 typen uitzendingen - zie fig. 3 - die naar behoefte kunnen worden

uitgebreid. Ze bestaan uit A Kustnavigatie- waarschuwingen, B Stormwaarschuwin- gen, C IJswaarschuwingen, D Opsporings- en Hulpverleningswaarschuwingen, E Me- teo-berichten, F Loodsberichten, G Navi- gatiewaarschuwingen, en Z ’QRU' of ’geen berichten’ uitzendingen. De apparatuur bestaat uit een kleine maar elektronisch niet eenvoudige ontvanger, knoppen om vaargebieden en/of zenders te selecteren, printer en een eenvoudige staafantenne met coax verbinding (fig. 4).Het apparaat is gemakkelijk te monteren. Na de invoering van het systeem op de Noord- en Oostzee werd het rijp voor wereldwijd gebruik en dat werd aanleiding to t de ontwikkeling van een Navtex 2 systeem, dat niet alleen West-Europa kan ontvangen. Voor jachten is de prijs inmiddels drastisch gedaald. G rof gesproken be

taalt een jachtenman voor Navtex I (lokaal) ongeveer £ 300,- en de handelsvaart voor Navtex 2 £ 600,-. Dat is zeker voor de handelsvloot een zeer aanvaardbaar bedrag, gezien de voordelen die er tegenover staan. Bovendien w ordt Navtex voor schepen boven 300 ton op I augustus 1991 verplicht, terw ijl bepaalde maritieme sectoren daar allang op vooruitlopen.

Moderne Navtex apparatuur ontvangt berichten selectief, dat wil zeggen niet alleen naar voorgeselecteerd vaargebied, maar om papier te besparen worden dezelfde berichten niet 2 x uitgeprint, te rw ijl de micro-computer foutcorrecties uitvoert, voordat er wordt afgedrukt. Navtex is of w ordt een massa-artikel, met naar te verwachten weinig onderhoud, en gemakkelijk te vervangen.

Fig. 2. Door IMO ingedeelde Area-gebieden ter wereld voor Navtex-berichten.


TransmissionsA t present messages are grouped into seven types but further categories will be added as the system is expanded.

Message typeMessage Type A:

Message Type B;

Message Type C:

Message Type D.

Message Type E:

Message Type F:

Message Type G:

Message Type Z:

Coastal navigation and hazard warnings including buoys out of position, light buoys unlit, new wrecks, floating debris, oil rig moves, naval excercises, etc.Gale warnings: broadcast immediately on receipt from the meteorological office and repeated in next scheduled transmission. These messages may not be rejected when programming the Navtex receiver, ice warnings: in relevant area only i.e. currently North of 62 degrees N.Search and Rescue Alerts: Initial warning of a casualty/vessel in distress is transmitted from the nearest Navtex transmitter. These messages may not be rejected when programming the Navtex receiver.Shipping Forecasts: The pattern of scheduled meteorological information will vary from Navarea to Navarea. A synopsis and area forecast will be available in any sea area within the Navarea.Pilot Warnings: messages issued under this category advise mariners of unscheduled alterations to offshore pilot stations e.g. due to the weather.Navaid Warnings: warnings o f problems in the electronic navigation chains including Decca, Loran C, Omega and Transit satellite systems (Satnav).Letters ’QRU’ (no messages) may be broadcast when applicable to confirm correct operation of receiver.

Fig. 4. Navtex 2. Afmetingen van de apparatuur.

Navtex kan, bij een goede updating vanaf de wal, een grote hulp en zegen zijn bij de navigatie. Voortgekomen uit de TOR - Telex Over Radio - kan zij aan boord, naast de eigen weerschrijver, zwart op w it onschatbare diensten bewijzen voor een veiliger vaart, want de zee blijft onberekenbaar en als haar luimen en buien w orden voorspeld, kan de zeeman daar zijn voordeel mee doen.

Fig. 3. Transmissions. Uitgebreide Engelse/internationale lijst van soorten uitzendingen.

Nieuwe uitgaven New Issues

Nieuw e studiegidsOnlangs is de nieuwe studiegids Opleidingen Werktuigbouwkunde van Koninklijke PBN A verschenen. De informatie is zowel voor cursisten als opleidingsfunctionarissen nog beter toegankelijk geworden. Nieuwe schema’s geven de samenhang van opleidingen weer. Studieprogramma’s en vrijstellingen worden waar nodig per cursus in tabelvorm gepresenteerd.Nieuwe opleidingen in deze gids zijn: Werkvoorbereiding, Tijd- en kostencalcu- latie, Flexibele produktieautomatisering, PLC's, Schakeltechniek en PLC’s, Bestu- ringstechnologie en Onderhoudstechniek. De Basis-, Middelbare en Hogere Opleiding Werktuigbouwkunde zijn geheel herzien. Bij de middelbare en hogere opleiding zijn de afstudeermogelijkheden aangepast, zodat de consistentie met het reguliere onderwijs verbeterd is.Ook de tekenaars-constructeursopleidin- gen zijn bijna alle geheel herzien.

U kunt vrijblijvend een exemplaar van deze studiegids opvragen bij Koninklijke PBNA, Postbus 9053, 6800 GS Arnhem, tel. 085-57591 I.

Naam lijstHet bestuur van de Stichting Naamlijst In

genieurs Rijkshogeschool Groningen wil hierbij alle belangstellenden er van in kennis stellen dat de tweede, sterk gewijzigde, druk van de naamlijst verschenen is. Oorspronkelijk opgezet in 1984, om een naamlijst op te stellen van afgestudeerden van de gemeentelijke H.T.S. te Groningen heeft de stichting na I augustus 1986 haar gebied uitgebreid.Per die datum is de H.T.S. van de gemeente Groningen opgegaan in de Rijkshogeschool Groningen en vorm t samen met de vroegere Analistenopleiding en met de vroegere Hogere Zeevaartschool te Delfzijl nu de technische sector van deze Hogeschool.De lijst bevat nu dus samen van afgestudeerden van H.T.S. Analistenopleiding,H.Z.S. en R.H.G., allen voor zover ze volgens de wet de ing.titel mogen voeren. Exemplaren kunnen verkregen worden door overmaking van f 15,- op girorekening nr. 5639080 t.n.v. penningmeester St. Naamlijst te Spijk (Gr).Afgestudeerden van bovengenoemde instellingen die opgenomen wensen te w orden in de volgende editie, worden verzocht naam en adres te sturen naar St. Naamlijst, Postbus 3037, 9701 DA G roningen of te bellen naar de administratie van de Technische Sector tel: 050-731600.

V » »

ÄPBNA

236 SenW 56STE IAARGANG NR 7

NOISE LEVELS AND NOISE CONTROLON SMALL AND MEDIUM SIZED FISHING VESSELS*

by ir. F. A. Veenstra**

AbstractBecause there are no statutory noise regulations for fshing vessels, the resulting noise levels hove been mostly accepted as the state of the art and common practise in the shipyards. One should inevitably live with the high noise levels, particularly onboard of the small upto medium sized fishing vessels. Even some fishermen appraised the noise: ’Shipnoise means power and fishing effort'.From a health and safety point of view (hearing damage, well-being crew), an increasing number of Dutch skippers/owners asks for an acceptable acoustical environment in the working and living spaces, however without excessive cost-effects. With reference to the ship acoustical experiences onboard the larger Dutch vessels, nowadays noise levels of 60-65 dB (A) are be considered as acceptable in the accommodation spaces and even required for the merchant marine vessels (IMO noise limit requirements).Fishing vessels are hardly to be compared with the larger merchant marine vessels. Specific noise measurements are required here and cooperation with ship acoustical engineers with regard to existing shipboard noise control techniques should be emphasized. From the acoustical point of view the major fishing vessels, particularly the small to medium sized overpowered Dutch beamtrawlers, have an illogical arrangement, viz. the working and living spaces are to close too the dominant noise sources.Based on the measurements and comparative studies of the last five years in the Dutch beamtrawler fisheries, even for newbuilding vessels the noise levels can be reduced with 5-IOdB(A) without radical changes in the layout and design (fishing effort), resulting in accommodation levels of 65-70 dB (A). Because the costs will play a dominant role in the ultimate noise control measurements, various noise control packages are given with costs in relation to attainable noise levels. Final application will depend on the skipper/owner requirements and (near) future noise regulations.

1.1. S T A T U T O R Y N O ISE R E G U LA TIO N S

1.1.1 IntroductionUp to now fishing vessels have been excluded from the statutory regulations or recommendations, international such as the International Maritime Organisation (IMO) ’Code on noise levels on board ships’ as well as national such as the ’Regulations preventing noise annoyance onboard ships’ of the Dutch Shipping Inspectorate (SI) for merchant marine vessels. Due to the growing awareness of the importance of the general working and living conditions onboard fishing vessels, there is reason to believe that fo r newbuilding vessels stricter noise recommendations or even limits have to be met in the nineties (EC-labour legislation and/or IMO regulations).

1.1.2. Acoustical environm ent onboardToo high noise levels are undesirable and unhealthy, also onboard fishing vessels:- it may cause hearing damage (health);- it makes verbal communication difficult

and hearing of audible alarms (safety):- it may cause fatigue and stress (working

conditions).

As reference the IMO/SI noise limits for

* Paper presented at the World Symposium on Fishing Gear and Fishing Vessel Design, Nov. 21-24 1988 at the Marine Institute St John’s New Foundland Canada.** Head of the Technical Research Department of The Netherlands Institute for Fishery Investigations (RIVC), IJmuiden. The Netherlands.

newbuilding vessels other then fishing vessels w ill be followed here:- accommodation spaces 60 dB(A)- messrooms 65 dB(A)- wheelhouse 65 dB(A)- engineroom (unmanned) I 10 dB(A)

The noise readings are decibel measurements with a A weighing filter in accordance with the normal human hearing mechanism.

1.2. D U T C H F IS H IN G VESSELS

1.2.1. IntroductionThe Dutch fisheries can be characterised in three types o f fishing vessels, mainly designed and built by national shipyards:

fishing cutters:• length 24-45 m (220-3000 kW)• demersal and small pelagic fish (flatfish,

shrimps, herring, cod, whiting)• North Sea• number 600 ( 1987)• employment 3000• value landed fish 750 1 06 Dfl.

mussel/cockle dredgers• length 30-35 m (200 kW)• mollucs on/in the seabed (mussels and

cockles)• coastal/estuaries North Sea• number 100 (1987)• employment 400• value landed mollucs 100 106 Dfl.

deepfreeze sterntrawlers• length 75-1 10 m (3000-6000 kW)• pelagic fish (herring, mackerel)• North Sea/Atlantic Ocean

• number 15(1987)• employment 300• value landed fish 150 106 Dfl.

As in the Dutch fishing industry a fishing company with more than 3-5 vessels is an exception, a company oriented design approach is absent. Every skipper/owner prefers his own shipyard and/or designer. Once a good vessel design is build, many newbuildings followed with the skippers adjustments and with often increased main dimensions. So that although the main features (layout, fishing method) of these vessels are the same, hardly tw o ships can be found w ith identical installations and equipment.From the above mentioned types, the fishing cutters, mostly beamtrawlers, have very difficult design features from the acoustical point of view: a smaller upto medium sized fishing vessel, overpowered in relation to the main dimensions and with the dominant noise sources adjacent to the accommodation and working spaces.

1.2.2. Beam trawlersIn figure I (general arrangement) and figure 2 (beam trawling) it can be seen that the applied fishing method dictates the layout to a greater extent. All beamtrawlers are towing tw o trawlnets by means of booms (or outriggers) perpendicular to the shipsides. The characteristic construction is a single deck hull with design trim (max. propeller diameter) and extended forecastle (fish handling) and aftward the accommodation (4-7 persons).Below the maindeck the hull is often divided in:

SenW 56STE JÀÀRGANG N R 7 237

- fore peak- fish hold (+0"C )- net store- engine room- crew ’s quarters- aft peak

In the engine room a medium or high speed diesel engine is installed which drives coupled to a reverse and reduction gear a fixed pitch nozzled propeller, designed for the fishing condition, maximum pull at 4-7 knots. Often the D.C. main supplies electricity to the fish winch and bowthruster while the A.C. main is indispensable fo r the auxiliaries. Both mains are generated independently, either diesel engine driven {high speed) and (partly) or diesel main engine driven (pto). The fully automated cool- and crush ice unit is installed in the fish hold. The beamers are designed and built according the Rules and Regulations of the Dutch Shipping Inspectorate for seagoing fishing cutters.

