Nautical Term en Logy

8/3/2019 Nautical Term en Logy

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Back to Nautical Ship Form Stresses Hull Structure Bow & Stern Fittings

Load Lines Rudder & Propeller

Ship ConstructionShip Dimensions and Form

General Cargo Vessel

These types of ships in general are built with longitudinal framing at the decks and in the double bottoms. Transverse framing is at the

sides.

Profile

The transverse strength is given by fitting transverses at the deck and plate floors are fitted in the double bottoms.

Longitudinal framing is not usual in general cargo vessels due to the high broken stowage involved. Also deep transverses then have

to be fitted about 3.7 metres to give the ship transverse strength.
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Bilge wells are fitted with a cubic capacity of 0.17 cbm. Nowadays ceiling on top of tank tops are generally not fitted as such the

plating is increased by 2mm. However where ceiling is fitted they should be removable in sections. The ceiling where fitted should

have a clear space for drainage at least of 12.5mm.

Cargo battens are fitted to the sides and to the turn of the bilges size of 50mm thick and spacing between rows of 230mm.

Midship


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Shown above is a centre line bulkhead in the lower hold and in the tween deck. This extends from the transverse watertight bulkhead

to the hatch coamings.

Tankers

These ships may have two or more longitudinal bulkheads today with double hull concept at least 3 but normally 4.

The bottom and deck are also framed longitudinally and so are the sides and the sides of the longitudinal bulkheads.

The length of a tank is not to exceed 0.2L. As the size of the tanker grows transverse wash bulkhead are fitted at about mid length of

the tank. These are for size of tanks over 0.1L or 15m whichever is more.

Centre line was bulk heads are fitted where the breadth exceeds the dimensions as laid out in the Rules for different size of tanks.

Cofferdams are provided both forward of the oil carrying space as well as in from of the ER bulkhead. Generally the pumproom is

located within the cofferdam aft. Some ships have a forward pump room located in the forward cofferdam.

The cofferdams are to be at least 760mm in length

Some smaller ships have a combined transverse and longitudinal framing system.

In lieu of bulwarks these ships are to have open rails on deck.

Cargo tanks are tested by a head of water in the cargo tank 2.45m above the highest point of the tank.

Generally a system of staggered test is undertaken. Alternate tanks are filled and the empty tanks is inspected. Once all the empty

tanks are inspected, the filled tanks are empties and the reverse tanks are filled and the other alternates inspected.

Inspecting of the tank welding are done by rafting within a tank.

Profile


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Plan

Midship


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Bulk Carriers:

These ships are characterised by their ability to carry cargo in bulk. If carrying grain and other lighter cargo all the holds are filled.

However if heavy cargo such as iron ore is carried then alternate holds are filled and to the designed loads only.

Profile


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The vessel may be constructed on the combined system, longitudinal framing together with transverse framing which are fitted at the

sides. The longitudinal framing is fitted in the double bottoms, the deck and the bottoms of the wing tanks.

The wing tanks may be utilised to carry cargo as well as remain empty. They carry ballast water during the ballast passage.

Transverse webs are fitted at in the wing tanks at intervals as laid out in the Rules. And side stringers are fitted at about 1/3

rd

and 2/3

rd

the depth of the tanks.

Plan

Midship


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Profile

On the top the hatch covers are mainly the side rolling Macgregor type.

The hatch breadth is usually about 50% of the breadth of the beam. The main disadvantage of this type of ship is the stability since

they are not built with a longitudinal partition in the centre the free surface effect is enormous and this necessitates overall loadingcomplexities.

Plan

Together with this is the sloshing effect which tend to damage the fitting inside.

The stability book would give the loading levels as well as the loading stability requirements as per the Rules.


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Midship

Container:

Longitudinal framing is used throughout the main body length of the ship. Transverse framing is used on the fore part and the after

part.

Profile


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The ships are built having a cellular construction at the sides. Strong longitudinal box girders are formed port and starboard by the

upper deck the second deck top of the shell plating and top of the longitudinal bulkhead. The upper deck and the sheer strake form

the box girder. These girders also provide stiffness against racking stresses and used as water ballast tank spaces.

Midship


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A form of bulkhead is fitted at intervals, centre to centre with water tight bulkheads being fitted as required by the Rules. The

bulkhead gives support to the double bottom structure.


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The container guides consist of angle bars about 150mm x 150mm x 14mm thick connected to vertical webs and adjoining structure

spaced 2.6m apart. The bottom of the guides is bolted to brackets welded to the tank top and beams. The brackets are welded to

doubling plates, which are welded to the tank top.

