Oil Tanker Construction Rules

7/27/2019 Oil Tanker Construction Rules

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Oil Tanker Construction


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Construction Rules

These requirements apply to tankers for the carriage of

flammable, toxic, corrosive or otherwise hazardous liquids.

International and national regulations remain unaffected.

For the purposes of these Rules, tankers are:

a. Ships for the carriage of liquids in tanks which form part ofthe hull, and

b. Ships with fixed tanks independent of the hull and used for

the carriage of liquids.


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Construction Rules

SOLAS I Reg 2 defines a tanker as a cargo ship constructed

or adapted for the carriage in bulk of liquid cargoes of an

inflammable nature.

Requirements for tankers in this chapter shall apply to

tankers carrying crude oil or petroleum products having a

flashpoint not exceeding 60C (closed cup test), as determined

by an approved flashpoint apparatus, and a Reid vapour

pressure which is below the atmospheric pressure or other

liquid products having a similar fire hazard.


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Construction Rules

IMO Oil Tanker Category:

Category

1 : Commonly known as pre MARPOL oil tankers of

size 20,000 dwt and above to carry Crude oil, Fuel Oil, Lubricating

Oil or Heavy Diesel Oil as cargo and of 30,000 and above carrying

other oils, which do not comply with requirements for protectively

located segregated ballast tanks.

Category2 : Commonly known as MARPOL oil tankers of size

20,000 dwt and above to carry Crude oil, Fuel Oil, Lubricating Oil

or Heavy Diesel Oil as cargo and of 30,000 and above carrying

other oils, which do comply with requirements for protectivelylocated segregated ballast tanks.

Category3 :Oil tankers of 5000dwt and above but less than dwt

specified for Categories 1 and 2.


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Pre-MARPOL Oil Tanker
http://en.wikipedia.org/wiki/File:Pre-MARPOL_tanker.svg


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MARPOL Oil Tanker
http://en.wikipedia.org/wiki/File:MARPOL_tanker.svg


7/84Double Hull Oil Tanker
http://en.wikipedia.org/wiki/File:Double_Hull_Tanker.svg


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Construction Rules

Irrespective of the size of the tankers, the main criteria

adopted during design and construction are with regard to:

1. Prevention of Hazards from the cargo and cargo vapour.

2. Prevention of Pollution hazard.

3. Prevention of fire hazard. Each of the above objectives are achieved only when a

tanker is constructed as well as operated in accordance with

well established rules and regulations.

Most of the rules regarding design and construction are asper SOLAS and MARPOL regulations and also

classification societies have their rules which normally are in

line with the IMO rules.


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Construction Rules

The safe operations of tankers are achieved by following the

safe operating procedures geven in publications likeInternational Safety Guide for Oil Tankers and

Terminals(ISGOTT) and International Safety Guide for Inland

Navigation Tank barges and Terminals(ISINTT) published by

various organisations like Oil Companies International MarineForum(OCIMF), Central Commission for the Navigation of

Rhine(CCNR), International Chamber of Shipping(ICS) and

International Association of Ports and Harbours(IAPH).

Also in the Safety Management System Manual required by

the ISM code the safe operating procedures are to be given for

various operations onboard the ships.


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Construction Rules

Dating back to the Congress of Vienna (1815), the Central

Commission for Navigation on the Rhine is the oldest internationalorganisation in modern history and was established with an objectiveof controlling the river transport through Rhine.

The Oil Companies International Marine Forum (OCIMF) is a

voluntary association of oil companies established in1970 with aninterest in the shipment and terminalling of crude oil, oil products,petrochemicals and gas with an objective of achieving safe andenvironmentally responsible operation of oil tankers, terminals andoffshore support vessels, promoting continuous improvement in

standards of design and operation.

International Chamber of shipping is the principal international tradeassociation for the international shipping industry, representing allsectors and trades of shipping and was established in 1921.


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Construction Rules

International Association of Ports and Harbours(IAPH) was formed in

1955 and head quarters is in Tokyo with an objective to Promote theinterest of ports worldwide through strong member relationships,

collaboration and information-sharing that help resolve common

issues, advance sustainable practices and continually improve how

ports serve the maritime industries.

IACS was founded on September 11, 1968, in Hamburg, Germany

they are the technical body formulating precise rules for the

construction of ships in line with IMO regulations.

Although IACS is a non-governmental organization, it also plays a

role within the International Maritime Organization (IMO), for which

IACS provides technical support and guidance and develops unified

interpretations of the international statutory regulations developed by

the member states of the IMO.


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Construction Rules

Once adopted, these interpretations are applied by each IACS

member society, when certifying compliance with the statutoryregulations on behalf of authorizing flag States.

IACS has consultative status with the IMO, and remains the only

non-governmental organization with observer status which also

develops and applies technical rules that are reflective of the aims

embodied within IMO conventions.