1.2.3. Acoustical design aspectsSound in ships, also fishing vessels, is mainly determined by the machinery propulsion plant and the auxiliary engines. Noise (sources) are distinguished in the way sound propagates from the source to its surroundings, either by air = airborne noise and/or by ship structures = structure borne noise. Separating decks and bulkheads are excited by both noises. The vibration of these structure parts will then be propagated to the boundaries o f the accommodation, which w ill radiate noise into the crew’s living and working spaces. The more separating construction are installed the easier and less expensive noise control w ill be.However a luxury fo r the small upto medium sized fishing vessels with the dominant noise sources adjacent to the accommodation (figure 3).

Based on the extensive measurements onboard beamers the primary acoustical aspects to be considered are:- main propulsion engine- gear box

Figure I General Arrangement bram trawler

- propeller- diesel generator sets

And to a lesser extent the winches and hydraulics. Except incidental application of resilient mountings of the diesel sets, no explicit noise control measures have been taken. One should inevitably live w ith the high noise levels.

1.3. N O IS E M EASUREM ENTS

1.3.1. Survey methodIn the past five years The Netherlands Institute for Fishery Investigations (RIVO) has been taken noise measurements onboard ca. 50 beamers, during sea trials as well as during fishing.Initially as decibel noise readings with a A- weighing filte r and later also octave band analysis. For this a precision grade sound level meter, Bruel & Kjaer, type 2230 was used w ith calibration before and after each series o f measurements.Because of reproducible noise data which is comparable w ith noise readings onboard ship types accoustical similar to fishing vessels, the measurements have been carried out in accordance w ith the Recommendations of the Dutch Shipping Inspectorate for merchant vessels.

Based on the first RIVO measurements a cooperative contract research project was started in 1986 and finished in 1987 by RIVO (fishery engineers) and the Ship Acoustic Department o f the Institute of

Figure 2 Beam trawling

99 85

» 1 725

85

Figure 3 Noise measurements accommodation [dB(A) values]

Applied Physics TNO -TH (acoustical engineers), which institute has a long experience onboard a.o. coastal merchant marine vessels, tug- and workboats, more or less acoustical simimlar to fishing vessels.By means of quayside and steaming measurements onboard tw o representative beamers the airborne and structure borne sound transmission paths were investigated (figure 4) and also the relative contributions of the dominant noise sources. The TPD-TNO measurements are containing sound pressure and source velocity levels.

1.3.2. Noise LevelsIn Figure 5 the noise levels of 20 beamers have been given in dB (A) with in figure 3 the noise readings fo r a 1500 kW (2000 hp) beamtrawler. For this representative beamer also some sound pressure levels in dB (octave bands) can be seen in Figures 6-7. Both fo r the steaming conditions and in the following locations:

(1) messroom/galley (75-80 dB(A))(2) accommodation/

cabin (75-82 dB(A))(3) wheelhouse (70-77 dB(A))(4) engineroom (107-1 12 dB(A))

Between parenthesis the major and characteristic group o f dB(A) values are mentioned.W ith reference to the IMO and Dutch SI noise limits (60-65), the noise measurements are 10-15 dB(A) higher fo r the accommodation spaces.

1.3.3. Noise ContributionsIn the first place the structure borne noise from the hardmounted propulsion diesel adversely impacted all the living and operating spaces, particularly in the low frequency range 63-125 Hz. The main cause fo r propeller induced vibration and noise is pressure fluctuations on the aftship hullform, propagated by the ship structure and radiated as airborne noise in the receiving spaces. The diesel generator sets are already often resiliently mounted and have no explicit contribution to the high


propeller noise airborne noise machinery structure born noise machinery

H M*«room/g»n«g Accomodation/cabi E3 Vh»«tv>us* CD Engin* room

115

105

95

1 2 Ï 4 5 6 7 8 9 10 tt 12 13 14 15 16 17 18 19 20 MO/SI

Figure 5 Noise measurements onboard Dutch beamtrawler (dBLA) values)Figure 4 Sound transmission paths

noise levels. The same concerns the gear box, steering gear, compressors and the ventilators. The airborne noise from the engine room as well as the exhaust system to the adjacent spaces is far less representative. However in the wheelhouse the airborne noise in the higher frequencies and from the exhaust system have an important contribution.

1.4. N O ISE C O N T R O L

1.4.1. IntroductionFor an effective noise control the measures to be taken should be considered in an early design stage and supervised adequately during the building and fitting out phase of the vessel. Curing afterwards is always very difficult and expensive to which it is mostly impossible to solve the basic (acoustical) errors.

Noise control treatment can be done in three ways, viz.:- at the noise sources- in the sound transmission paths- in the receiving compartments

The measures at the sources have the great advantage o f effecting the receiving spaces simultaneously w ith one package. The measures in the transmission paths and the accommodation only have their effect in the controlled compartments. Therefore especially the measures at the sources should be studied carefully to obtain the maximum result, including the selection of machinery with minimum noise source levels. The quietest machine fo r a given performance gives a significant improvement. Besides a thorough noise prediction in the design stage gives the essential data fo r selecting the major effect areas for noise control packages, of which sources and transmission paths are responsible for excess of requirements.Up to now it is a common beamer design practice to apply the measures mainly in the accommodation areas (receiving spaces), to which the skipper-owner does not want any radical changes in the general layout and machinery setup. From the

SenW 56STE [AARGANG NR 7

acoustical point of view a very illogical arrangement:- the most noise sensitive compartments

are located between the major noise sources, the propulsion diesels and propeller:

- the aft engine room bulkhead and the exhaust uptakes are directly separating the machinery spaces from the accommodation;

- the exhaust and intake openings are very closely located near the wheelhouse and accommodation.

1.4.2. Noise control packagesBased on the traditional beamer layout (figure I ) and the absence o f statutory noise regulations fo r fishing vessels four noise control packages are given to attain design

noise level limits of:1. 75 dB(A), max. 80 dB(A)2. 70 dB(A), max. 75 dB(A)3. 65 dB(A), max. 70 dB(A)4. 60 dB(A), max. 65 dB(A)

Noise control package I (75 dB(A), max. 80 dB( A ))These noise levels are already common practice for various Dutch shipyards. To which only measures were taken based on the IMO fire protection regulations for fishing vessels (BI5/A30 decks and bulkheads with carpentry).However for a conceptual noise level limit of 75 dB(A) the following additional noise measures should be taken in the receiving spaces:la. non combustible floors to be ap-

Figure 6 Sound pressure levels in messroom (dB-values)

100

90

eo

70

SO

SO

40

dB t . o . v . 2 .1 0 Pa ( 1 /3—o c ta v e n )

/

i '

\ t^ 3 *

01

\NC

41 .5 63 125 250 500 1K 2K HZ

f r e q .

©— © 6915 main engine, id le , 850 rev's/min.a a 0O7/1 steaming, 750 rev's/m in.H 1- 9926 steaming, 850 re v ' s/min.

HZ

O— 3 6932 993b

main engine, id le , 85O rev fo/min*

afceaming, 850 re v ' a/min..

Figure 7 Sound pressure levels in engine room (dB-values)

plied as a semifloating floor system;I b. decoupling of non combustible lin

ings and the hull deckhouse construction as much as possible but at any rate in the living space below deck decoupling of the floor and aft bulkhead;

Ic. application of absorbent material,c.q. mineral wool behind the linings and w ith a relative heavy specific weight.

Besides the engineroorn boundaries should attenuate the airborne noises down to 70 dB(A).

Noise control package 2 (70 dB(A), max. 75dB(A ))Reducing the noise level limits in the accommodation w ith 5 dB(A), from 75—»70 dB(A), the measures in the receiving spaces should be extended and completed with some measures in the sound transmission paths:2a. complete floating floor (figure 8); 2b, acoustical decoupling of floors, lin

ings and ceilings from the construction (figure 8);

2c. application o f absorbent material in airgaps behind linings and ceilings and upper engine room cladding;

2d. flexible connections o f pipes, especially the exhaust pipe, between the diesel engines and the above laying deck;

2e. installation of a correct chosen exhaust silencer (type, dimensions, configuration), resiliently mounted in the engine room uptakes (figure9).

Besides the engine room boundaries should attentuate the airborne noises down to 65 dB(A).

Noise control package 3 (65 dB(A), max. 70 dB(A )).Reducing the beamer noise levels with another 5 dB(A), from 70—»65 dB(A), additional measures to package 2 should be

taken, viz. extended attenuation in the transmission paths and measures at the noise sources:3a-3e. package 23f. stiffening of engine and shaft coupl

ing foundation;3g. stiffening of the hull scantlings above

the propeller;3h. only flexible connections between

aft engine room bulkhead and the propulsion machinery;

3i. only flexible piping and wiring connections between the diesel engines and the above laying deck and also the machinery foundation;

3j. resiliently mounting of the diesel generator sets;

3k. resiliently mounting of the propulsion diesel (figure 10).

Besides the engine room boundaries and

Figure 8 Floating floor system

Figure 9 Resiliently mounting of exhaust silencer

floating floor systems should attenuate the airborne noises down to 60 dB(A) which can only be attained by carefully application of package 3.

Noise control package 4 (60 dB(A), max. 65 dB(A ))For this type of fishing vessel (layout, machinery setup) it is almost impossible to attain noise level limits of 60 dB(A) in the accommodation spaces particularly in the living quarters below deck.Either additional to package 3, acoustically optimising o f the propeller and aftship hull form and structure o r instead o f measures at the sources resiliently mounting of the complete deckhouse is necessary.Both solutions imply extensive research before beamer application is coming up for discussion.4a-4k. package 341. an acoustical optimised propeller

and natural frequencies/responses of the aftship hull construction or instead o f package 3 and 4.

4 alternative)resiliently mounting of the complete deckhouse.

1.4.3. Costs in relation to noise levels.Along w ith all technical details the costs will play a dominant role in the potentional noise control packages. Especially fo r the fishing vessels because of absence of noise requirements, but there is reason to believe that fo r newbuildings this will change


design

dB/A)

noise control measures newbuilding D fl. 6.000.000

goal inreceivingspaces

intransmission

paths

atsources

*additional

extra inve< Dfl.

tmentspercent

75-80 - - - - - -

75 package 1 20.000 0.3

70 package 2 --->70.000 1.2

65 package 3 120.000 2.0

60 package 4 > 150.000 >2.5

* optimum propeller/aftship hullform and -structure or a resilicntly mounted deckh.

in the near future owing to the increasing E.C. and Dutch Labour Regulation onshore as well as offshore. Before an economical choice can be made in providing an acoustical acceptable environment on board the beamers, a better understanding is needed o f the costs in relation to the noise levels and total investment of a modern beamer of 1500 kW (2000 hp) in 1988, viz. Dfl.6.000.000.-.In table I the costs in relation to the four noise packages have been given. The here mentioned extra investments are including increased engineering and supervision hours for the first newbuildings but w ithout accompanying of an acoustical engineer.Similar to other vessel types the costs involved in noise reducing measures increase exponential w ith the noise reduction achieved. However limited to the design goal of 65 dB(A), one can speak of an economical cost-benefit solution. Reducing the accommodation noise levels with another 5 dB(A) leads to unknown acoustical and cost aspects but particularly to radical changes in the beamer design. This

Figure 10 Resiliently mounting of medium speed propulsion diesel

can result in declining fishing efforts, e.g. less propeller performance owing to an acoustical needed greater tipclearance. The same can be said about the alternative: resiliently mounting of the complete deckhouse, a very expensive technical solution (at least Dfl. 100.000,-) w ith great disadvantage, e.g. annoyance crew and extra maintenance costs.Before these additional measures are coming up for discussion, extensive research is needed to prevent excessive, unnecessary and even non-effective measures which will change the fishing effort of the Dutch beamer considerable.To the authors opinion a beamer design goal o f 65 dB(A), max. 70 dB(A) is an economical and acoustical acceptable solution w ithout radical changes in the tradi-

Table I Costs in relation to noise levels.

tional but very effective beamer design. This means a cost-increase o f ca. 1-2% of the total newbuilding investment,

1.5 ConclusionsAlthough there are not Dutch or international noise level requirements for fishing vessels, the measured noise readings (75- 80 dB(A)) are clearly showing that nobody can speak of an acceptable acoustical environment onboard of the Dutch beamers (well-being, hearing damage, safety).Up to now these resulting noise levels are accepted as the state of the art w ith no economically acceptable and well proven solutions.One should inevitably live with the high noise levels and even some fishermen appraised these levels: 'Shipnoise means power and fishing effort’.However things are changing, on the one hand side owing to more knowledge of the noise levels (state of the art, RIVO) and noise control possibilities (economic and reliable solutions, RIVO, TPD/TNO) and on the other hand anticipating the inevitable (near) future requirements (shipyards), but also more skippers are asking fo r lower accommodation noise levels (crew annoyance).Based on the experiences and comparative studies of the last four years and seeing the acoustical progress made onboard of similar vessels, one may conclude that for fishing vessels also acceptable noise levels are attainable, fo r reasonable costs in relation to the total investment, viz. 1-2%. To which no radical changes in the beamer design are necessary with accommodation noise levels o f 65-70 dB(A). To the authors opinion leads a further reduction of the noise levels to an excess of costs and ex

cess o f intervening in the beamtrawling fisheries.