Ro Ro

Roll on Roll off ships have generally two ramps at either end of the ship to facilitate the loading of vehicles.

The main characteristic of these types of ships is the clear decks un interrupted by transverse bulkheads. Deck heights are sufficient to

accommodate the various types of vehicles carried.

Profile

The lower decks may be used for carriage of cars while the upper may be used for the carriage of bigger vehicles.

Transverse strength is maintained by fitting deep closely spaced web frames in conjunction with deep beams. These are usually fitted

every 4th frame and about 3 m apart.

The lower decks which are divided by watertight bulkheads have hydraulically operated sliding bulkhead doors which are opened

while working cargo in port.


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The deck thickness is increased to take the concentrated loads; a reduction in the spacing of the longitudinals with an increase in size.

A centre line row of pillars is fitted.

Ramps are fitted at the bow and at the stern to facilitate the loading and discharging of vehicles. The separate decks are reached by

fixed and sometimes hydraulically operated foldable operated ramps.

A service car is provided within the ship to transfer the lashing gear to the different decks.


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Midship

The stern ramps are generally set at an angle to the ships centre line to ensure that the ship can work cargo in any berth.


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Passenger:

The basic construction of these vessels follows the dry cargo vessel in their detail, a large number of decks being fitted.

Profile

Each passenger ship is differently built with the naval architects and the classification societies agreeing on the various additions to the

various pillars and bulkheads.

However the basic rule and the provisions of SOLAS, MARPOL are complied with.

Midship


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Midship in way of ER


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Definitions

Camber

The purpose of rounding the beam is to ensure a good drainage of the water and also to strengthen the upper deck and the upper flange

of the ship girder against longitudinal bending stresses- especially the compression stresses.

Rise Of Floor


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This is the distance from the line of floor to the horizontal, measured at the ship side. Purpose basically is to allow drainage of the

double bottom water/ oil to the centre line suctions.

Tumblehome


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This is the inward slope of the side plating from the water line to the upper deck today ships generally do not have a tumblehome.

Flare

This is the curvature of the side plating at the forward and gives additional buoyancy and thus helps to prevent the bows from diving

too deeply into the water when pitching.

The anchors are also clear when lowered from the flare of a ship.


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Sheer

This is the rise of ships deck fore and aft. This again adds buoyancy to the ends where it is needed during pitching. For calculating the

freeboard a correction is applied for the sheer. In modern ship the after sheer has been greatly reduced.


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Rake

This is the slope, which the forward end has with between the bottom plating and the upper deck. The length between perpendiculars

and the length overall difference is mostly due to the rake forward. It helps to cut the water and thus adds to the ships form.

Parallel Middle Body

This is the part of the main body of the ship and it is a box like structure enabling maximum cargo carrying capacity. It also helps in

the pushing when tugs are used to assist the vessel in berthing. Cargo stowage is also greatly facilitated.

Entrance

This part is the fore end of the ship and helps give the box like mid length a ship shaped structure.

Run


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The after part similarly to the fore part entrance helps in giving the box like mid length a ship shaped structure and thus the handling

of the vessel is enhanced.

Length means 96 per cent of the total length on a waterline at 85 per cent of the least moulded depth measured from the top of the

keel, or the length from the fore side of the stem to the axis of the rudder stock on that waterline, if that be greater. In ships designed

with a rake of keel the waterline on which this length is measured shall be parallel to the designed waterline.


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Moulded breadth: is the greatest moulded breadth measured inside plating.

Breadth (B) is the greatest moulded breadth of the ship at or below the deepest subdivision load line.

Draught (d) is the vertical distance from the moulded baseline at midlength to the waterline in question.

Depth and the draught both are measured from the top of the keel. The depth is measure from the top of the deck beam. If there is a

camber then allowance is given as 1/3 rd of the camber.

The rest of the meanings are all self-explanatory.


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Definitions

Forward perpendicular

This is represented by a line, which is perpendicular to the intersection of the designed load water-line with the forward side of the

stem.

After perpendicular

A line represents this, which is perpendicular to the intersection of the after edge of the rudderpost with the designed load water line.

This is the case for both single and twin-screw ships. For some ships having no rudderpost, the after perpendicular is taken as the

centre-line of the rudderstock.

Length between perpendiculars

This is the horizontal distance between the forward and after perpendiculars.

Length on the designed load waterline

This is the length, as measured on the water-line of the ship when floating in still water in the loaded, or designed, condition.