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Construction Rules-Hull Design


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4. On crude oil tankers>20000dwt and product carriers

>30000dwt, the aggregate capacity of all ballast shall not beless than the SBT capacity required under regulation 13 to

meet the IMO draft and trim requirements.

5. Suction wells of cargo tanks may protrude into the DB tank

below provided that the well is made as small as possible

and the height of the suction well from the bottom is not less

than 0.5h from the bottom shell plating.

6. Ballast, Vent pipes and Sounding pipes shall not pass

through cargo tanks and vice versa; except for short lengths

of pipes which has to be of complete welded construction or

equivalent.


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Oil shall not be carried in spaces forward of the collision

bulk head or similar bulk head in the location.

The double bottom tank may be dispensed with if the weight

of the cargo plus the vapor pressure is less than the outside

water pressure, so that in the event of a hull failure the out

side water pressure will prevent the out flow of oil, like in

mid deck design.

Here the depth of cargo tank is calculated as follows:

1.1x Depth of Cargo x Cargo density x g + 100p < minimumdraft x Density of sea water x g.

Where:

g = Acceleration due to gravity, p = maximum set pressure

of P/V valve.


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In the mid deck design construction the height of middle

deck shall be located at least B/6 or 6m which is less fromthe bottom, but not more than 0.6D, where D is the

moulded depth amidships.

The wing tank partition shall extend up to the bottom shell.

Oil tankers < 5000dwt shall be fitted with double bottom

tanks of height = B/15 subject to a minimum of 0.76m.

In the turn of the bilge area, the tank top shall extend parallel

to the line of mid-ship flat bottom to meet the ship side. Cargo tanks on these ships must not have a capacity of more

than 700m3 or else wing tanks will have to be provided

having a width of;

w = 0.4 + 2.4 DW/20000m but not less than 0.76m.


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Stability of Double Hull Design

In smaller double hull tankers the two longitudinal divisions

are omitted from a single centre tank and hence the freesurface effect is increased.

Due to the second outer hull the centre of gravity of the

cargo is raised causing a reduction in GM.

Oil carriers of 5 000 tonnes deadweight and above and delivered

after 1st February 2002 shall comply with the intact stability

criteria as specified in MARPOL Annex I, Reg. 27.

For ships loading and or offloading in port only, the GM

corrected for free surfaces measured at 0 heel shall be not less

than 0.15 m.

In practice the resulting GM in modern smaller size (Panamax)

double tankers are very near to the above value.


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Stability of Double Hull Design

The greatest problem occurs towards completion of loading

or initial stages of discharging when the tanks are almost fulland the ballast is almost empty with both ballast and cargo

providing free surface effect and raising KG.

At these stages the concerned officers should take extreme

care not to reach the angle of loll, especially when multiple

tanks are loaded or discharged.


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Mid Deck Design


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Other than the above designs may also be accepted by IMO

provided that they offer equal amount of protection incase ofa damage to the hull.

One such revolutionary design was the Coulombi eggdesign created by the Swedish naval engineer Anders

Bjokman. It constituted a feasible and efficient alternative to the double

hull, and in fact, won the approval of the IMO in September1997, under MARPOL annexe 1-13 F.

However, the US government (U.S.G.C.) Maintained thesupremacy of the double hull, pursuant to the OPA, and sothe Coulumbi egg was reduced to the status of merely aninteresting research project.


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ons ruc on u es ou e u


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ons ruc on u es- ou e uDesign

Sandwich Design: This is the most popular design in which

the webs and stiffeners are located in the double hull spaces.


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Construction Rules-Double Hull Design

Minimum Double Bottom/Maximum Double Side: This

design has a 2m deep DB and 5m wide DS with an innerbottom longitudinal fitted in the cargo tanks.

70% of the ballast is carried in the side tanks, and hence rest

of the ballast may be taken in DB tanks at open sea, prevents

sediment accumulation in DB tanks.

Other Designs: Depending on the Double hull width and

Double Bottom height, the double hull tanker constructions

may be termed as 1/3rd-2/3rd design, Minimum 2m DH

design etc.

Unidirectionally Stiffened Double Bottom: In this design

one longitudinal girder and two longitudinal stiffeners are

provided instead of inner and outer longitudinals.


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Construction Rules-Double Hull Design

When the double bottom height is 2m with 0.6m deep

longitudinals, we have the unidirectional stiffened doublebottom with no transverse webs inside double bottom.

This construction is simple and double bottom spaces can be

easily ventilated and washed.


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Disadvantages of Double Hull Design

The transition from single to double hulled vessels has been

driven by the imperatives of safety and environmentalprotection.

The paradox is that the resulting ships are more complex thanbefore, with a substantial increase in the number of fatigue

and corrosion prone details, where risk of initiating structuralfailure can occur.