Acknowledgem entThe author would like to thank all shipyards, especially Visser (Den Helder), Maaskant (Stellendam), Padmos (Stellen- dam), Metz (Urk) and Damen (Gorin- chem). Also the skippers/owners and crew, who kindly placed their fishing vessels at our disposal fo r noise measurements. Besides the author wants to express his gratitude to TPD/TNO, the Shipsacoustics Department, especially to Mr. M. J. A. de Regt, the acoustical engineer of the beamer noise control packages.

References1. Noise levels and sources onboard Dutch

fishing cutters, ICES paper CM! I987/B:2I, Fish Capture Cttee by F. A. Veenstra, Netherlands Institute for Fishery Investiga- tions-IJmuiden.

2. Marine Engineering and noise control, S en W 54-2, 1988, Institute of Applied Physics TNO/TH-Delft, Holland, by H. F. Steenhoek.

3. Noise control in Tug design, a theoretical and practical approach, Damen-Shipyards, Gorinchem Holland by j. Jansen.

4. Manual on shipboard noise control, 1984, Institute of Applied Physics TNO/TH-Delft, Holland, by J. Buitens and M. J. A. de Regt (in Dutch).

5. Noise levels on seagoing fishing cutters, part I, II, III. CMO I986/B.5.4., by M. J. A. de Regt (in Dutch).

6. Economical noise control on Dutch beamtrawlers, ICES paper CM 198/B: 14 Fish Capture Cttee by F. A. Veenstra, Netherlands Institute for Fishery Investigations, IJmuiden,

SenW 56STE |AARGANG NR 7 241

NOTES ON HARBOUR TUG DESIGNBy ir. F. Kok

Wijsmuller is one of the well known Dutch towage and salvage companies. Heavy lift transportation is one of the many specialities. Its newbuilding and construction department was transformed into a subsidiary in 1981: Wijsmuller Engineering B.V., which is not only responsible for the research, development and engineering on behalf of the other companies within the Wijsmuller group, but is also acting as a consultant to shipbuilders, shipowners and operators all over the world. This article focusses on some aspects of the design philosophy of Wijsmuller Engineering, especially in connection with harbour tugs, and concentrates on some of their more recent projects.

DESIG N P H IL O S O P H YIn this chapter some remarks are made on the design process in general and on drawing up specifications fo r a harbour tug in particular.

T H E D ESIG N PROCESSDesigning is defined here in a general sense as: finding the optimum solution to satisfy a given demand w ith the aid of available means and taking into account physical constraints and social standards.Generally the design process is divided into three phases.When the process starts, the demand is often described in very general terms ( ’We need another tug1) and a considerable amount of study and analysis may be necessary to specify the demand in sufficient detail. This is the first phase of the design process, resulting in a functional specification which is the basis for the next phase.The second phase is finding solutions which will satisfy the functional specifications and selecting the best one.

If the demand is for a tug, this phase will result in a specification of the tug’s dimensions, machinery installation and arrangement in sufficient detail to make a reasonable estimate of costs possible, to request tenders and to negotiate a building contract. The second phase is often referred to as the design phase; it is clear that ’design’ is used here in a restricted sense.The third phase comprises detailing the chosen solution into complete building specifications, shop drawings, etc. This phase of the process is referred to as the engineering phase.A more extensive description of the design process is given in [ I ].

Specifying the demandWhen drawing up the functional specification for a harbour tug, the total situation in the port in question has to be considered. Important aspects are:- the size and type of ships calling at the port and their numbers;- the type of port and the prevailing geographical and climatic conditions;- the tugboat services already available. These and several other factors are described in detail in [2], The next paragraphs are based on that publication.In very general terms, the demand is fo r a tool to assist seagoing ships when they ente r or leave port. The ships are then quite limited because they have to sail at a reduced speed and that obviously results in less manoeuvrability than at sea, so an external force is required to move them in the right direction or to bring them to a stop.Bollard pull and manoeuvrability appear to be the main requirements fo r harbour tugs, which have as main activities:

- harbour towage, including;- berthing/unberthing vessels;- assisting ships and shipyards;- river o r canal towage, when the port is situated some distance inland, as is the case with many older ports.For economic reasons these activities have to be performed with a minimum crew. How great the bollard pull should be depends mainly on the size of the vessels, i.e. their displacement, but other factors, such as the type o f vessel, may be o f influence. Ships with high superstructures, e.g. passenger vessels and car carriers, are wind sensitive and a greater bollard pull may be required, especially where local conditions include strong winds.Also in the case of ships carrying dangerous cargoes, a greater bollard pull may be required to provide a sufficient safety margin.Offshore structures, like drilling rigs, are a class apart. The bollard pull required is derived from experience, calculations and/or simulations though it is not necessary, not desirable even, that the total bollard pull required to control the tow, is supplied by a single tug. Often tw o or more tugs are used, that also increases the manoeuvrability of the tow.Various size ships call at the port and that requires tugs with different bollard pull capacities. Therefore, when deciding upon the required bollard pull for a specific new tug, it is quite necessary to take the already available port capacities into account. Concentrating not only on one’s own fleet but also on the fleets of possible competitors.Good manoeuvrability is a requirement for any harbour tug, especially now many modern merchant ships, being equipped w ith side thrusters, have improved manoeuvring characteristics. To be of any use, tugs must be able to manoeuvre quicker and easier than their tows. Local circumstances can make good manoeuvrability even more important: relativedly narrow fairways, possible w ith difficult bends, locks and bridges which have to be passed, narrow entranches to harbour basins, etc. The number o f crew depends on the duties which the tug has to perform and on the equipment installed.Very often harbour tugs are equipped for additional duties to increase their usefulness and their earning power.These additional activities may include one or more o f the following:- firefighting;

Foto: Henk Koning

SenW 56STE |AARGANG NR7

- rescue/stand-by operations;- salvage;- pollution combat and control;- maintenance of buoys etc.;- hydrographical work;- pilotage.Some of these tasks may be imposed by the harbour authorities concerned.Also many harbour tugs are equipped for: coastal towage and further activities at sea, such as:- escort services;- anchor handling;- supply services;- crew tendering.in some ports there is a need for:- ice breaking.Each of these additional activities brings its specific requirements as regards equipment, accommodation etc. The functional specification must describe the additional tasks which the tug has to perform and the requirements as regards the capacities of the systems concerned.The services which are required from the tug and the relative importance of each of them determine the operation methods to be used and the towing gear needed:a. towing, w ith the tow line secured to:

• towing bitt;• towing hook;• towing winch;

b. pushing;• fendering;

c. push-pull operations;• a. combination o f a. and b.;

d. along side towing;• long tow lines secured either fo rward o r aft.

Each operation method had its own application:a. Towing is usual at sea and when rela

tively long distances have to be covered on canais or rivers.

b. Pushing and in particularc. the push-pull type of operation are very

suitable fo r berthing and unberthing vessels.

d. The along side towing method is used sometimes when rendering assistance at sea and there is no direct need for the tug to pull.

It is essential that the operation methods to be adopted are discussed in this phase w ith all concerned: not only the owners, but also tug crews, pilots and port authorities.Further elements to be included in the functional specifications are:- free running speed; in some cases, depending on the additional duties which the tug has to perform, speed may be an important point in the design procedure, e.g. when rescue is one of the duties;- the number of crew members;- bunker capacity;- possible restrictions on the tug’s main dimensions, not only from the operational point o f view, but also in regard to the

available drydocking possibilities, which sometimes restrict the tug’s dimensions (mostly the draught) and/or weight;- class.In some cases the budget which is available fo r the new ship is limited and the designer should then be informed about the maximum budget.

The design phaseOne of the most important aspects in tug design is the selection of the propulsion system. Options are:1. conventional propellers;2. rudder propellers, also referred to as

azimuth thrusters o r z-pellers;3. cycloidal propellers.

Both the conventional propellers and the rudder propellers can be provided with nozzles to increase bollard pull and with pitch control to facilitate manoeuvring and to obtain optimum propulsive efficiency over the entire speed range of the tug. Rudder propellers and cycloidal propellers are superior to conventional propellers as regards manoeuvrability. These propulsion units can be arranged at the stern as well as in the forward part of the ship. In the first case the tugs are of the ’stern drive’ type, in the latter case of the ’tractor’ type.

W ith all three types of propellers one or tw o propulsion units can be fitted, but w ith rudder propellers and cycloidal propellers tw o units are usual.In all their recent projects Wijsmuller Engineering have preferred rudder propellers. This because o f the superior manoeuvrability as compared to that of conventional propeller tugs and because a rudder propeller has a higher efficiency than a cycloidal propeller.In all cases nozzles are fitted to increase the bollard pull. For instance in some cases pitch control has been adopted. All projects have tw o propulsion units fo r increased manoeuvrability, to reduce the draught and to enhance safety and flexibility.Both stern drive and tractor drive have been applied in the projects, although Wijsmuller Engineering prefer stern drive for a number of reasons:- stern drive tugs are better manoeuvrable when acting as a bow tug;- tractor drive tugs have a larger draught;- stern drive tugs have a better performance in a seaway;- in principle maintenance of the rudder propeller units of stern drive tugs is easily possible w ithout drydocking the tug, if hatches have been provided in the upper

SenW 56STE jAARGANG N R 7 243

deck to lift the unit from the water; such provisions are not feasible in tractor drive tugs.The next step is to determine the engine power required. This is calculated with the formula:engine power in kW = f * bollard pull in tonnes,where f = 52.5 to 62.5 for rudder propeller tugsand f = approx. 67 fo r tugs with cycloidal propellers.When the engine power is known, a suitable type of rudder propeller can be selected. The type and size of the rudder propellers determine the minimum breadth of the tug, the draught, the heigth of the deck in the aft ship and thus the minimum depth, the shape o f the aft ship sections and the length of the thruster compartment.The length is determined on practical considerations. First the minimum length of the engine room is determined on basis of the dimensions of the equipment to be installed: main engines, auxiliary engines, fire pumps etc. The lay-out of the engine room may also influence the breadth.The minimum distance between the main engines and the rudder propellers follows from the maximum allowable angle of the cardan shafts (maximum 15 degrees) and the shape o f the aft ship sections. This distance also determines the minimum length of the compartment between the engine room and the thruster compartment, It is mostly used for tanks and stores. The remaining parts of the tug's length are destined for fore and aft peaks and a compartment forward of the engine room with tanks and possibly some accommodation space. Tank capacity requirements and proper trimming possibilities in different loading conditions determine the length of these compartments.Breadth and depth have to be sufficient to provide good stability, the freeboard large enough to give a dry working deck.The block coefficient is not very critical in harbour tug design. Care should be taken, however, to ensure a good flow o f water to the propellers and to avoid sharp shoulders in the fore ship.

The engineering phaseIn the last phase o f the process, the design as prepared in the second phase, is worked out in all detail. This is not much different from normal engineering practice. However, some specific aspects for harbour tugs are mentioned here,A robust construction is necessary, which makes it desirable e.g. to choose the shell thickness well in excess o f rules’ requirements. The exterior construction should be as flush as possible to prevent the tow line from getting fouled. A flush construction also reduces the amount o f maintenance work.

The towing arrangements have to be carefully detailed to obtain optimum efficiency and the highest degree of safety.Much attention has to be paid to maintainability in the engine room: good acces- sability of components and ease o f removal are important aspects. Good maintainability is especially important when the tugs have to operate in remote areas where re pair facilities are not near at hand.The lay-out of the bridge and the controls is another aspect which merits full a tten tion, as it influences to a great extent the operational qualities of the tug.An unobstructed view from the wheelhouse is a further aspect which merits a ttention. For this reason, and also because it is less noisy and saves space, Wijsmuller Engineering prefer to dispense with funnels and to lead the engines' combustion gases aft, below decks, and to exhaust them near the stern, via a water lock. Yet, some fleet- owners still require funnels.Wijsmuller Engineering can take care o f all the three phases of the design process, and also of the economic evaluation o f p ro jects, the building supervision and the training of crews.