Length overall

This is the length measured from the extreme point forward to the extreme point aft.

Base line

This represents the lowest extremity of the moulded surface of the ship. At the point where the moulded base line cuts the midship

section a horizontal line is drawn, and it is this line, which acts as the datum, or base line, for all hydrostatic calculations. This line

may, or may not, be parallel to the load water line depending on the type of ship.


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Moulded depth

This is the vertical distance between the moulded base line and the top of the beams of the uppermost continuous deck measured at the

side amidships.


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Moulded beam

This is the maximum beam, or breadth, of the ship measured inside the inner shell strakes of plating, and usually occurs amidships.

Moulded draught

This is the draught measured to any water-line, either forward or aft, using the moulded base line as a datum.

Extreme beam

This is the maximum breadth including all side plating, permanent fenders etc.

Extreme draught

This is obtained by adding to the draught moulded the distance between the moulded base line and a line touching the lowest point of

the underside of the keel. This line is continued to the FP and AP, where it is used as the datum for the sets of draught marks.



Ship Construction

Ship Stresses

Shear force and bending moments
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When a section such as a beam is carrying a load there is a tendency for some parts to be pushed upwards and for other parts to move

downwards, this tendency is termed Shearing.

The Shear force at a point or station is the vertical force at that point. The shear force at a station may also defined as being the total

load on either the left hand side or the right hand side of the station; load being defined as the difference between the down and the

upward forces, or for a ship the weight would be the downward force and the buoyancy would be the upward thrust or force.

The longitudinal stresses imposed by the weight and buoyancy distribution may give rise to longitudinal shearing stresses. The

maximum shearing stress occurs at the neutral axis and a minimum at the deck and keel. Vertical shearing stresses may also occur.


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Bending Moment

The beam, which we have been considering, would also have a tendency to bend and the bending moment measures this tendency.

Its size depends upon the amount of the load as well as how the load is placed together with the method of support.

Bending moments are calculated in the same way as ordinary moments that is multiplying force by distance, and so they are expressed

in weight length units.

As with the calculation of shear force the bending moment at a station is obtained by considering moments either to the left or to the

right of the station.

Hogging and sagging

Hogging When a beam is loaded or other wise is subjected to external forces such that the beam bends with the ends curving

downwards it is termed as hogging stress.


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For a ship improper loading as well as in a seaway when riding the crest of a wave the unsupported ends of the ship would have a

tendency similar to the beam above.

Sagging In this case the beam is loaded or other wise subjected to external forces making the beam bend in such a way that the ends

curve upwards, this is termed as sagging.

Similar with a ship if improper loaded or when riding the trough of a wave with crests at both ends then the ship is termed to be

sagging.

For Hogging the ship ends to curve downwards would mean that the weight/ load amidships is much less than at the end holds/ tanks.


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For Sagging the ship would have been loaded in such a manner that a greater percentage of the load is around the midship area.

In a seaway the hogging and the sagging stresses are amplified when riding the crests and falling into the troughs. Thus especially for

large ships there are two conditions in the stability software Sea Condition and Harbour condition.

A ship loaded while set in the harbour condition may allow loading with hogging/ sagging stresses reaching a high level, when this

state of loading is transferred to a Sea condition in the software the results would be catastrophic since now the wave motions have

also been incorporated.


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Thus planning a loading should always be in the Sea Condition.


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Discharging in port may be planned in the Harbour Condition.

Hogging and sagging cause compressive and tensile stresses on the ship beam notably on the deck and the keel structure.

Water pressure and Thrust

Pressure is force per unit area and water pressure is dependent on the head of the water column affecting the point of the measurement

of the pressure.


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Let us assume an area of 1sq.m. then this area of water up to a depth of 1 m below the surface would have a volume of 1sq.m. x 1m =

1cbm and the weight of this volume would be 1cbm x density of the water = 1MT (assuming that it is FW) or 1000kgf, therefore the

pressure exerted by this mass would be 1000kgf/sq.m.

Similarly if now the depth of measurement is increased to 3m then the volume of this area subtending up to the 3m mark would be

1sq.m x 3 = 3cbm and the weight of the water would be 3MT or 3000kgf and the pressure exerted would be 3000kgf/sq.m.

If now the liquid had not been FW but any other then the weight would be found by multiplying the volume by the density of the

liquid. And thus the pressure exerted would be found.

If we now increase the area of the square of water plane would it make a difference in the pressure?