As well as the basic requirement for tankers to have doublehulls, there are now additional regulatory measures stipulatingincreased survey and maintenance (including access forinspection) on tankers.

It has been argued that similar standards of inspection andmaintenance of single hulled ships would have resulted in asimilar improvement to safety, but at a lower cost.


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In one of the study of comparison of single and double hull

tankers, the following were clearly observed viz:

1. Oil outflow and considerations of hydrostatic balance

following collisions and grounding.

2. The difficulties of salvaging a double hulled vessel due to

flooding and lost buoyancy following a grounding incident.

3. The intact and damaged stability of double hulled tankers

was also questioned, due to concerns over the raised centre

of gravity associated with double bottom tanks and thegreater free surfaces of wide tanks.


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Double hulled tankers have a high level of structural

complexity, the number of structural intersections is almosttwice that of an equivalent size single hull ship.

Leakages of cargo into the ballast spaces from cracks in the

inner hull structure were seen as a major risk.

Fatigue and corrosion were highlighted as potential causes of

such failures.

In the following figure the common areas of stress

concentration and fatigue failure are shown. These include connections of inner hull plating at the upper

and lower intersections of the sloping hopper, connections at

the toes of brackets and stringers and the intersections of

secondary longitudinal stiffeners with transverse members.


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Depending on their location, geometric configuration and

construction, a combination of service loads, residual stressesand corrosion can result in coating breakdown and fatiguecracks.

This can lead to ongoing propagation and eventual structural

failure. Use of higher tensile steel has also contributed to fatigue

failures.

Undetected corrosion has been a major cause of some of the

most noteworthy marine disasters. A paper produced by OCIMF highlights the difficulties of

coating, inspecting and maintaining the ballast spaces, with acomplex arrangement of internal stiffeners, brackets andassociated structural details.


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It is clear that control of corrosion plays a major part in the

safe operation and maintenance of a double hulled tanker.

Conventional steel designs, with their inherent complexity are

costly to protect and maintain.

This is due to the large surface areas, difficulty of access and

large numbers of points for potential initiation of coating

breakdown.

Todays double hulled tankers are not known to be suffering

from structural failures. However, the effort required to design and construct

intersections with good service performance adds considerably

to the production cost and the problems have not been

completely eliminated.


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Cargo equipments

Location of Cargo Pumps: Cargo pumps are to be

located on deck, in the cargo tanks or in special pumprooms separated from other ship's spaces by gastight

decks and bulkheads.

Pump rooms shall be accessible only from the cargo areaand shall not be connected to engine rooms or spaces

which contain sources of ignition.

Penetrations of pump room bulkheads by shafts are to be

fitted with gastight seals. Provision shall be made for lubricating the seals from

outside the pump room.


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Overheating of the seals and the generation of sparks are

to be avoided by appropriate design and the choice of

suitable materials.

Where steel bellows are used in gastight bulkhead

penetrations, they are to be subjected to a pressure test at 5

bar prior to fitting.


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Cargo equipments

Suitable arrangements are to be provided for cargo pumps to

prevent damage due to over pressure. It shall be possible to control the capacity of the cargo pumps both

from the pump room and from a suitable location outside this room.

Means are to be provided for stopping cargo pumps from a position

above the tank deck. At all pump operating positions and cargo handling positions on

deck, pressure gauges for monitoring pump pressures are to be

fitted.

The maximum permissible working pressure is to be indicated by ared mark on the scale.

The drain pipes of steam-driven pumps and steam lines shall

terminate at a sufficient height above the bilge bottom to prevent

the ingress of cargo residues.


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Cargo equipments

Drive motors are to be installed outside the cargo area.

Exceptions are steam-driven machines where the steamtemperature does not exceed 220 C.

Hydraulic cargo pump driving machinery (e.g. for submerged

pumps) may be installed inside the cargo area.

Cargo line systems shall be permanently installed and

completely separated from other piping systems.

In general they may not extend beyond the cargo area.

Cargo lines are to be so installed that any remaining cargo canbe drained into the cargo tanks.

Filling pipes for cargo tanks are to extend down to the bottom

of the tank.


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Cargo equipments

Expansion bends, expansion bellows and other approved

expansion joints are to be fitted as necessary.

Sea water inlets shall be separated from cargo lines e.g. by

two stop valves, one of which is to be locked in the closed

position.

Sea water in- and outlets (sea chests) for ballast and cargo

systems are to be arranged separately.

Welding is the preferred method of connecting cargo lines.

Cargo oil pipes shall not pass through ballast tanks. Hose connections are to be made of cast steel or other ductile

materials and are to be fitted with shut-off valves and blind

flanges.


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Cargo equipments

Extension rods for stop valves inside cargo tanks are to be fitted

with gastight deck penetrations and open/closed indicators. All other stop valves are to be so designed as to indicate whether

they are open or closed.