Future developmentsAs the size of merchant ships is not likely to any increase further, no spectacular in creases in bollard pull are to be expected. A bollard pull of 60 tons per tug seems to be the maximum, also because w ith larger bollard pulls the dimensions of the tow ing gear w ill become too large fo r easy and safe handling.Smaller crews are to be expected, both on the tugs and aboard the ships they are assisting. This w ill have consequences fo r the hook-up procedures and for the choice o f equipment. A suction cup system, d e veloped in Japan, has not yet found much acceptance.Remote control of the tug by the p ilo t aboard the tow o r even from the shore may be expected in the not too distant fu ture.

R EC EN T PROJECTSThe first rudder propeller harbour tugs designed by Wijsmuller Engineering were the four ships of the Provincie-class, commissioned in 1981 fo r use in the Amster- dam-IJmuiden area. Another four ships to the same design were completed in 1982(3).Since then the following projects have been handled by Wijsmuller Engineering:- Kari and tw o sisterships for Finland,

completed in 1981 ;- Ultramar X for Chile, 1983;- Dux and Pax fo r Norway, 1985;- Brightwell fo r the United Kingdom (4),

1986;- Maria Isabel and Maria Louisa for Pana

ma, 1987;- Velox and three sisterships for Norway,

1988;- tw o tugs fo r the Orkney Islands, under

construction;- five terminal tugs for Mexico, tenders

requested.Three o f the projects w ill be described in some detail, the Kari because of her ice breaking capabilities, which necessitated some special design features, as well as the tw o designs fo r Norway. Although the designs fo r Norway were developed for the same owners, they are quite different, which illustrates the influence of the different conditions in the respective ports.

KARIThe Kari and her sisterships, Aulis and Esko, were built by Hollming Oy for the state oil company Neste Oy. They operate mostly in the port of the Skoldvik refinery, but they are also suitable fo r towing duties in coastal and inland waters. O ther duties include fire fighting and supplying fresh wate r to ships in port.

Their main particulars are:Length o.a. 29.80 miLength c.w.l. 28.90 miBreadth o.a. 10.40 miBreadth mid 10.00 mi


Foto: Henk Koning

Depth mid Draught mid

5.00 m; 4.20 m.

The hull has been specially designed for icebreaking, both as regards the hull form and the very heavy construction, which is in accordance with Finnish ice class I A.As icebreaking is a noisy business, which also causes much vibration, the complete deckhouse is mounted on rubber fittings. Propulsion is by tw o Wartsila Vasa diesel engines, type 8R22C, each developing 1270 kW at 1200 rpm. They each drive a rudder propeller of Hoilming make, type Aquamaster US ! 600, giving a bollard pull o f 40 tons; the free running speed is 12 knots.There are tw o 95 kVA diesel generator sets.Towing gear includes a combined towing winch/anchor winch forward, which in combination w ith a heavy fender makes the ships most suitable fo r push-pull operations. For other towing duties there is a 50 tons towing hook, just aft of the deckhouse.For fire fighting a fire pump of 360 ts/hr and a monitor on top of the signal mast are available, as well as a spray system fo r protection of the tug itself. The pump is driven by the PS main engine through a PTO, gear and clutch.The tank capacity fo r supplying FW to other ships is 100 t. A 50 cu.m/h transfer pump is installed in the engine room. Accommodation has been provided for a crew o f six.

D U XThe Dux and her sistership Pax were built by Skaalurens Skibsbyggeri AS, Rosendal, Norway, fo r Johannes Ostensjo dy of Haugesund, Norway. They have been designed to assist gas tankers of 30,000 to40,000 tdw, when berthing and unberthing at Karsto gas terminal In Norway and for fire fighting. It was an owners’ requirement that they are o f the tractor type. Additional activities include:- escort services;— coastal and sea towage;— pollution combat and control;- salvage work.

The main particulars are:Length o.a. 29.70 m;Length b.p. 28.00 m;Breadth mid 9.00 m;Depth mid 4.50 m;Draught 5.80 m.

Propulsion is by tw o Bergen diesel engines, type KRMB6, each developing I 100 kW at 900 rpm. They each drive a Liaaen Compass thruster, type TCN 83/56-230, w ith a CP propeller operating in a nozzle at 233 rpm. The bollard pull is 42 tons, the free running speed 12 knots. There are tw o 160 kVA diesel generator sets.

Towing gear includes a hydraulically driven towing winch, type KARM, and a 4 5 1 SWL towing hook of Mampaey make. The winch has one double drum, w ith 600 m of 40 mm wire fo r sea towage and 120 m of 40 mm wire fo r harbour towage. The pull is 70 tons, the brake load 100 tons.

For fire fighting purposes tw o pumps of 390 cu.m/hr at 15 bar each are available. One monitor, w ith a capacity o f 5000 !i- ters/min., is mounted on top of the signal mast, 2 1 m above sealevel, and is remotely controlled. Two additional monitors, on top of the wheelhouse, have a capacity of 2500 liters/min. each and are locally controlled. A spray system is fitted for protection of the tug itself.For escort duties and for coastal and sea voyages, extensive navigation and communication equipment has been provided, including:- JRCJMA 3410 colour radar;- JRCJMA Mil 3 cm radar;- Shipmate RS 4000 navigator;- Robertson RPG 90 gyro;

V E L O XThe Velox and her sisterships Tenax, Au- dax and Vivax were built by Batservice Verft AS, Mandal, Norway, for Johannes Ostensjo dy.They have been designed to handle tankers up to 300.000 tdw under all weather conditions at the Sture and Mongstad term inals in Norway (near Bergen) and for fire fighting and oil pollution combat and contro l. They are also equipped for making coastal voyages and fo r rescue operations at sea. Further duties are supplying water and lubricating oil as well as electric and hydraulic power and compressed air to vessels at the terminal, transport o f equipment and anchor handling for buoys and other navigational aids.

Their main particulars are:Length o.a. 33.34 m;Length d.w.l. 30.40 m;Breadth mid 10.00 m;Depth mid 5.60 m;Design draught mid 4.25 m;Scantling draught max. 5.00 m.

- Robertson AP 9 GA autopilot;- JRC JEFFE 570S echo sounder;- JRC JLN 203 Doppler log;- Skanti TRP 6000 radio telephone;- tw o Sailor RT l46VHF-sets;- Panasonic NMT mobile telephone;- Panasonic UF-400 telefax.

Detergents are available for pollution combat and control.Two transportable submersible pumps are carried for salvage work.Accommodation is provided for a crew of six. including tw o officers. A six-man inflatable life raft is fitted on either side o f the wheelhouse. In addition a MOBoat is available, which is handled by a deck crane of1.5 tons at 7 m outreach.

As the terminals are exposed and adverse weather conditions are definetely not uncommon in the area, a long forecastle has been incorporated in the design to improve seakeeping qualities and to give some protection to the crew working on the aft deck.The design has been extensively tank tested at Marintek, Trondheim, Norway. The results o f the tests are discussed in (5). Propulsion is by tw o MaK diesel engines, type 8M332, each developing 1600 kW at 900 rpm. They each drive a Liaaen, type 92/68-250, Compass thruster, w ith a 2.5 m diameter CP propeller in a nozzle. The bollard pull is 58 tons, the free running speed 13.5 knots. There are tw o 200 kVA diesel generator sets.


Foto: Henk Koning

The vessels are suitable for all modes of operation. Towing gear includes towing winches forward and just aft of midships, at 60 t SWL Mampaey towing hook and heavy rubber fenders all around. The winches are of Karmoy make and have a maximum pull of 45 t at 16,6 m/min and 60 t at12.4 m/min respectively; holding power is 150 t. They are remotely controlled from the bridge.The tw o fire pumps, each with a capacity of 400 cu.m/h at 15 bar, are driven by the main engines. They supply water to three monitors and to a spray system for protection of the tug itself. One monitor, of 5000 l/min capacity, is located on top of the signal mast and has remote control;the other tw o monitors, 3000 l/min each, are located on top of the wheelhouse and are locally controlled. The foam tanks have a capacity o f 12 cu.m.The Velox and her sisters carry extensive equipment fo r combatting pollution. An inflatable oil boom is stored on a large reel, located at PS next to the midship towing winch. It is paid out via the stern roller and inflated by a separate compressor in the engine room.Detergent spray booms are fitted on either side of the deckhouse. The tank capacity fo r detergents is 2 cu.m. Skimmers are also at hand; they are handled by a deck crane with a SWL of 5 t at 10 m. The oil which is recovered is stored in wing tanks in the compartment directly aft of the engine room; the tank capacity is 66 cu.m. When the skimmers are not in use, they are stored in the rope store which is in the same compartment.

Navigation and communication equipment is in accordance with the requirements for coastal voyages and is similar to the equipment of the Dux although there are some changes in makes.For supplying FW and LO to other ships, the FW tank capacity is extra large, 47 cu.m, and separate LO cargo tanks o f 52 cu.m capacity have been provided. The transfer pumps are located in the engine room.Anchor handling equipment comprises the 10 0 1 SWL stern roller, tw o hydraulic to w ing pins and shark jaws.For transport duties the aft deck is kept flush, including the hatch to the rope store. In normal service the ships carry a crew of four who live on board. Accommodation has been provided for eight persons in tw o single and three double cabins.Life saving equipment includes tw o eight- man inflatable life rafts and a MOBoat.

C O N V E R S IO N SWijsmuller Engineering has also handled several projects for conversion of conventional tugs. In these cases a retractable rudder propeller has been installed in existing tugs to improve their manoeuvrability. An

increase in bollard pull is an additional advantage.The first project concerned some tugs of Goedkoop, one of the operating companies within the Wijsmuller group (6). Similar conversions have been engineered for the tugs Kemsing, of MessrsJ.P. Knight, and Bargarth, of Messrs Cory.

O th er W ijsm uller Engineering activitiesHarbour tugs are not the only type of vessel on which Wijsmuller Engineering has expertise. They are also specialized in large seagoing tugs, heavy lift vessels and offshore operations.Some special projects concern surface effect ships (SES), which are being developed in co-operation w ith the De Schelde yard in Flushing, and the ships which are needed fo r the Restore-project. The latter project, under the EEC ’Eureka’ programme, aims at the decontamination of polluted silt in harbour basins.Wijsmuller Engineering also developed several successful computer programmes fo r diverse applications in the maritime field.

References( I ) Ir. H. Bikker, ing. J. van Berkel. ir. F.

Kok, C.F.B. de With, Beheersing van het ontwerpen engineering proces, een rapport opgesteld in het kader van het FME-aanloopproject Produk- tiebeheersing; (Control of the design and engineering process, a report w ritten fo r the FME preliminary project on production control;) FME, 1983.

(2) Sven O. Aarts, The optimum tug fleet configuration; Proceedings of the International Tug Convention, 1985.

(3) Zeeland, short description of the tug Zeeland; Schip en Werf, 1982, nr 9, p. 144.

(4) Brightwell, data sheet on the tug Brightwell; Ship & Boat International, December 1986.

(5) Sven O. Aarts, Development and design of the Terminal class tug; Proceedings of the 10th International Tug Convention, 1988.

(6) Het verbeteren van de manoeuvreerbaarheid van conventionele sleepboten; (Improving the manoeuvrability of conventional tugs;) Schip en Werf, 1982, nr 24, p. 388.