Let us consider a area of 2000sq.m then the volume of this water at a depth of 1 m would be 2000cbm and the weight would be

2000MT (consider FW) and the pressure exerted would be 2000,000kgf/ 2000sq.m which would give us again 1000kgf/sqm, thus the

pressure is independent of the area of the water plane.

Thrust however is different, thrust is taken to be the total weight of the liquid over an area. Thus for the previous example the thrust

would be 2000 tonnes.


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Thus the thrust is given by: the area of the water plane x pressure head x density of the liquid.

Thrust always acts at right angles to the immersed surface and for any depth the thrust in any of the directions is the same. Thepressure head which is used in the above calculation of thrust is the depth of the geometrical centre of the area below the surface of the

liquid.

For a ship the thrust on the ship side changes as the depth increases, however the bottom is affected uniformly for a set depth.


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Centre of pressure of an area is the point on the area where the thrust could be considered to act. It is taken that the centre of pressure

is at 2/3rds the depth below the surface for ordinary vertical bulkheads and at half the depth in the case of collision bulkheads.

Racking stress and its causes

In a seaway as a ship rolls from one side to the other the different areas of the ship have motion which are dependent on the nature of

the subject area. The accelerations are thus not similar due to the various masses of the different sections (although joined together).

These accelerations on the ships structure are liable to cause distortion in the transverse section. The greatest effect is under light ship

conditions.

Local Stresses

Panting

This is a stress, which occurs at the ends of a vessel due to variations in water pressure on the shell plating as the vessel pitches in a

seaway. The effect is accentuated at the bow when making headway.


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Pounding:

Heavy pitching assisted by heaving as the whole vessel is lifted in a seaway and again as the vessel slams down on the water is known

as pounding or slamming. This may subject the forepart to severe blows from the sea. The greatest effect is experienced in the light

ship condition.


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Stresses caused by localized loading

Localized heavy loads may give rise to localized distortion of the transverse section.

Such local loads may be the machinery (Main engine) in the engine room or the loading of concentrated ore in the holds.


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Shearing force Curve

The following example shown is for an old tanker in the ballast condition.

The compartments loaded are the Fpk tank, WB tanks 2P and 2S, WB tank 3C and other miscellaneous tanks in the after section of the

tanker.

The SF is calculated as per the manual with the multipliers having been set by the shipyard and approved by the classification society.

If we are to assume that the ship is a beam then the loads are at the fore end midship region and the after section which has the

accommodation as well as the ER.


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The SF curve is reproduced and the maximum occur at frames 54 and between 68 to 72, this corresponds to the area on the ship mid

4C and between 2C (aft to mid region). Note that the signs have changed between the frames 54 and 68 with a point between frames

59 to 63 (3C mid to aft) registering 0 value.


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Bending Moment Curve

The following example shown is for a old tanker in the ballast condition.

The compartments loaded are the Fpk tank, WB tanks 2P and 2S, WB tank 3C and other miscellaneous tanks in the after section of the

tanker.

The BM is calculated as per the manual with the multipliers having been set by the shipyard and approved by the classification

society.

If we are to assume that the ship is a beam then the loads are at the fore end midship region and the after section which has the

accommodation as well as the ER.


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The BM curve is reproduced and the maximum occur at frames 59 and 76, this corresponds to the area on the ship 4C forward

bulkhead and 2C forward bulkhead. Note that the signs have changed twice.


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Ship ConstructionHull Structure

Structural components on ships plans and drawings: frames, floors, transverse frames, deck beams, knees, brackets, shell plating,

decks, tank top, stringers, bulkheads and stiffeners, pillars, hatch girders and beams, coamings, bulwarks


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Bow and stern framing, cant beams, breasthooks


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Description of standard steel sections: flat plate, offset bulb plate, equal angle, unequal angle, channel, and tee


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Longitudinal, transverse and combined systems of framing on transverse sections of the ships

Longitudinal framing Open floors

Longitudinal framing Plate floors


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Transverse framing Open floors

Transverse framing Plate floors


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Duct keel


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Stress concentration in the deck round hatch openings

Holes cut in the deck plating by way of hatchways, masts and others create areas of high local stress due to lack of continuity created

by the opening.

Compensation for loss of strength at hatch openings

Compensation around some of these openings may be overcome by increasing the sizes of the material used, buy a careful disposition

of the material and by paying careful attention to the structural design.