Emergency operating mechanisms are to be provided for stop

valves in cargo tanks which are actuated hydraulically orpneumatically.

Hand-operated pumps which are connected to the hydraulic system

in such a way that they can be isolated may be regarded as

emergency operating mechanisms. An emergency operating mechanism controlled from the deck can

be dispensed with provided that the cargo tank can be emptied by

another line or the shutoff valve is located in the adjacent tank.


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Cargo equipments

At the positions for monitoring the cargo loading and discharging

operations, the cargo lines are to be fitted with pressure gauges witha red mark denoting the maximum permissible working pressure.

Provision shall be made for the safe draining, gas-freeing and

cleaning of the cargo line system.

Steam lines to the individual heating coils of the cargo tanks are tobe fitted with screw-down non-return valves.

Means of testing the condensate for ingress of oil are to be fitted

before the stop valves in the heating coil outlets.

The condensate from the heating system is to be returned to thefeed water system via observation tanks.

Condensate observation tanks are to be arranged and equipped such

that cargo residues in the condensate will not constitute a hazard in

engine room or other gas safe spaces.


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Cargo equipments

Vent pipes shall be fitted with flame arresters and shall be led

to the open deck in a safe position.

Steam lines for steaming out cargo tanks and cargo lines are to

be fitted with screw-down non-return valves.

f


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Bilge pumping of cargo pump rooms and

cofferdams in the cargo area

Bilge pumping equipment is to be located in the cargo area toserve the cargo pump rooms and cofferdams.

A cargo pump may also be used as a bilge pump.

On oil tankers used exclusively for the carriage of flammable

liquids with flash points above 60 C, cargo pump rooms andcofferdams may be connected to the engine room bilge

system.

Where a cargo pump is used as bilge pump, measures are to be

taken, e.g. by fitting screw-down non-return valves, to ensure

that cargo cannot enter the bilge system.

Where the bilge line can be pressurised from the cargo system,

an additional non-return valve is to be fitted.

Bil i f d


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Bilge pumping of cargo pump rooms and

cofferdams in the cargo area

Means shall be provided for pumping the bilges when specialcircumstances render the pump room inaccessible.

The equipment necessary for this is to be capable of being

operated from outside the pump room or from the pump room

casing above the tank deck (freeboard deck).


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Ballast systems in the cargo area

Means for ballasting segregated ballast tanks adjacent to cargotanks shall be located in the cargo area and are to be

independent of piping systems forward and aft of the

cofferdams.

On oil tankers an emergency discharge connection through aspool piece to cargo pumps may be provided.

A non-return device in the ballast system shall be provided to

prevent the backflow of cargo into ballast tanks.

The spool piece together with a warning notice shall be

mounted in a conspicuous location in pump room.

Ballast water pipes, sounding and air pipes shall not pass

through cargo oil tanks.


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Ballast systems in the cargo area


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Ventilation and gas-freeing

Ventilation of cargo and ballast pump rooms in the cargoarea:

Pump rooms are to be ventilated by mechanically driven fansof the extraction type.

Fresh air is to be induced into the pump room from above.

These ventilation systems shall not be connected to those ofother spaces.

The exhaust duct is to be so installed that its suction opening

is close to the bottom of the pump room. An emergency suction opening is to be located about 2 m

above the pump room floor.

This opening is to be fitted with a means of closing which canalso be operated from the main deck.


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Gas-freeing of cargo tanks, double hull spaces, ballasttanks, pipe tunnels and cofferdams:

Provision shall be made for the gas-freeing of cargo tanks,

double hull spaces, ballast tanks, pipe tunnels and cofferdams.

Where fans are permanently fitted for gas-freeing of tankshaving connections to cargo oil lines, measures are to be

taken, e.g. by removing spool pieces of the ventilation ducting

or by using blank flanges, to ensure that neither cargo nor

vapours can penetrate into the fans when not in use.

The inlet openings in cargo tanks used for gas-freeing or

purging with inert gas shall be located either immediately

below deck or at a height of 1 m above the tank bottom.

V til ti d f i


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Ventilation and gas-freeing Outlet openings for gas-freeing cargo tanks are to be located as far

as possible from air/inert gas inlet openings at a height of at least 2

m above the deck. The gas/air mixtures are to be discharged vertically.

Outlet openings for gas-freeing of cargo tanks shall be so designedthat, taking into account the capacity of the fan, the exit velocity ofthe gas/air is at least 20 m/s.

On ships with inert gas systems, the free area of the vent openingsshall be so designed that an exit velocity of at least 20 m/s ismaintained if 3 cargo tanks are simultaneously purged with inertgas.

The openings for gas-freeing are to be fitted with screw-down

covers. On ships without inerting systems, the vent openings used for gas-

freeing are to be fitted with flame arresters.