LITERATURE

SW 89-07-0 /Contractors gear up for the 1990s. N orth Sea pipelay m arketMeans, E.Noroil (02305), 8903, 17/3 pg-17, nrpg-3, tab-2, ph-2, ENG Zeepipe, Miller, Nogat, Beryl - all of these signify major North Sea pipelay projects scheduled to startup over the next two years, while a myriad of additional smaller jobs will contribute further to the work load. A fter a lengthy period of low activity, the early nineties w ill present more projects and more kilometres of pipe than ever before. This fact has not gone unnoticed by oil companies, which are already scrambling to place awards before contractors’ capacities are spent. However, European Marine Contractors (EMC) argues that the existing pipelay fleet - o ffering improved capabilities, equipment and techniques - has ample capacity to handle this influx of projects. 0630905

SW89 07-02Planning for subsea production w ith jack-up wellsBilderbeek, B. H. van; Milne, I. F.Subsea, Intern. Conf. (78428), 8812,/5, pg-1, nrpg-18, gr-7, ENG The evolution of mudline suspension equipment for use w ith jack-up drilling procedures can be divided into tw o distinct phases. The first phase saw the introduction of mudline suspension hangers as a means to facilitate the mobile nature of jack-up rigs. Casing was suspended at the mudline; washout provisions ensured clean annuli. Jack-up rigs could, therefore, move readily from location to location, disconnecting casing strings at the mudline, not having to contend with cemented risers. Once moved off, however, the well had served its purpose and was extended. The second phase commenced when the notion surfaced that these exploratory wells could, possibly, be used in production applications. 06201 14

SW89 07-03Motions of floating offshore structures in m ulti-directional wavesMaeda, K ; Morooka, K; Kasahara,A; Kinoshita, T.Naval Arch, and Ocean Eng. (03342), 8 8 12 ,25 /1987, pg-1 15, nrpg-7, gr-7, tab-1, d rw -l, ENGDue to the lack of facilities, only few experimental works have been carried out in the field of motions of a floating body in multi-directional waves. Therefore, the

authors carried out experiments on motions of a floating body in two-directional waves (perpendicular to each other) in a model basin and they checked the linearity of superposition o f waves and motions of the floating body. From these investigations, the authors pointed out the limitation of linearity and the interesting phenomena of slow drift oscillation of a moored floating body in two-directional waves. They also developed the experimental technique for motions o f a floating body in multi-directional waves and derived the theoretical prediction method for these motions in multi-directional waves based on functional polynomial method. 0630219

SW89 07-04Some factors influencing the behaviour of embedded anchorsHesar, M. A.; Harvey, R. C.; Jamnejad, G.H. NE Coast Inst, o f Eng. & Shipb. Trans. (03350), 8903, 105/2, pg-41, nrpg-9, gr-5, drw-8, ENGThe requirement fo r fixed offshore facilities in the oceans which rely largely, fo r holding station, on anchoring systems has provided the catalyst fo r much research and development work undertaken to provide efficient and reliable anchorages. Embedded systems, that is fully buried systems, which develop restraint forces by means o f interaction with the sea-bed material, are very efficient compared w ith alternative anchoring systems and need to develop small movement only in order to mobilise restraint. This can be of importance for complex and expensive facilities or in areas where there is a congestion of facilities at the sea-bed level. 0630614

SW89-07-05Fatigue and corrosion fatigue on fla t specimens and tubular joints, Dutch resultsScholte, H. G.; Overbeeke, J. L.; Dijkstra,O. D.; Wildschut, H.; Noordhoek, C.St. Materiaal Onderzoek v.d. Zee (0 1945), 8904, 15/2, pg-5, nrpg-8, gr-10, tab-3, drw-3, ENGThe Dutch part o f the ECSC-Offshore Steels Research Programme is presented. The aim of the research was to provide the designer of offshore structures w ith relevant data about the (corrosion) fatigue behaviour of tubular joints. In addition to tests on tubular joints an extensive basic test programme on small scale specimens has been carried out. The programme has included a number of fatigue strength in-

Verzorgd door het MIC/CMO. Kopieën van de hier vermelde artikelen zijn tegen betaling verkrijgbaar bij.Nederlands Maritiem InformatieCentrum/CMOPostbus 218733001 AW RotterdamTel. 010-4130960, tst. 33

fluencing parameters, such as: environment, loading condition, weld defects, scale factors and plate thickness. Crack growth studies were carried out and fatigue analysis has been done, using linear elastic fracture mechanics. The results show that in seawater the lifetime under fatigue loading on the lower stress, high cycle range can be reduced to about I /3 of the lifetime in air. 0630217

SW89-07-06Corrosion preventing system of offshore structure by paint coatingArita, M.; Matsuoka, K.; Ohnaga, K.; Naito,S.; Shibata, T.Techno-Ocean symp. (78760), 8811,2, pg- 43, nrpg-7, gr-4, drw-4, ENG A corrosion preventing system of offshore steel structures is proposed. The system is composed of four parts. The first part is the selection of the optimum coating conditions based on a data base of coating film service life. The second is the determination of the minimum allowable radius of curvature of corners of structure's detail. The third is the estimation of residual service life of coating film based on a data base of coating film deterioration. And the last part is the feedback procedure of field and experimental data to the data bases. By adopting the proposed system, the corrosion preventing method by paint coating may be guaranteed to become reliable from the view point of service life estimation. 0630217

Rij bestelling van artikelen dient u het nummer van het abstract op te geven. Het eerste nummer tussen haakjes in de bronvermelding verwijst naar het door MIC/CMO gehanteerde publika- tie code systeem.De bibliotheek van het Nederlands Maritiem Informatie Centrum is geopend op werkdagen van 11.00 tot16.00 uur.Het adres is Blaak 16, Rotterdam.


SW89-07-07D Y P O S 625, th e new genera tion o f d ynam ic pos ition ing systemsAhvenjari, S.Techno-Ocean symp.(78760),881 I, Lpg- 455, nrpg-4, drw-2, ph-3, ENG DYPOS 625, the new dynamic positioning system of Hollming Ltd. Electronics, is designed for automatic positioning, automatic sailing and centralized manual steering of various vessels with the highest degree of reliability. Modularity is a characteristic feature of DYPOS 625. The system is built up o f several single-board microcomputers which communicate with each other via a high-speed serial bus. Special attention is paid to the maintainability and safe operation of the system. Hollming Ltd. Electronics has developed a special IOA (Intelligent Operator Aid) expert system to assist the operation and maintenance of DYPOS 625. The IOA expert system gives the operator useful advice in critical situations, makes the tuning of the system faste r and easier, simplifies the management of system documents and supports system diagnosing and trouble-shooting. 0 150523

SW89-07-08Hydrogen em b rittlem ent of high- strength alloys in m arine environmentsButler, R. E.Marine Engineering with Copper-Nickel (74955), 8804, pg-79, nrpg-6, tab-6, ENG Failures have been experienced in Monel alloy K-500 (UNS N05500) drill stem parts and collars coupled w ith carbon steel, and in cathodically protected Monel bolts. In both cases failure was attributed to hydrogen embrittlement. Measurements have been made under slow strain rate conditions, w ith applied negative potential, on several alternative materials. The results described in this paper indicate that several duplex steels, Monel alloy K- 500, and high strength B7 low alloy steels, all suffer loss of ductility, but that a high strength cupro-nickel, even in the cold drawn condition, is immune to this form of embrittlement. 0630211

SW89-07-09Use of copper-nickel alloy sheathing for corrosion and fouling protection of m arine structuresGilbert, P. T.Marine Engineering w ith Copper-Nickel (74955), 8804, pg-21, nrpg-21, gr-1 I , tab- 5, drw-4, ENGSteel offshore oil and gas platforms and related structures are subject to corrosion and marine fouling and possibly to corrosion fatigue cracking due to stresses arising from wind and wave action and temperature fluctuations. Corrosion of undersea parts can be prevented by cathodic protection, but this is not effective in tidal and splash zones. This report is a compilation

of the information available on the use of 90% copper, 10% nickel alloy (Alloy C70600) for the sheathing or cladding of marine structures as protection against corrosion and fouling. 0630514

SW89-07-I0Offshore gas liquefaction: technical and economical potentialOverli.J. M.; Steineke, F.Gastech (71350), 8810 1/20, pg-l, nrpg- 32, tab-2, drw-9, ENG According to Norwegian regulations the operator of an offshore field is not permitted to flare associated gas during oil production. This creates problems, as traditional field developments including gas pipeline transport onshore result in considerable investments. The field may become unprofitable w ith today's oil and gas prices. This makes offshore gas handling important. Offshore gas liquefaction may represent the only solution to the gas problem. Statoil has studied and developed an offshore gas production system which takes care of associated gas released during oil production. The concept which shows high flexibility, is named the LNG/LIN concept. 0620114

SW89-07-IIOffshore rig outlook may improve in 3-5 yearsWagner, R. D.Oil & Gasjrnl (02387), 8905, 87/18, nrpg- 4, gr-1, tab-4, ENGContinued weakness in oil and gas prices and depressed levels of capital expenditures by oil companies have kept any real trend from developing in the supply and demand fo r mobile offshore drilling rigs. In fact, some forecasters around 1983 who saw substantial market improvement by the middle of this decade may have missed the future by 8-10 years. However, an analysis of the current supply situation for offshore rigs and the implications fo r day- rates from the analysis will provide some perspective o f the future. 0620112

SW89-07-I2Structural responses and design waves of semisubmersiblesSuhara, T.; Yoshida, K.; Yoneya, T. jrn l Offshore Mechanics and Arctic Engineering (01432), 8902, I I I / I , pg-12, nrpg-10, gr-15, tab-3, drw-7, ENG This paper presents the results of comparative calculations on structural responses of a typical semisubmersible and the discussion on design waves for brace stresses. A typical semisubmersible of two-lo- werhull type is adopted as a full-scale model for the comparative calculations on three-dimensional motion and structural responses. Based on the comparative calculations by eight different computer programs, standard response functions are proposed as to axial and bending stresses

of major braces. Characteristics wave loading patterns, which correspond to design waves, are proposed based on the standard stress response functions. Also simplified equations o f wave forces on semisubmersibles, which are useful to consider design waves, are derived based on the assumptions of taking account of only hydrodynamic inertial forces. Based on these results, maximum brace stresses during a 100-yr return period are estimated using design wave method, and are compared w ith statistically estimated values by short-term and long-term predictions. As a result, it is found that design wave method has a tentative ground for practical design of semisubmersibles. 0630219

SW89-07-I3Subsea separation: an answer for small field developm entSonghurst, B. W.; Edwards, W. G.Subsea, Intern. Conf. (78428), 8812,/7, pg- I , nrpg-23, gr-1, drw-16, ph-4, ENG British Offshore Engineering Technology Ltd. have recently developed an economic method for the production of submarginal oil fields (less than 30mb recoverable reserves). Following feasibility studies and the development of the conceptual design a 5,000 b/d pilot unit was constructed to prove the concept and installed on Hamilton ’s Argyll Field in the N orth Sea during the late summer of 1988. This paper presents the concept, potential market, economics and provides an overview of the pilot unit. A comparison is also made with other production methods fo r submarginal fields. 0620114

SW89-07-I4Developments in the production equipm ent for the T ro ll Oseberg gas injection (T O G I) projectOpenshaw, M.; Hopson, B.Subsea, Intern. Conf. (78428), 8812,/2, pg- I , nrpg-35, drw -13. ph-15, ENG This paper discusses the equipment being supplied fo r the TOGI subsea station, at a water depth of 303 metres positioned 70 km w/nw of Bergen in the Norwegian Trench. The installation and maintenance requirements of the equipment, necessitated that it be designed as a tru ly diverless system, w ith R.O.V. assistance. A ll active components have a minimum working life of 18 years and are housed in modules which are retrievable by use of drill string techniques. The philosophy of using field proven technology was adopted wherever possible. New designs were derived only when environmental and functional conditions dictated, 0630300


Agenda

Offshore EuropeThe ninth Offshore Europe exhibition and conference will be held 5-8 September 1989 at the Aberdeen Exhibition & Conference Centre, Bridge of Don, Aberdeen, Scotland.Europe’s premier offshore and gas technology event is held under the patronage o f the United Kingdom Offshore Operator’s Association and the sponsorship of the Society of Petroleum Engineers w ith Region X being responsible for developing a high level conference programme. SPE — sponsors of the show since 1983 — have taken a partnership position in Offshore Europe.The closer links between Offshore Europe and the SPE have resulted in a particularly strong conference. Some 70 papers have been selected by the conference committee headed by Alan Ace, Chief Operating Executive, Britoil pic, from well over 300 abstracts. Sessions will deal w ith Drilling Operations, Production Technology, Well technolgy, R & D and Innovative Technology, Practical Reservoir Management, Inspection and Maintenance, Safety and Environmental Protection, Development of Smaller/Marginal Fields, Business Aspects/ Management, Gas Development.As in past years, Offshore Europe has attracted over 1000 exhibitors from 20+ countries. All exhibitors are being urged to use the exhibition as the launch pad for new company products o r services and to show new hardware.In 1987 Offshore Europe attracted over20,000 key personnel from 54 countries. Key visitor groups are those with purchasing power in oil and gas exploration and production companies worldwide: engineering firms, contractors and consultants; construction companies; service companies; drilling contractors; and equipment manufacturers.Offshore Europe is organised by Offshore Europe (Management) Ltd. - a company operated for the partners by Spearhead Exhibitions, creators of the exhibition which was first held in Aberdeen in 1973. Contact them at Rowe House, 55/59 Fife Road, Kingston upon Thames, Surrey KTI I TA, UK. Tel.: 0 1 -5495831 Telex: 928042

SPEARS G Fax: 01-5415657 w ith all queries.