Compensating for the stress concentration around hatch corners by rounding off the square hatch corner ends


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The corners radiused to reduce the stress concentration


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A hatch corner in plan view, showing the structural arrangements

A transverse section through a hatch coaming, showing the arrangement of coamings and deep webs


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Deck-freeing arrangements - scuppers, freeing ports, and open rails


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Connection of superstructures to the hull at the ships side

A plane bulkhead, showing connections to deck, sides and double bottom and the arrangement of stiffeners


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A corrugated bulkhead


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Transverse bulkheads have vertical corrugations and fore and aft bulkheads have horizontal ones

The basic idea of a bulkhead in addition to the water tight integrity is to add to the girder strength of the ship beam.

Thus for a transverse bulkhead, which extends from the port to the starboard side or vice versa, the framing is done in a vertical

manner so that the compressive and the tensile stress may be reduced for the beam.


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Similarly for a longitudinal bulkhead which runs parallel to the shipside the framing is done vertically, again so that the additional

strength would enhance the stress compensating effect of the ship beam.


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Construction of the corrugated bulkhead

A fitted corrugated bulkhead


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Purpose of bilge keels and their attachment to the ships side

Bilge keels are fitted at the turn of the bilge to resist rolling. They also improve the steering qualities of the ship though very

slightly.

The ends are to be gradually tapered and should not end on an un-stiffened panel.


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Stress relieving while fitting the bilge keel

Hold drainage systems

The hold drainage system of older cargo vessels had limber board covered upper side of the tank side bracket areas. The drainage

conduit was these areas and the pipelines were connected to the after ends, which passed through the lightening holes in the DBs.


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The limber boards were removable for cleaning as they were frequently damaged (edges) leaving gaps through which cargo residue

would accumulate.

Modern ships do not have the side bilges and have only a strum box at the after end of the holds and these are connected in the similar

way to pipelines, which run through the DBs.


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Ship ConstructionRudder and Propellers


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The shape of a rudder plays an important part in its efficiency. The area of the rudder is approximately 2% of the product of the length

of the ship and the designed draught.

Since the vertical dimensions of the rudder are somewhat restricted due to the area constraint as mentioned above, the fore and aft

dimensions are increased.


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Again due to this increased dimensions the torque necessary to turn this rudder is overcome by fitting balanced or semi balanced

rudders. Such a rudder has about 1/3rd of the rudder area forward of the turning axis.

An ideal rudder is one where the centre of pressure and the turning axis coincide for all angles of the helm.

An unbalanced rudder consists of a number of pintles and gudgeons, the top pintle being the locking pintle which prevents any vertical

movement in the rudder and the pintle And gudgeon taking the weight of the rudder.


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Principle of screw propulsion

Some people still occasionally refer to the propeller as the airscrew, a very accurate and descriptive term that reflects the basic

design and function of the propeller.

Leonardo da Vinci had proposed the concept of a helical screw to power a machine vertically into the air.

The propeller uses that principle to provide propulsion through the air, much like a threaded screw advances through a solid medium,

with some notable exceptions, primarily related to the loss of forward movement because the medium is not solid.

Nonetheless, the propeller is similar to a screw in some common features. First, the pitch of a propeller is the theoretical distance the

propeller would move forward in one revolution (similar to a screw) and conceptually is the same as the pitch of a screw, namely the

distance between threads if the propeller were a continuous helix.

The second feature that relates to its screw design is that the angle of the blade changes along the radius, so that close to the hub, the

angle is very steep and at the tip of the blade it is much more shallow.

From a practical standpoint, this means that unless the pitch for a given propeller is known, it requires a trigonometric calculation to

determine the pitch empirically.

Thirdly, just as screws come in left hand and right hand threads, propellers have the same designation. When facing the water/ air

flow if the top of the propeller moves to the right, it is designated Right Hand and if to the left it is Left Hand. (As viewed from

the front a right hand propeller turns counterclockwise and a left hand propeller turns clockwise.) Propellers will frequently be

stamped as RH orLH.


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Propeller and some definitions


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Boss or Hub

The central portion of a screw propeller to which the blades are attached and through which the driving shaft is fitted.


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Rake

The point displacement, from the propeller plane to the generator line in the direction of the shaft axis. Aft displacement is considered

positive rake (see Figure 2). The rake at the blade tip or the rake angle are generally used as measures of the rake. The strength criteria

of some classification societies use other definitions for rake.


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Skew

The displacement of any blade section along the pitch helix measured from the generator line to the reference point of the section (see

Figure 2). Positive skew- back is opposite to the direction of ahead motion of the blade section. The skew definition pertains to

midchord skew, unless specified otherwise.

Back (of blade)

The side of a propeller blade which faces generally in the direction of ahead motion. This side of the blade is also known as the

suction side of the blade because the average pressure there is lower than the pressure on the face of the blade during normal ahead

operation.