The fitting of flame arresters may be dispensed with if a velocity ofat least 30 m/s in the vent openings is proven.

V til ti d f i


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Ventilation duct in- and outlets are to be fitted with protective

screens with a mesh size not exceeding 13 mm.

Overheating of the mechanical components of fans and the

creation of sparks is to be avoided by appropriate design and

by the choice of suitable materials.

The safety clearance between the fan housing and the impellershall not be less than 1/10 of the inner impeller bearing

diameter, limited to a minimum of 2 mm and is to be such as

to preclude any contact

between the housing and the rotor. The maximum clearance need not to be more than 13 mm.

The above requirement also applies to portable fans.

Electric motors are to be located outside the vent ducts.

V til ti d f i


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Venting of cargo tanks:

Openings in cargo tanks are to be so located and arrangedthat no ignitable gas mixtures can be formed in closed spacescontaining sources of ignition or in the vicinity of sources ofignition on deck.

The venting of cargo tanks may be effected only through

approved pressure/vacuum relief devices which fulfil thefollowing functions:

Passage of large air or gas volumes during cargoloading/unloading and ballast operations, and

The flow of small volumes of air or gas during the voyage. Venting arrangements may be fitted individually on each tank

or may be connected to a common header system or to theinert gas system.

V til ti d f i


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Where the venting arrangements of more than one tank areconnected to a vent header system, a shut-off device is to be

provided at each tank.

Where stop valves are used, they shall be provided withlocking arrangements.

When shut-off devices according are provided, cargo tanks are

to be protected against excessive positive and negativepressures caused by thermal variations by means ofPressure/vacuum relief devices.

Venting arrangements are to be connected to the top of each

cargo tank in such a way that, under normal conditions of trimand list, they are self-draining into the cargo tanks.

Where a self-draining arrangement is impossible, permanentlyinstalled means for draining the vent lines to a cargo tank shall

be provided.

V til ti d f i


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Where flammable liquids with a flash point of 60 C or below

are carried, the in- and outlet openings of venting systems are

to be fitted with approved flame arresters.

Vents for the discharge of large volumes of air or gas during

cargo and ballast handling operations are to be designed in

accordance with the following principles: Depending on the height of the vents, these shall allow the

free flow of vapour mixtures or achieve a minimum velocity

of 30 m/s.

The vapour mixtures are to be discharged vertically upwards.The clear section of vents shall be designed in accordance

with the maximum loading rate taking into account a gas

evolution factor of 1.25.

V til ti d f i


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Cargo tanks are to be provided with a high level alarm

independent of the gauging device or with equivalent means to

guard against liquid rising in the venting system to a height

exceeding the design head of the cargo tanks.

Pressure and vacuum valves may be set higher during voyage

for the prevention of cargo losses than for controlled ventingduring loading.

Pressure/vacuum valves which are located in masthead risers

may be fitted with a by-pass arrangement which can be

opened during cargo operations. Indicators shall clearly show whether the by-pass valve is in

the open or closed position.

V til ti d f i


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In the design of pressure and vacuum valves and the

determination of their opening pressures attention is to be paid

to:

the maximum loading and unloading rate

the gas evolution factor

the flow resistance in the venting system and the permissible tank pressures

Where static flame arresters, e.g. Flame screens and

detonation arresters, are used, due attention is to be paid to the

fouling caused by the cargo.

Vent headers may be used as vapour return lines.

Vapour return line connections are to be fitted with shut-off

valves and blind flanges.

Precautions against electrostatic charges


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Precautions against electrostatic charges,

generation of sparks and hot surfaces

Precautions against electrostatic charges: The entire cargo piping system as well as permanently

installed equipment in the cargo area, e.g. pneumatically

operated winches, hydraulic drives and ejectors, are to be

bonded to the ship's hull. Cargo hoses, compressed air hoses, tank washing hoses or

other hoses used within cargo tanks or on deck within the

cargo tank area are to be equipped with bonding arrangements

over their entire length including the couplings.

Means are to be provided for the earthing of portable

ventilators to the ship's hull prior to use.



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Precautions against sparks from engine and boilerexhausts:

Outlets of exhaust gas lines from main/auxiliary engines andfrom boilers and other burner equipment shall be located at asufficient height above deck.

The horizontal distance to the cargo area shall not be less than10 m.

This distance may be reduced to 5 m provided that approvedspark arresters for internal combustion engine and spark trapsfor boiler/other burner equipment exhaust gas lines are fitted.

Protection against hot surfaces:

On oil tankers, the steam and heating media temperatures shallnot exceed 220 C.



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Gas detecting equipment: Gas detectors are to be carried on board as follows:

Two instruments each for;

flammable vapours

toxic vapours, where applicable

oxygen; are to be carried.