ZeeschilderIn het Dordrechts Museum, gelegen in het centrum van de historische havenstad Dordrecht, w ordt van 18 augustus t/m 29 oktober de tentoonstelling ’Een onsterfelijk zeeschilder’ gehouden.Ongeveer 100 schilderijen en tekeningen, waarbij een aantal absolute topstukken, geven een overzicht van het werk van de zeeschilder J. C. Schotel die leefde van 1787 to t 1838. Deze talentvolle kunstenaar, die zijn leermeester Schouman verre overtrof, w ordt als de beste Nederlandse zeeschilder uit zijn tijd beschouwd.Behalve een uitstekend schilder was Schotel ook een groot kenner van de meest u iteenlopende scheepstypen; hij was zelf jarenlang in het bezit van een boeier en heeft vanuit dit vaartuig heel wat schetsen gemaakt. Tot zijn onderwerpen behoorden schepen in allerlei situaties: in stormweer of op een gladde zeespiegel, dramatische schipbreuken o f vaartuigen die behouden in de haven terugkeren. Ook stadsgezichten werden door hem op papier of doek gebracht.Tijdens zijn leven was Schotel al een beroemdheid. Hij verw ierf internationale bekendheid en schilderde voor de Russische keizer en de koning van Pruisen.Het bij de expositie verschijnende boek bevat veel biografisch nieuws over Schotel, o.a. over zijn reizen langs de Westeu- ropese kusten, zijn schildertechniek en zijn klantenkring. Het is voorzien van vele illustraties en in het museum voor ƒ 29,50 te koop. Het Dordrechts museum is geopend op dinsdag t/m zaterdag van 10.00-17.00 uur en op zondag van 13.00-17.00 uur. Informatie: Dordrechts Museum, Museumstraat 40, 3311 XP Dordrecht

Cursussen Inform aticaHet nieuwe Praktijk Diploma Informatica blijkt in de praktijk zeer waardevol te zijn. De gediplomeerde is op MB-niveau bekend met de mogelijkheden en toepassingen van computers en hun programma’s en weet die programma's ook te installeren en op details aan te passen aan de bedrijfssituatie. W ie het PDi heeft, benut computer en randapparatuur volledig en zo efficiënt mogelijk.Het PDI is een rijkserkende opleiding en bestaat uit twee delen, PDI-1 en PDI-2, Het diploma voor deel I omvat de cursus

sen Technische Middelen, Systemen en toepassingen en Basis PC-gebruik. Het is een stevig fundament voor de keuzecur- sussen van deel 2, Programmering, Bestandsbeheer, Decentraal computergebruik, en Automatisering en Techniek.De PDI-cursussen kunnen overdag en 's avonds worden gevolgd in de plaatsen A lmelo, Amsterdan, Arnhem, Eindhoven, Rotterdam, Utrecht, Zoetermeer en Zwolle. De docenten komen uit de praktijk van overheid en bedrijfsleven. De cursussen beginnen weer in september 1989 en op elk van de cursussen kan reeds nu worden ingetekend.De PDI-cursussen kunnen ook voor bedrijfsgroepen worden gegeven. In een vrijblijvend gesprek kunnen de specifieke voordelen worden besproken.Alle gegevens over de PDI-cursussen zijn te vinden in de nieuwe studiegids met meer dan 80 andere opleidingen, die op aanvraag w ord t toegezonden.Meer informatie:NTS van Diemenstraat 164, 1013 CN AmsterdamTelefoon (020) 204128.

Cursus Com m ercieel Technisch M edew erkerOm aan de toenemende vraag vanuit het bedrijfsleven naar commercieel technici te voldoen het Koninklijke PBNA de opleiding ’Commercieel Technisch Medewerker’ ontwikkeld.Een commercieel-technicus is een functionaris, die naast een technische opleiding beschikt over kennis van o.a. marketing, bedrijfsorganisatie en bedrijfseconomie. Daarnaast moet hij of zij communicatie- en taalvaardig zijn.De opleiding is bestemd voor technici op MBO- of HBO-niveau. In de cursus zijn de volgende leervakken opgenomen: verkooptechnieken, commerciële economie, bedrijfsadministratie, wetskennis en marketing. De mondelinge opleiding w ordt vanaf september gegeven in Rotterdam, Amsterdam, Utrecht, Enschede, Eindhoven, Arnhem en Leeuwarden. In 22 lesavonden komen alle praktische en theoretische onderwerpen aan de orde.Naast de mondelinge opleiding biedt PBNA ook de gelegenheid deze cursus schriftelijk te volgen. Bij een aanbevolen studietempo van 10 <i 12 uur per week duurt de cursus 10 maanden. Na afloop worden er twee mondelinge dagen georganiseerd in Utrecht, leder voor- en najaar w ordt voor deze opleiding het examen afgenomen. Informatie en aanmelding bij PBNA, Postbus 9053, 6800 GS Arnhem, tel. 085-575911.

PRADS’89PRADS’89 is a follow up of the symposia held in Tokyo (1977), Tokyo and Seoul ( 1983) and in Trondheim ( 1987) and is in- tended to provide broad presentation and

NIEUWSBERICHTEN


exchange of advanced methods and achievements in different aspects concerning the design and operational performance of ships, waterborne vehicles and ocean engineering structures. PRADS’89 will be held as a multi-disciplinary Symposium and will attract ship designers, shipbuilders, ship operators, designers and operators o f offshore structures, naval architects, marine engineers, hydrodynami- cists, computer and control engineers, technical experts and others w ith a common interest in the field of practical design of ships and waterborne mobile units.The general aim of this Symposium is to show the latest achievements and ideas, as well as some general directions and predictions fo r the developments in the next decade. Therefore, the motto of PRADS'89 is The Shipbuilding Industry on the Threshold of 2 1 st Century’.PRADS’89 will be held in Varna, Bulgaria from 23 to 28 October 1989. The city of Varna is situated on the Black Sea coast closely to the places where the first world civilization has been established about 8000 years ago, being now world-famous cultural, congress and scientific centre, magnificent sea resort with many places of interest and entertainment. The weather usually expected at the end of October is moderate and pleasant. Rainy days may occur. The Symposium sessions will take place at the Cherno More Hotel located at the central city pedestrean zone closely to the seaside park and main shopping areas. In case of any questions or need of any additional information please don’t hesitate to contact:PRADS’89 Organizing Committee Bulgarian Ship Hydrodynamics Centre 9000 Varna, BULGARIA Phones: 052-775180 and 052-775186 Telex: 77497 BSHC BG

U nderw ater engineeringSafety and efficiency in the underwater engineering industry will be under discussion at this year’s Subtech, the biennial subsea engineering conference at Aberdeen Exhibition and Conference Centre from 7 to 9 November. The three-day event is organised jointly by the Association of O ffshore Diving Contractors and the Society fo r Underwater Technology.Theme of the conference is Fitness for Purpose and after the opening speech by the chairman of Shell UK, Robert Reid, the morning o f the first day will be taken up w ith a workshop. The conference will late r discuss whether current certification procedures satisfy present safety requirements, whether personnel are trained to appropriate standards and whether the difficulties encountered in inspecting and maintaining subsea production systems, pipelines and flexible flowlines can be improved.

(Society fo r Underwater Technology, at the Memorial Building, 75 Mark Lane, London EC3R7ED)

Proeftochten

ms ’Lukas’Op zaterdag 29 april, Koninginnedag, werd onder de bij deze dag behorende stralende zon een nieuwe bitumentanker, de 'LUKAS’, door Niestern Sander bv Scheepsbouw en Reparatie aan haar opdrachtgever, Smid & Hollander te Hoogkerk, overgedragen.Twee dagen voor de overdracht werd op de Eems de technische proeftocht gehouden in aanwezigheid van de opdrachtgevers, het bouwtoezicht Sandfirden, Scheepvaartinspectie en Bureau Veritas. Tijdens de proeftocht werden alle voorgeschreven beproevingen en testen uitgevoerd en bleek het schip ruimschoots aan de gestelde eisen te voldoen. Het gemiddelde geluidsniveau in de accommodatie bleef ruim onder de door de wet toegelaten maximale niveaus.De ’LUKAS’ is een binnenvaarttanker, ty pe V, voor het vervoer van warme bitumen in de klasse K3, met een losse geïsoleerde ladingtank.

Het ontwerp werd volledig door de werf in nauwe samenwerking met opdrachtgevers, het bouwtoezicht en Conoship, verzorgd.De ’LUKAS’ is gebouwd onder toezicht van Bureau Veritas, klasse: 1 3/3 E + NI I tanker type V en Scheepvaart Inspectie vlg. eisen van het ADNR. Het bouwtoezicht werd verzorgd door Sandfirden te Haren.

De algemene gegevens van de 'LUKAS’ zijn:Lengte over alles: 74.80 mBreedte spt: 6.76 mBreedte over alles: 6.80 mHolte midscheeps: 4.20 mDiepgang ontwerp: 2.75 mKruiphoogte: 6.80 mLaadvermogen: 840 tonLadingtanks, 8 stuks, inhoud: 920 m3Brandstoftanks: 24.34 m 3Drinkwatertanks: 8.80 m3Ballasttanks: 25.40 m3Hoofdmotor: Cat 3508 DI-TA; n 1200 525kWSchroef: Ostermann 5 bl 1.52 m Boegschroef: Werkina SD 800 3 K 150 kW Boegschroefmotor: Valmet 612 DS 167 kWGeneratorsets: Valmet/Stamford 2 st 25 kWStuurmachine: vd Velden 2 DW K 6080/35 Roeren: vd Velden 2 st HD 160 Ladingpomp: Stork SRT 150 125 m3/h

Lens-ballastpompen: K & R SAE 2 108-18030 m3/hTO installatie: Konus 300 kW.

De belangrijkste andere leveranties werden verzorgd door:Bloksma: beunkoelers Bos bv Scheepselectro: elektrische installatieCapellen v: geluidsadviezen Cleton: isolaties Conoship: ontwerp Paul Dinges: ladingpompaandrijving Friesland Staal: staal Graaf de: schilderwerk Haan Gebr. de: sanitair Helder & May: zwevende vloeren Intra automation: niveaualarmeringen Keystone: appendages Machinefabriek Niestern: diverse installatiesMarine Equipment Holland: ankers Navco: navigatie apparatuur Niestern Sander: betimmering roef Niestern Sander: inbouw machinekamer Rek & Horsman: ankerlieren, kettingen Rubber design: elastische ondersteuningen Stork: ladingpomp Tinnemans: stuurhut bovenhelft Vries RJ de: inventaris

ElizabethSinds half mei 1989 heeft L. H. Visser & Zn. Towage and Marine Services uit Oude- schild (Texel) de beschikking gekregen over een multifunctioneel offshorevaar- tuig. Het betreft de voormalige Damen Dragon Fly, die inmiddels, geheel in de traditie van rederij Visser, is herdoopt in Elizabeth.De nieuwe Elizabeth is een zogeheten ’anchor-handling tug supply vessel’. D it houdt in, dat het vaartuig, naast het verslepen van schepen en booreilanden, ook ankerbe- handelings- en bevoorradingswerkzaam- heden kan verrichten. Voor d it laatste beschikt de Elizabeth over een groot, vrij werkdek.

De voortstuwing van de Elizabeth vindt plaats door twee hoofdmotoren van elk 1200 pk, die ieder een schroef in een straalbuis aandrijven. Bijzonder is, dat het schip ook over een een intrekbare, 1200 pk sterke Aquamaster-unit beschikt, die in het voorschip is gemonteerd. Indien nodig, kan men deze schroef laten zakken, waar

250 SenW 56STE |AARGANG NR 7

door de bollard puli van het vaartuig van 32 naar 48 ton kan worden opgevoerd. T ijdens werkzaamheden in ondiep water w ordt de boegschroef naar binnen getrokken. De afmetingen van de Elizabeth bedragen: lengte 40,80 meter, breedte 10,00 meter, holte 4,50 meter en diepgang 3,30 meter.Naast het uitvoeren van sleep- en off- shorewerkzaamheden, kan de nieuwe Elizabeth ook worden ingezet bij duiken bergingswerkzaamheden, alsmede bij werkzaamheden ten dienste van de baggerindustrie.Ondertussen heeft de Elizabeth haar eerste sleepreis uitgevoerd. Een 85 meter lang droogdok werd van Göteborg in Zweden naar Breskens versleept. En binnenkort zal het vaartuig een ander droogdok van Nederland naar Mauretanië slepen.De voormalige Damen Dragon Fly, die is overgenomen van Damen Marine Services, is het derde vaartuig, dat in de Visser-kleu- ren de naam Elizabeth draagt. Atlas Transport Services uit Amsterdam zal als agent optreden voor L. H. Visser & Zn. Towage and Marine Services.