Tip

The maximum reach of the blade from the center of the propeller hub. It separates the leading edge from the trailing edge.

Radius

Radius of any point on a propeller.

Pitch

The pitch of a propeller is the theoretical distance the propeller would move forward in one revolution (similar to a screw) and

conceptually is the same as the pitch of a screw, namely the distance between threads if the propeller were a screw. For this reason,

propellers will frequently be stamped with a designation such as D 2550/P2610. This means that the diameter (in this case length of

propeller or thickness of a screw) is 2.550 meters, and the pitch is 2.610 meters, so that in a mathematical sense, one revolution of this

propeller would move it forward a distance of 2.610 meters.


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Comparing fixed-pitch with controllable-pitch propellers

Advantages of a controllable pitch propeller

Allow greater manoeuvrability

Allow engines to operate at optimum revs

Removes need for reversing engines

Reduced size of Air Start Compressors and receivers

Improves propulsion efficiency at lower loads

Disadvantages

Greater initial cost

Increased complexity and maintenance requirements

Increase stern tube loading due to increase weight of assembly, the stern tube bearing diameter is larger to accept the larger diameter

shaft required to allow room for Oil Tube

Lower propulsive efficiency at maximum continuous rating

Prop shaft must be removed outboard requiring rudder to be removed for all prop maintenance.

Increased risk of pollution due to leak seals


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Sketches the arrangement of an oil-lubricated sterntube and tailshaft

Stern tubes are fitted to provide a bearing for the tail end shaft and to enable a watertight gland to be fitted at an accessible position.

The tube is usually constructed of cast steel with a flange at its forward end and a thread at the after end. It is inserted from forward

and this end is bolted over packing to the after peak bulkhead. A large nut is placed over the thread at the after end, tightened and

secured to the propeller post.

In an oil lubricated stern tube the bearings are made of white metal. A gland is fitted to each end of the stern tube and since the after

end gland will not be accessible during sea service it is made self adjusting. The flange shown is attached to the propeller so that it

rotates with the shaft and oil tightness is obtained by a rotating gland.


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States how the propeller is attached to the tailshaft

The after end of the tail end shaft is tapered to receive the propeller boss and a key is provided to transfer the torque from the shaft to

the propeller. A nut fitted with a locking plate secures the propeller in position and as an additional safeguard it is fitted with a left

hand thread in association with a right hand ed propeller or vice versa.

To remove the propeller and the tail end shaft the propeller should be slung on special eyes provide on the shell for this purpose the

rope guards removed and the propeller nut slackened.

The propeller is then started from the shaft by driving steel wedges between the boss and the propeller post. When it is free the nut is

removed.

Cross-section of a shaft tunnel


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Ship ConstructionFittings

Mechanical Hatch covers

The figures shown below illustrate the various parts of a mechanical hatch cover. These hatch covers may be made up of several

individual pontoons (so named because prior to the MacGregor type of rolling hatch covers the pontoons had to be individually lifted

and battened down).


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The pontoons (individual parts of the hatch covers) are connected to one another and can easily and quickly be rolled into or out of

position leaving clear hatchways and decks. The normal practice for the lengthwise opening of hatches but sideways opening

hatchways are found on large bulk carriers and OBOs.

The smaller versions are mainly operated either manually (using wire and winch) or electrically. The larger ones are nearly all operated

hydraulically.


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The wheels on the side on which the pontoons rollere are eccentric in their construction thus when in the battened (lowered) position

the clearance between the wheel and the trackway is minimum and the pontoon sits on the trackway, the rubber gaskets being

compressed by the compression bar.

The cross wedges are used to ensure the pontoon rubber gaskets compress against the compression bars of the forward pontoons.


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The side cleats ensure that the pontoons stay compressed to the trackway compression bar and the ship motion is effectively

compensated or removed.


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These hatch cover systems consist of various parts:

The pontoons, eccentric wheels, trackway wheels, cross wedges, and the side cleats.

Battening down a hatch is to be done after reading the operations manual.

A hatch cover should not be battened with cargo on top.


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The Channels are to be swept prior battening so that the packing do not rest on dirt.

The drain channel on the front of the hatch pontoons are to be cleaned prior closing the hatch.

Once the wheels are turned the next item to be engaged are the cross wedges and the side cleats are to be fitted last.