Cargo tanks are to be fitted with connections for measuring the

tank atmosphere.


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Inerting of double hull spaces

On oil tankers, required to be fitted with inert gas systems,suitable connections for the supply of inert gas shall be

provided on double hull spaces.

Where necessary, fixed purge pipes arranged such to take into

account the configuration of these spaces shall be fitted. Where such spaces are connected to a permanently fitted inert

gas distribution system, suitable means (e.g. a second water

seal and check valve) shall be provided to prevent cargo

vapours entering the double hull space. Where no permanent distribution system is installed, a

sufficient number of means for connecting to these spaces shall

be provided on the inert gas main.


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Ventilation of spaces in the cargo area

Cargo and ballast pump spaces are to be equipped withmechanical ventilation systems of extraction type capable of at

least 20 changes of air per hour.

The air intakes and outlets are to be located as far away from

each other as possible to prevent recirculation of dangerouscargo vapours.

The air intakes and outlets are to be located at a horizontal

distance of at least 3 metres from openings of accommodation

areas, service and machinery spaces, control stations and otherspaces outside the cargo area.

The height of the air intakes and outlets above the weather

deck shall be at least 3 metres.


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Ventilation of spaces in the cargo area

Air outlets are to be located at a height of 2 m above thegangway, where the distance between the outlets and this

gangway is less than 3m.

Suitable portable instruments for measuring oxygen and

flammable vapours shall be provided. Where measurement in double hull spaces cannot be carried

out reliably using flexible sampling hoses, fixed sampling

pipelines adapted to the configuration of these spaces shall be

provided. Materials and dimensions of the fixed lines shall be such as to

prevent any restriction of their function.

Plastic pipes shall be electrically conductive.


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Safety equipment in cargo pump rooms

Temperature sensing devices shall be fitted on cargo, ballast andstripping pump casings, bearings and on their gastight bulkheadshaft glands.

Visible and audible alarms shall be effected in the cargo controlroom or the pump control station.

Pump room lighting, except emergency lighting, shall be interlockedwith the ventilation such that lighting can only be switched on whenthe ventilation is in operation.

Failure of the ventilation shall not cause the lighting to go out.

A system for continuous monitoring of the concentration offlammable vapours shall be fitted.

Sequential sampling is acceptable, if dedicated to the pump roomsampling points only and the sampling time is reasonably short.


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Safety equipment in cargo pump rooms

Sampling points or detector heads shall be fitted in suitablelocations, e.g. in the exhaust ventilation duct and in the lower

part of the pump room above the floor plates, so that any

possible leakage may be readily detected.


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Machinery spaces

Machinery spaces shall be positioned aft of cargo tanks andslop tanks; they shall also be situated aft of cargo pump roomsand cofferdams, but not necessarily aft of the oil fuel bunkertanks.

Any machinery space shall be isolated from cargo tanks andslop tanks by cofferdams, cargo pump rooms, oil fuel bunkertanks or ballast tanks.

Pump-rooms containing pumps and their accessories forballasting those spaces situated adjacent to cargo tanks and

slop tanks and pumps for oil fuel transfer shall be consideredas equivalent to a cargo pump-room within the context of thisregulation, provided that such pump-rooms have the samesafety standard as that required for cargo pump-rooms.


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Machinery spaces

However, the lower portion of the pump-room may be recessedinto machinery spaces of category A to accommodate pumps

provided that the deck head of the recess is in general not more

than one third of the moulded depth above the keel.

If the size of the vessel do not exceed 25000 tonnesdeadweight, and where it can be demonstrated that for reasons

of access and satisfactory piping arrangements this is

impracticable, the Administration may permit a recess of more

height, but not exceeding one half of the moulded depth abovethe keel.


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Accommodation spaces

Accommodation spaces, main cargo control stations, control stationsand service spaces (excluding isolated cargo handling gear lockers)

shall be positioned aft of all cargo tanks, slop tanks, and spaces

which isolate cargo or slop tanks from machinery spaces but not

necessarily aft of the oil fuel bunker tanks and ballast tanks, but

shall be arranged in such a way that a single failure of a deck or

bulkhead shall not permit the entry of gas or fumes from the cargo

tanks into an accommodation space, main cargo control stations,

control station, or service spaces.

A recess provided in the pump room need not be taken into accountwhen the position of these spaces is being determined.


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Accommodation spaces

Where the fitting of a navigation position above the cargo area isshown to be necessary, it shall be for navigation purposes only, and

it shall be separated from the cargo tank deck by means of an open

space with a height of at least 2 m.

Deck spills shall be kept away from accommodation and service

areas and from discharge into the sea by a permanent continuous

coaming of minimum 100 mm high surrounding the cargo deck.

Scupper plugs of mechanical type are required.

Means of draining or removing oil or oily water within the coamings

shall be provided.