’Hang Lian 702’Met enig Chinees ceremonieel is op 15 juni te water gelaten de emmermolen ’Hang Lian 702’. De 'Hang Lian 702’ is een zelfvarende emmermolen, die op de w erf van IHC Holland in Sliedrecht wordt gebouwd voor de Shanghai Dredging Corporation in de Volksrepubliek China.In het midden van 1988 werden in Beijing contracten getekend voor het ontwerp, de bouw en de levering door IHC Holland vanuit Nederland van twee baggerwerk- tuigen, bestemd voor de Volksrepubliek China. De eerste betreft de 3450 kW cutterzuiger WEI LONG, die inmiddels op transport is naar Guangzhou.De HANG LIAN 702 is een zelfvarende emmermolen met een emmerinhoud van 500 liter.De schroef w ordt tijdens vaarbedrijf aangedreven door de hoofddieselmotor van I 125 kW. Tijdens baggerbedrijf d rijft dezelfde motor de generator aan, die de stroom levert voor de elektromotoren van de emmerkettingaandrijving, lieren en andere hulpwerktuigen. Verder zijn twee hulpgeneratorsets geïnstalleerd, elk aan- eedreven door een dieselmotor van 90 kW.De maximale baggerdiepte van de HANG LIAN 702 bedraagt 20 meter. Aan boord w ordt een air-conditioned accommodatie ingericht voor een bemanning van 50 personen.De oplevering van de baggermolen vindt plaats in augustus 1989. De molen zal op eigen kracht naar Shanghai varen.

Hoofdgegevens Naam: HANG LIAN 702

Type: Zelfvarende emmermolen Bouwjaar: 1989Opdrachtgever: Shanghai Dredging Corp., PRCBouwwerf: IHC Holland Lengte o.a.: 80 m Lengte tussen 11: 67.90 m Breedte: 14 m Holte: 5.10 m Emmerinhoud: 500 I Max. baggerdiepte: 20 m Vermogen hoofdmotor: 1125 kW Hulpvermogen: 2x 90 kW Vermogen op emmerketting: 500 kW Vaarsnelheid: 9 knopen Accommodatie: 50 personen

De HANG LIAN 702 w ord t gebouwd overeenkomstig de reglementen van Bureau Veritas voor de klasse I 3/3 (E) + Emmermolen en overeenkomstig de reglementen en onder toezicht van het Chinese Register of Shipping ZC voor de klasse 4- ZCA (Dredger, within 20 nautical miles offshore).

Product Info

C IM -TE K Hydrosorb filterBij transportbedrijven en in de landbouw, de wegenbouw, de luchtvaart en de scheepvaart vorm t stilstand van en storing in motoren als gevolg van (condens)water in de brandstof een voortdurend terugkerend en kostbaar probleem. Berg-O-Too!b.v. in Deventer heeft nu een absoluut betrouwbaar middel om dure motoren te beschermen tegen zowel water als vuil- deeltjes: het CIM-TEK HYDROSORB BRANDSTOFFILTER.Het Cim-Tek Hydrosorb brandstoffilter bestaat uit een gietijzeren aansluitstuk, dat aan beide zijden is voorzien van een duimse aansluiting. Het bevat een gemakkelijk te verwisselen filterelement, bestaande uit een fiberglas filtermat, die is geïmpregneerd met een waterabsorberend poeder. D it poeder bezit een tweetal zeer bijzondere eigenschappen: in eerste instantie w ordt alle water geabsorbeerd terw ijl de

schone brandstof ongehinderd kan doorstromen. Echter, wanneer het filter verzadigd dreigt te raken met water, gaat het poeder over in een voor brandstof ondoorlaatbare vorm.De opnamecapaciteit van het Cim-Tek filte r is, afhankelijk van het gekozen type, 0,75 to t 2,80 liter water. Wanneer de maximale waterhoeveelheid is bereikt, slaat het filter direct dicht. Het is dan uitgesloten dat verontreinigde brandstof de motor bereikt, hetgeen een absolute beveiliging is van de motor.Bij temperaturen onder het vriespunt behoudt het Cim-Tek Hydrosorb brandstoffilter zijn werking to t minimaal 50 procent van zijn capaciteit. Wanneer de temperatuur boven de 0° Celsius uitkomt, krijgt het filter zijn volledige wateropnamecapa- citeit weer terug.

Informatie: Berg-O-Tool B.V., van Beek. Telefoon: 05700-20666 (toestel 32).

W aterje tPROMAC B.V. kan nu ook Waterjetinstal- laties leveren in de vermogensrange van 25 to t 850 kW per unit. De Castoldi Water- jets worden reeds meer dan 25 jaar we


reldwijd met succes toegepast in ’high- speecf’-, plezier-, beroeps- en overheids- vaartuigen.Doordat onder het vlak uitstekende delen ontbreken w ordt de W aterjet ook veelvuldig gebruikt als voortstuwer voor vaartuigen met beperkte diepgang. Ingebouwd in b.v. reddingsboten is de W aterjet een ’veilige’ aandrijving.Door een uitgekiende constructie en een weldoordachte keuze van de toegepaste materialen is de Castoldi W aterjet geschikt om ook onder zware bedrijfsomstandigheden optimaal te functioneren. Door een unieke en zeer effectieve behandeling krijgen de delen, die met het (zee)- water in aanraking komen, een zeer slijtvast en corrosie-bestendig oppervlak. Dooreen geïntegreerde reductiekast is de keuze van de aandrijfmotoren en de aan- drijftoerentalien zeer uitgebreid, terw ijl toch steeds het optimale toerental van de impelier verkregen wordt.De manoeuvreereigenschappen van de Castoldi W aterjet zijn, door het gebruik van een uniek dubbel roeren systeem, u itstekend te noemen.Door middel van een ingebouwde schakel- bare koppeling kan de W aterjet in- en uitgeschakeld worden. Informatie:PROMAC B.V. te Zaltbommel, telefoon 04180-1 3855, telefax 04180-12400.

DrukschakelaarGebaseerd op hun standaard piezo-resis- tieve sensor brengen STS te Sirnach in Zwitserland, als een van de eersten, een volledig elektronische drukschakelaar op de markt, welke naast twee instelbare grenscontacten bovendien van een analoge uitgang van 1-3,5 volt voorzien is. Hiermede is een in de praktijk uiterst vervelende eigenschap van mechanische druk- schakelaars ondervangen, namelijk het verloop van de ingestelde schakelpunten ten gevolge van temperatuur variaties en veroudering o f slijtage. Daar de elektronische schakelaar van STS, gebaseerd op half-ge- leider technologie, geen bewegende delen

bevat, w ordt hiervoor een nauwkeurigheid van het schakelpunt van +/-0,25% van het meetbereik gegarandeerd.Dc beide schakeluitgangen zijn opgebouwd als transistoruitgangen, waarbij door middel van LED’s op de achterzijde van de schakelaar de schakeltoestand aangegeven wordt.Bovendien zijn de beide schakeluitgangen galvanisch gescheiden van het analoge signaal door opto couplers, waardoor geen onderlinge beïnvloeding mogelijk is. De uitgangen kunnen zowel in rust- als ar- beidstroom principe geschakeld worden, waarbij de maximaal toelaatbare stroom 500 mA bedraagt.Hierboven treedt de maximale stroom beveiliging in werking, waardoor de uitgang geopend wordt. Onderbreking van de voedingsspanning is dan noodzakelijk om de schakelaar weer in de arbeidsstand te zetten.

Specificaties:Nauwkeurigheid: + / —0,25% FRO Temp. bereik: — 25-80üC max. 125°C. mogelijk Voedingsspanning: 9-30 VDC Stroomopname: ca. 10 mA Analoge uitgang: 1-3,5 VDC Max. schakelstroom: 500 mA Drukaansluiting: G 'A"Afmetingen: diameter 43 mm, lengte 70 mm, IP67Schakel hysterese: standaard 1%, andere waarden naar keuze Informatie: Doedijns Electronics BV. Postbus 10054, 3004 AB Rotterdam tel. 0 10-4379133 fax 0 10-4370271

Bewakingssysteem olielozingVolgens het internationale Marpol-ver- drag dienen tankers te zijn uitgerust met een controlesysteem, waarmee het oliegehalte w ordt bewaakt in het geloosde ballast- en tankreinigingswater. Bovendien is bepaald dat tankers met een draagvermogen boven 4.000 ton een automatische inrichting moeten hebben voor het stop

pen van het pompen wanneer te hoge oliegehalten worden geregistreerd.Jowa Cleantoil 8788 voldoet als eerste systeem aan de nieuwe eisen volgens IMO 586 (14). Het grootste verschil tussen de eerste en de tweede generatie is dat het oliegehalte ook in combinatie met andere verontreinigingen nauwkeuriger kan w orden geanalyseerd. Voor de reder biedt dit belangrijke voordelen. Het legen van ballasttanks moest vroeger vaak worden onderbroken, omdat de oude meetapparatuur reageerde op andere verontreinigingen, zoals modder van de bodem die vaak in de tanks terechtkomt bij het innemen van ballast.In tegenstelling to t andere systemen, is jo wa Cleantoil 8788 uitgerust met een gepatenteerde, automatische reiniging van de meetapparatuur, een zeer belangrijke feature, daar het met de hand reinigen een groot karwei is.In de praktijk komt de gebruiker vooral in aanraking met de computer op de brug of in de machinekamer. Met behulp van de computer w ordt het legen aan de hand van parameters aangaande de snelheid van het vaartuig, de pompstroming overboord en het geregistreerde oliegehalte gecontroleerd en gestuurd in overeenstemming met de bepalingen die van toepassing zijn. Datum, tijdstip, het oliegehalte in het water, de totaal weggepompte oliehoeveel- heid, enz., worden geregistreerd en gearchiveerd. De uitdraai van deze gegevens moet gedurende drie jaar aan boord van het vaartuig worden bewaard.Behalve voor tankers, kan de apparatuur

natuurlijk ook gebruikt worden voor het beheersen van het oliegehalte in het ruim- water van andere soorten vaartuigen. Andere mogelijke toepassingen worden gevonden in de offshore-industrie of in olieraffinaderijen voor het beheersen van het afvoerwater.

Informatie: Jowa AB, Neongatan 8S-43133 MOLNDAL, ZwedenTel: +4631879200, Fax: +4631273726

252 “ ______________________________________________________ SenW 56STE IAARGANG NR 7

VERENIGINGSNIEUWS

Personalia

Afdelingsbestuur RotterdamIn de Vergadering van het afdelingsbestuur 'Rotterdam’ op 18 mei j.l. hebben de volgende mutaties plaats gevonden:Ir. R, K. Hansen heeft de functie van vice- voorzitter op zich genomen; Ing. J. J. P. Boot is secretaris.Prof. Ir. S. Hengst blijft in het bestuur als gewoon lid.

Aanwezig van het Hoofdbestuur de heren; Prof. Ir. S. Hengst, voorzitter J. Burlage, secretaris en vert. van de afd. ’Zeeland’L. Lussenburg, vert. van de afd. ’G roningen’Ing. G. van Wijk, vert. van de afd. ’Rotterdam’Ing. H. D. v. d. W erf, vert. van de afd. ’Amsterdam’J. M. Veltman, algemeen secretaris (verslag)

Afwezig met kennisgeving;Ir. J. C. Tjebbes, vice-voorzitter Ing. J. van Dorp, penningmeester Ing. H. Bitter, lid

Volgens de presentielijst aanwezig: 79

A G E N D A :1. Opening.2. Notulen van de vergadering dd.

27 april 1988.3. Overzicht van het afgelopen vereni-

gingsjaar.4. Bespreking jaarstukken 1988.

Vaststellen van de bestemming van het saldo over 1988.