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Prior proceeding to sea (long voyage) the hatch cover sealing should be tested with chalk marks made on all the compression bars on

the hatch coaming as well as on the pontoons. The hatch is to be battened and then opened to see if all the rubber gaskets have got

chalk mark on them or not if not hen rectification to be done.


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Oil tight hatchcover

These hatch covers are small in size and may have butterfly nut locking arrangement. The sealing is done by Hi-nitrile rubber which is

not affected by oil.

Manhole covers do not vary much in design, their shape however are sometimes different for different places.

When fitted outside a tank they may be either circular or elliptical. But when fitted inside they are almost always elliptical to facilitate

their removal.

Usual size openings vary between 450mm to about 600mm.


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Roller, Multi-angle, Pedestal and Panama fairleads

A roller is to be found on the forward and after stations area generally at the leads to the mooring ropes as well as on top of old

man pedestals.

These facilitate the hauling of ropes since they reduce the friction when the rope is hauled through a panama fairlead which has no

rollers.


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A panama fairlead is o named since they were mostly used in the Panama Canal. The ship is hauled by small locomotives and the

wires are sent out through these leads they are of adequate strength to prevent the metal being cut open by the wires.

A multi angle fairlead again is a fairlead used due necessity when in the great Lakes. The ship moves through numerous locks as the

ship is made to climb a great height the Welland Canal system itself uses about 13 lock gates to cross the Niagara falls. The


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movement of the ship being fast and the difference in height being enormous the ship steadies itself with 2 wires forward and 2 wires

aft, when in the locks. These wires are passed through the multi angle fairleads to reduce the enormous friction generated.


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Mooring bitts are prefabricated and then are welded onto the deck. The size of the bitts are dependent on their use. Thus a small set

may be fitted next to an occasional winch while the larger ones are fitted at the mooring stations.

The bitts are hollow and as such require care to ensure that the sides do not corroded and holed.


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Securing anchors and making spurling pipes watertight in preparation for a sea passage

Once the anchor has been washed the anchor is hove right up into the hawse pipe, the bow stopper is lowered and the locking pin

inserted.

The winch is reversed a little to make the chain sit properly into the slot of the bow stopper and then the brake is tightened and the

windlass gear removed.


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The anchor chain at the deck level (hawse pipe) is lashed with extra lashings as provided by the shipyard, if none are present or if

expecting heavy weather, then extra wire rope lashings are taken, The wire rope to be used should be tested one, if an old (good

condition) life boat falls are available then this makes a very good extra lashing wire. This wire is flexible and can be used by hand. A

number of turns (figure of eight) are taken around two sets of bitts. The free ends being fastened by bull dog clips at least two fixed in

opposite directions.

Generally the shipyard would have provide lashing point as well as short length of wire attached to a bottle screw. These should be

well oiled and are the most efficient for lashing the anchor. The wire should be tight.

Once the anchor is lashed the hawse pipe covers are not placed but stowed under deck or in their stowage positions.

The spurling pipe area is chipped to remove any residual remains of earlier cement.

The metal spurling pipe covers are placed around the chain and over the spurling pile. The clips provided at the edges of the coversshould be hooked to the lips of the spurling pipe.

A new canvas cover is then placed over the metal covers just fitted and is tied around the lips of the spurling pipe as well as the chain.

No empty spaces should be found.

Cement mixture is prepared and the entire cover is covered with this mixture.

Cable stopper

A chain stopper as shown below may be of various designs, but all serve the same purpose to hold the cable.

The cable is passed through the stopper with the holding bar lifted up by the counterweight on top. There is a pin to hold the bar in

this position.

Once the decision has been taken to hold the cable, the safety locking pin is removed and the bar is eased down on top of the cable.

Note that the default position of the holding bar is to arrest the cable, only a effort is required to keep it up.

O h b i l d h bl h bl h b dj d li l h h fl f h bl f ll i h


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Once the bar is placed over the cable the cable may have to be adjusted a little to ensure that the flat part of the cable falls in the

holding area and not the vertical section, the safety locking pin is now introduced to prevent the bar from jumping u[ in case the cable

slip from the brake.

Once the lacking pin is in position the brake can be released and the stopper would do the work of holding the cable.


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Masts and Sampson posts


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Bilge and ballast piping system of a cargo ship

The following shows a bilge and ballast line diagram of a general cargo ship.

The bilges are all fitted with non return valves so that not water may be inadvertently be pumped into the holds.

The bilges are serviced by a bilge pump which incorporates a strainer and this should be checked before starting the pump.


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The strum box fitted in the holds is to be kept clean and the perforations are to be checked that they are not closed due to muck and


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The strum box fitted in the holds is to be kept clean and the perforations are to be checked that they are not closed due to muck and

rust.