L ti d ti f


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Location and separation of spaces No cargo, wastes or other goods should be contained in

cofferdams.


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Segregated Ballast Tanks

Segregated ballast tanks have become compulsory for all crude oiltankers of 20000tons and above, and for all product carriers of

30000tons and above those are built on or after 31/12/1979.

The capacity should be at least such that with just the segregated

ballast plus the light ship weight , the vessel will be able to meet

each of the following criteria:-

1. The amidships draft should be at least 2.0 + 0.02 L.

2. The forward and aft drafts should correspond to the amidshipsdraft above with a stern trim not more than 0.015L.

3. In any case , the propeller must be fully immersed.

During heavy weather if required the ballast can be taken in cargo

tanks.


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In no case shall ballast water be carried in cargo tanks, except:1. Of an oil tanker on those rare voyages when weather conditions

are so severe that, in the opinion of the master, it is necessary to

carry additional ballast water in cargo tanks for the safety of the

ship; and

2. In exceptional cases where the particular character of the operation

enders it necessary to carry ballast water in excess of the quantity

required as per this regulation, provided that such operation of the

oil tanker falls under the category of exceptional cases as

established by the Organization.

Slop Tanks


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Slop Tanks

Slop Tanks: MARPOL Annex-1 Regulation-29

Oil tankers of 150 gross tons and above must be provided with sloptanks.

For ships built before 31st December 1979, any cargo tank may be

designated as slop tank.

Adequate means shall be provided for cleaning the cargo tanks andtransferring the dirty ballast residue and tank washings from the

cargo tanks into a slop tank approved by the Administration.

The arrangement of slop tank shall have a capacity necessary to

retain the slop generated by tank washings, oil residues or dirtyballast residues and the total capacity shall not be less than 3% of

the oil carrying capacity.

Slop Tanks


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Slop Tanks

The above capacity may be reduced as follows:

1. 2% for such oil tankers where the tank washing arrangements aresuch that once the slop tank or tanks are charged with washing

water, this water is sufficient for tank washing and, where

applicable, for providing the driving fluid for eductors, without the

introduction of additional water into the system;

2. 2% where segregated ballast tanks or dedicated clean ballast tanks

are provided, or where a cargo tank cleaning system using crude

oil washing is fitted.

3. This capacity may be further reduced to 1.5% for such oil tankers

where the tank washing arrangements are such that once the slop

tank or tanks are charged with washing water, this water is

sufficient for tank washing and, where applicable, for providing

the driving fluid for eductors, without the introduction of

additional water into the system; and

Slop Tanks


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Slop Tanks

4. 1% for combination carriers where oil cargo is only carried in

tanks with smooth walls.5. This capacity may be further reduced to 0.8% where the tank

washing arrangements are such that once the slop tank or tanks are

charged with washing water, this water is sufficient for tank

washing and, where applicable, for providing the driving fluid for

eductors, without the introduction of additional water into the

system.

Slop tanks shall be so designed, particularly in respect of the

position of inlets, outlets, baffles or weirs where fitted, so as to

avoid excessive turbulence and entrainment of oil or emulsion withthe water.

Slop tanks of oil tankers of 70000 tonnes deadweight and above

shall be provided with at least 2 slop tank.


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Pump-room bottom protection-Reg.22

This regulation applies to oil tankers of 5,000 tonnes deadweight

and above constructed on or after 1 January 2007.

The pump-room shall be provided with a double bottom such that at

any cross-section the depth of each double bottom tank or space

shall be such that the distance h between the bottom of the pump-

room and the ship's baseline measured at right angles to the ship'sbaseline is not less than specified below:

h =B/15 (m) orh = 2 m, whichever is the lesser and but in case

h>1m.

P b tt t ti R 22


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Pump-room bottom protection-Reg.22

In case of pump-rooms whose bottom plate is located above the

baseline by at least the minimum height required in aboveparagraph, there will be no need for a double bottom construction in

way of the pump-room.

Ballast pumps shall be provided with suitable arrangements to

ensure efficient suction from double bottom tanks. If the flooding of the pump-room would not render the ballast or

cargo pumping system inoperative, a double bottom need not be

fitted.

Access to Accommodation


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Arrangement of Access and Openings to Spaces and Tanks:

Accommodation and non-hazardous spaces: Entrances, air inlets and openings to accommodation spaces, service

spaces, control stations and machinery spaces shall not face the

cargo area.

They shall be located on the end bulkhead and or on the outboardside of the superstructure or deckhouse at a distance of at least L/25

but not less than 3 m from the end of the superstructure or

deckhouse facing the cargo area.

This distance, however, need not exceed 5 m.



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Within the limits specified above, the following apply:

Bolted plates for removal of machinery may be fitted. Such plates shall be insulated to A-60 class standard.