5. Décharge van het Hoofdbestuur.6. Aanwijzing accountants voor 1989.7. Aanvullende begroting 1989 en ont

werpbegroting 1990.8. Contributie.9. Programma van activiteiten voor het

seizoen 1989/1990.10. Rondvraag en sluiting.

ad. I.De voorzitter Prof. Ir. S. Hengst opent te11.15 uur de vergadering en heet de aanwezigen welkom. Hij deelt mede dat de nieuwe penningmeester Ing. J. van Dorp,

In memoriam

J. M. HoogeveenOp 15 mei 1989 overleed te Wassenaar de heerj. M. Hoogeveen op de leeftijd van8l- jaar. Hij was Manager Maintenance and Repairs, bij de Nederlandsche Pacific Tank- vaart Maatschappij te Den Haag en was 27 jaar lid van onze Vereniging.

wegens ziekte verhinderd is, en dat de vorige penningmeester buitenslands is. De aanwezige bestuursleden zullen echter zo goed mogelijk de financiële zaken behartigen.

ad. 2.De notulen van de vergadering van 27 april 1988 worden goedgekeurd en ongewijzigd vastgelegd.

ad. 3.Verslag van het 91-ste verenigingsjaar door de algemeen secretaris. Het jaar 1988 was voor onze vereniging een gedenkwaardig jaar. Op 10 mei vierden wij samen met de leden van ’William Froude’ een gezamenlijk jubileum; wij 90 jaar; zij hun 17e lustrum. Een jubileumsymposium van één dag met een aantal prominente sprekers over het onderwerp: ’Innoveren of afmaken’ vormde de hoofd van de dag met als afsluiting een feestelijk aangeklede borrel in bakermat van ’William Froude’, de TU Delft.Onze afdeling ’Groningen’ vierde zijn zesde lustrum samen met de leden uit de andere afdelingen en hun partners tijdens een feestelijk jaardiner in ’Princenhof te Eer- newoude op 16 april.Verder werd het normale jaarlijkse programma in de vier afdelingen afgewerkt:3 nieuwjaarsrecepties en een 30 tal lezingen, die over het algemeen genomen goed werden bezocht.Het ledental liep enigszins terug en bedroeg per 31 december van het vorig jaar 2425; doch dit geringe verlies zal ruimschoots worden gecompenseerd door een aantal nieuwe leden afkomstig u it de nauwere samenwerking met de afdeling Maritieme Techniek van het Klvl. Deze samenwerking kreeg meer gestalte door een ge

zamenlijk lidmaatschap van de leden van beide verenigingen, hetgeen einde 1988 werd bereikt.Op personeelsgebied vonden ook veranderingen plaats; een nieuwe secretaresse, mevrouw Van Driel, nam de plaats in van mevrouw Zanen; terw ijl een nieuwe algemeen secretaris zijn intrede deed.O ok op materieel gebied waren er de nodige veranderingen. Het algemeen secretariaat dat sedert 1978 aan de Heemraads- singel 193, was gevestigd, verhuisde medio november naar Mathenesserlaan 185, eveneens op de begane grond van een gerenoveerd herenhuis, in de statutaire vestigingsplaats van onze vereniging. Rotterdam.Ook voor wat betreft 'Schip & W erf, het officiële orgaan van onze vereniging, vonden de nodige veranderingen plaats. Een nieuwe redacteur Dr. Ir. P. van Oossanen nam de plaats in van Ir. J. N. Joustra, die wegens zijn vele verdiensten to t erelid werd benoemd. Met de komst van de nieuwe redacteur was ook het MARIN weer in de redactie vertegenwoordigd, waardoor de wetenschappelijke inhoud van ’Schip & W e rf voor de komende jaren is verzekerd.Een toekomst die werd bedreigd door de in onze ogen, onverantwoorde afslanking van de afdeling Maritieme Techniek van de TU Delft, die werd samengevoegd met de afdeling Werktuigbouwkunde, hetgeen gepaard ging met verliezen van een aantal leerstoelen op maritiem gebied. Onze vereniging heeft zich samen met andere in het afgelopen jaar ingezet voor het behoud van deze, voor ons land zo belangrijke, tak van de wetenschap, doch helaas kon de bezuinigingsdrift m.b.t. de afdeling Maritieme Techniek nauwelijks worden ingedamd, Teneinde ons in te zetten voor de verbreiding van onze nationale kennis op maritiem-technisch gebied werd besloten om meer Engelstalige artikelen in 'Schip & W e rf op te nemen en werd subtitel ’Marine and Offshore Technology’ aan onze voorpagina toegevoegd, die tegelijkertijd een kleurige aanzien kreeg. Helaas, liep door een zwalkend beleid van de Uitgever het aantal advertentie pagina's opnieuw terug, zodat ook de revenuen hiervan voor onze vereniging aanzienlijk beneden de begroting bleven. D it ondanks de pogingen, die door de redactie werden aangewend om de kwantiteit en de kwaliteit van de inhoud te vergroten, om zodoende ook het blad voor adverteerders aantrekkelijker te maken. Ook ’Schip & W e rf ontkomt dus niet aan de bezuinigingen en verschijnt sedert I januari van dit jaar 12 maal per jaar, zij het met een ruimere inhoud van minimaal 32 pagina's per nummer. Gehoopt wordt d it met de opleving die eind 1988 in onze maritieme industrie plaatsvond ook het aantal advertenties in ’Schip & W erf' weer zal toenemen. Dit, mede de wellicht in de naaste toekomst te

N O T U L E N V A N DE ALG EM ENE LED EN VER G A DER IN G V A N DE N ED ER LA N D SE V E R E N IG IN G V A N T E C H N IC I OP SC H EEPVA A R TG EB IED , G E H O U D E N O P 26 APRIL 1989 IN H E T 'S C H ELD EK W A R TIER ’ TE VLISSIN G EN


realiseren fusie van maritieme bladen in Nederland. D it alles in het kader van de nauwere samenwerking tussen de maritieme verenigingen in Nederland.In het afgelopen jaar was onze vereniging vertegenwoordigd op twee internationale congressen namelijk het onder auspiciën van de Verenigde Naties georganiseerd congres 'Shipbuilding 2000' in Gdansk en op de 'West European Marine Technology' (WEMT) conference 'Advances in Ship Operations’ in Triest.Gedurende het jaar 1988 werden weer een twaalftal prijsuitreikingen verricht door verschillende bestuursleden bij de Maritieme Opleidingen in het gehele land. ad. 4.De voorzitter houdt een korte inleiding op de financiële jaarstukken over 1988. Hij verzoekt de leden om commentaar zodat hierop gereageerd kan worden. De heer Ir. J. N. Joustra neemt het woord met een aantal opmerkingen naar aanleiding van de jaarstukken. Hij deelt mede dat hij niet verwacht dat al zijn opmerkingen te r vergadering kunnen worden beantwoord. Daarom heeft hij ze op schrift gesteld, met de bedoeling dat ze later kunnen worden beantwoord. Op een enkel onderwerp w ordt ingegaan. Een afschrift van de opmerkingen van Ir. Joustra is bij de officiële notulen gevoegd. Er w ordt besloten alle opmerkingen integraal op een later tijdstip te beantwoorden, ad. 5.Er w ordt besloten het Hoofdbestuur décharge te verlenen voor het gevoerde financiële beleid in het afgelopen verenigingsjaar. ad. 6.Besloten w ordt om 'Moret & Limperg' wederom aan te wijzen als accountants voor 1989. Omdat de financiële administratie al grotendeels is geautomatiseerd, zal bezien worden of de accountants minder mankracht kunnen inzetten om de kosten van het onderzoek te drukken, ad. 7.Als onderdeel van de opmerkingen van de heer Joustra werd voorgesteld de uitgetrokken bedragen op de begrotingen van de afdelingen te verlagen, teneinde de uitgaven van de vereniging te verminderen. De heer Den Arend was het met d it voorstel niet eens. Hij betoogde dat in de eerste plaats deze begroting in de afdelings- vergaderingen in overleg met het Hoofdbestuur reeds waren vastgesteld en dat ten tweede de bedragen al reeds naar beneden waren bijgesteld. Een aantal leden was het met hem eens, waarna op voorstel van de voorzitter besloten werd niet meer aan deze bedragen te tornen.Ten aanzien van ’Schip & W e rf lichtte de voorzitter toe dat de opbrengsten voor de vereniging in 1989 even hoog gesteld zijn als die over 1988. Op de directe kosten zal aanzienlijk worden bespaard door minder extrapagina's te kopen en de redactiekos

ten te verminderen.Voor het jaardiner is wederom niets uitgetrokken op de begroting. Het Hoofdbestuur handhaaft zijn stelling dat van de hoge kosten te weinig leden profiteren. Initiatieven voor een kosten neutrale organisatie worden verwelkomt.De aanvullende begroting 1988 en de begroting voor 1989 worden hierna aangenomen, ad. 8.Het voorstel de contributie voor gewone leden met ingang van 1990 met ƒ 5 - te verhogen w ordt aangenomen. Als argument hiervoor geldt in de eerste plaats dat de opbrengst van het vermogen zal verminderen omdat hoogrentende obligaties uitloten en de rente thans lager is, en tweede is het saldo negatief, te r compensatie van het verlies is het beter nu de contributie alvast met een laag bedrag te verhogen. Het Hoofdbestuur stelde tevens voor de minimum bijdrage van de begunstigers te verhogen van ƒ 100,- to t ƒ 150,-. Als voornaamste argument geldt dat behoudens stemrecht, alle rechten per donateur gelden voor twee personen uit de directie. De vergadering besloot aldus, ad. 9.Ten aanzien van het programma van activiteiten voor het seizoen 1989/1990 deelt de algemeen secretaris mede, dat de verhuizing van het algemeen secretariaat het geheel is voltooid en dat hard gewerkt w ordt aan het automatiseren van de ledenen andere administraties. Bovendien zal in de zomer van 1989 een enquêteformulier worden gezonden naar alle leden met als belangrijkste doelen een controle van alle nodige gegevens en een belangen- en interesse registratie.De gesprekken met andere organisaties om te komen to t samenwerking gaan onverminderd door. De andere deelnemende verenigingen zijn:Klvl/MarTec, Onze Vloot, Vereniging Nationaal Instituut voor Scheepvaart en Scheepsbouw, de Stichting Algemene Maritieme Voorlichting, de Nederlandsche Vereniging van Kapiteins te r Koopvaardij, de Stichting De Zee, de Koninklijke Vereniging van Marine Officieren en de NVTS. De taken die in gezamenlijk verband kunnen worden uitgevoerd zijn:Coördinatie en/of samenvoeging van publicaties en gezamenlijke PR, organiseren symposia, ed, maritieme beroepsvoorlichting, excursies en stages en informatie verkregen voor parlement en regering.De voorzitter verzocht de vergadering om toestemming om in deze zin de gesprekken voort te zetten. De heer Stapel merkte op dat er de laatste tijd op allerlei gebied gereorganiseerd w ordt en stelde voor om niet meer dan eens in de 5 jaar te fuseren. De voorzitter merkte op dat er geen veranderingen plaatsvinden; er w ordt alleen samengewerkt. De heer Den Arend stelde voor om de resultaten van de

gesprekken in 'Schip & W e rf te rapporteren. Men ging vervolgens akkoord met het voeren van de gesprekken met andere verenigingen om to t een soort samenwerking te komen.De algemeen secretaris belichtte vervolgens de toekomstplannen voor 'Schip & W e rf die reeds gedeeltelijk in uitvoering zijn. Het blad heeft een ander uiterlijk en is maandblad geworden; met ingang van 1989 verschijnen er 6 themanummers. Ook in 1990 zijn wederom themanummers gepland. In samenwerking met de Uitgever worden 'Mailings' uitgevoerd naar het buitenland om het blad daar meer bekendheid te geven. Samenwerking met andere bladen zou zeer positieverbete- rend kunnen werken. De voorzitter stelt voor goed te keuren dat gesprekken hierover voortgezet worden met de volgende voorwaarden:'Schip & W e rf blijft een maritiem-technisch vakblad, het niveau moet worden gehandhaafd, verenigingsnieuws moet blijven, het eigendom van het blad blijft bij NVTS en Engelse artikelen blijven erin naast Nederlandse.Andere activiteiten:Het lezingenprogramma is bijna gereed; op 16 november 1989 organiseert de NVTS wederom de Maritieme ontmoetingsdag - er komt zo mogelijk ook een stand op de Europoort tentoonstelling. Op 23 maart 1990 organiseert de vereniging samen met DGSM en CMO een symposium over de veiligheid van Ro-Ro schepen in de Aula van de TU Delft.Het Hoofdbestuur verzoekt de leden om uit het vermogen een bedrag van ƒ 11.500,- te mogen gebruiken voor de uitreiking van prijzen voor de beste afstudeerverslagen uit de maritiem technische opleidingen. Een voorstel to t verdeling van de prijzen is als bijlage III van deze notulen opgenomen. Het voorstel w ordt door de vergadering aangenomen, ad. 10.a) Bij de rondvraag deelt de heer Den Arend mede dat de afdeling 'Amsterdam’ dit jaar 65 jaar bestaat. Hij stelt zich voor om als alternatief voor het jaardiner in de laatste week van september gedurende de middag en een deel van de avond een feest inclusief diner te organiseren waarvoor gestreefd wordt, de kosten te beperken to t ƒ 50,- per persoon. Het zal niet de allure hebben van een origineel jaardiner, maar een redelijke vervanging zijn.b) De heer Ir. O. R. Metzlar bedankt namens de vergadering het Hoofdbestuur en het algemeen secretariaat voor het werk van afgelopen jaar.c) De voorzitter bedankt de Koninklijke Maatschappij 'De Schelde' voor de gastvrijheid.Niets meer aan de orde zijnde w ordt de vergadering ten 12.50 uur gesloten.


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