Same with the mud boxes in the ER fitted into the system.

Arrangement of a fire main

Capacity of fire pumps

The capacity of the fire pumps is stated in SOLAS but need not exceed 25m 3 per hour

Arrangements of fire pumps and of fire mains


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Arrangements of fire pumps and of fire mains

Ships shall be provided with independently driven fire pumps as follows:

Passenger ships of 4,000 tons gross tonnage and upwards at least three

Passenger ships of less than 4,000 gross tonnage and cargo ships of 1,000 tons gross tonnage and upwards at least two

Cargo ships of less than 1,000 tons gross tonnage to the satisfaction of the Administration

Sanitary, ballast, bilge or general service pumps may be accepted as fire pumps, provided that they are not normally used for pumping

oil and that if they are subject to occasional duty for the transfer or pumping of oil fuel, suitable change-over arrangements are fitted.

The arrangement of sea connections, fire pumps and their sources of power shall be such as to ensure that:

In passenger ships of 1,000 gross tonnage and upwards, in the event of a fire in any one compartment all the fire pumps will not be put

out of action.

In cargo ships of 2,000 gross tonnage and upwards, if a fire in any one compartment could put all the pumps out of action there shall

be an alternative means consisting of a fixed independently driven emergency pump which shall be capable of supplying two jets of

water to the satisfaction of the Administration. The pump and its location shall comply with the following requirements:

The capacity of the pump shall not be less than 40% of the total capacity of the fire pumps required by this regulation and in any case

not less than 25 m3/h.

Number and position of hydrants

The number and position of hydrants shall be such that at least two jets of water not emanating from the same hydrant, one of which

shall be from a single length of hose, may reach any part of the ship normally accessible to the passengers or crew while the ship is

being navigated and any part of any cargo space when empty, any ro-ro cargo space or any special category space in which latter case

the two jets shall reach any part of such space each from a single length of hose Furthermore such hydrants shall be positioned near


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the two jets shall reach any part of such space, each from a single length of hose. Furthermore, such hydrants shall be positioned near

the accesses to the protected spaces.

Pipes and hydrants

Mainly galvanised steel pipes are used and during repairs no doublers or such part renewals are allowed change is flange to flangerenewal.

The arrangement of pipes and hydrants are to be such as to avoid the possibility of freezing.

On cargo ships where deck cargo may be carried, the positions of the hydrants are to be such that they are always readily accessible

and the pipes are to be arranged, as far as practicable, to avoid risk of damage by such cargo.

A valve is to be fitted at each fire hydrant so that any fire-hose may be removed while the fire pump is at work.


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The above figure shows a typical fire mains line. Note that the emergency fire pump is located away from the machinery space as perrules.

Isolation valves are provided so that any system being damaged the other system may be used for example the port system and the

starboard system.

In the machinery space a separate pump (Fire and GS pump) is also coupled, this is generally used when washing decks, and as an


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In the machinery space a separate pump (Fire and GS pump) is also coupled, this is generally used when washing decks, and as an

emergency measure while the fire pump is being overhauled.

Sounding pipes

Sounding pipes covers come with varied designs. That shown below is a sunken cap type generally the cap is made of brass. Thejustification being that of the two thread and cap assembly the thread of the brass is to wear out first and that of the deck pad. The

renewal of the brass cap being inexpensive and convenient rather than the deck pad which entails hot work.

The metal cap (not sunken) type of covers have a chain attached to them to prevent their being washed overboard.


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Air pipes to ballast tanks or fuel oil tanks


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Air pipes to ballast tanks or fuel oil tanks

The above figure shows a design of air pipe cover.

In normal condition the ball remains at the bottom of the air pipe head and the tank breathes in and out through the vent.

However in the event that the air pipe is submerged then the ball floats up and closes the opening at the top thus preventing any water


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p p g p p g p p g y

from entering the tank.

Sea spray and rain is prevented from entering the tank by the design of the head. It is totally enclosed and a rectangular plate, which

leaves a small gap between the mesh and itself, allowing the breathing of the tank.

Fittings and lashings for the carriage of containers on deck


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Fittings and lashings for the carriage of containers on deck

In the figure above the containers on deck are loaded on top of shoes which are welded on top of the deck as well on top of the hatch


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covers.

Twistlocks are fitted on the shoes and the containers placed on the twistlocks. Hinged eyes are welded on deck to secure the container

rod lashings.


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Nautical Term en Logy

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