Signboards giving instruction that the plates shall be kept closed

unless the ship is gas-free, shall be posted on board.

Wheelhouse windows may be non-fixed and wheelhouse doors maybe located within the above limits as long as they are so designed

that a rapid and efficient gas and vapour tightening of the

wheelhouse can be ensured.

Windows and side scuttles shall be of the fixed (non-opening) type. Such windows and side scuttles except wheelhouse windows, shall

be constructed to A-60 class standard.

Accommodation Spaces


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'A' Class Divisions

'A' class divisions are bulkheads and decks constructed of steel or

other equivalent material, capable of preventing the passage of

smoke and flame to the end of the one-hour standard fire test.

They are insulated with approved materials such that the average

temperature of the unexposed side will not rise more than 139oC

above the original temperature, nor will the temperature at any

one point, including any joint, rise more than 180oC above the

original temperature, within the time listed below:

Class "A-60" 60 minutes Class "A-30" 30 minutes

Class "A-15" 15 minutes

Class "A-0" 0 minutes



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'B' Class Divisions

'B' Class divisions are bulkheads, decks, ceilings and linings

constructed of approved non-combustible materials, capable of

preventing the passage of flame to the end of the first half-hour

of the standard fire test.

They have an insulation value such that the average temperature

of the unexposed side will not rise more than 139oC above the

original temperature, nor will the temperature at any one point,

including any joint, rise more than 225oC above the original

temperature, within the time listed below :

Class "B-15" 15 minutes

Class "B-0" 0 minutes



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'C' Class Divisions

'C' Class divisions are bulkheads, decks, ceilings and linings

constructed of approved non-combustible materials, which

have no requirements relative to the passage of smoke and

flame nor the limiting of temperature rise.



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All external openings are to be kept closed when a tanker cargo

operations is underway. Ventilation inlets for the spaces are to be located as far as

practicable from gas dangerous zones.

Also to prevent the entry of the cargo vapour in to the

accommodation spaces and engine room spaces, these areas are keptpressurized by suitably arranging the ventilation.

Crure Oil Washing Arrangements


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Crude oil carriers of 20 000 tons deadweight and above shall be

fitted with a crude oil washing arrangement complying with

MARPOL 73/78 Annex I, Reg. 33 and Reg. 35.

Crude oil carriers (Tanker for Oil) less than 20 000 tons deadweight,

fitted with a crude oil washing arrangement complying with design

requirements in the specifications , may be assigned the special

feature notation COW.

The advantage of doing COW is two fold:

1. It reduces the ROB after discharging by 60% and thus more cargo

is discharged to the buyer. For VLCCs this quantity can go upto

1000tons.

2. Since more quantity of cargo is discharged at the discharge port,

more quantity of cargo can be loaded in the loading port and thus

increases the earning capacity of the vessel.



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Apart from these financial benefits the pollution during ballast

water discharge is reduced after the tank cleaning.

Tank cleaning becomes more easier and faster as only a light

water wash all that is necessary after the crude oil washing.

Hence the preparation for dry docking becomes easier.

As the water washing is reduced the related tank corrosionproblems are reduced to some extend.

The disadvantages associated with COW are:

1. Extended berth occupancy

2. Additional crew requirements3. Huge cost of equipments

4. Increased safety requirement during COW.

5. Increased fuel consumption.



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The heavy weather ballast tanks are to be kept crude oil washed at

all times.

Normally 25% of the remaining cargo tanks are crude oil washed,

so that over a period of 4 discharge operations all the cargo tanks

will be crude oil washed, which makes sludge control more easy.

But in the past it shown that all the disadvantages are offset bydoing the COW, with regard to environmental pollution.

With the world oil reserves diminishing at a very fast rate, it is

worthwhile to take the additional burden of all the stated

disadvantages.

Electrical Installations


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Insulation monitoring

I nsulation fault. Device(s) to continuously monitoring theinsulation earth shall be installed for both insulated and

earthed distribution systems.

An audible and visual alarm shall be given at a manned

position in the event of an abnormally low level of insulationresistance and or high level of leakage current.

Electrical equipment and wiring are in general not to be

installed in hazardous areas.

Where essential for operational purposes, arrangement of

electrical installations in hazardous areas are to the satisfaction

of the administrations.



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Area classification is a method of analyzing and classifying the

areas where explosive gas atmospheres may occur. The object of the classification is to allow the selection of

electrical apparatus able to be operated safely in these areas.

In order to facilitate the selection of appropriate electrical

apparatus an the design of suitable electrical installations,hazardous areas are divided into zones 0, 1 and 2 according to

the principles of the standards of International Electro-

technical Commission(IEC).

A space with opening to an adjacent hazardous area on opendeck, may be made into a less hazardous or non-hazardous

space, by means of overpressure.

Oil Tanker Construction Rules

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