Iranian Classification Society Rules

ᾬ Ņ ᾬLN ÜᾟÑÌ Ń

ᾟ Üᾟ Ň Ì

where:

ᾬL = maximum working pressure of the inner pipe

ᾟ = Cp/Cv constant pressure specific heat divided by the constant volume specific heat(1.31 for CH4)

The tangential membrane stress of a straight pipe is not to exceed the tensile strength div- ided by 1.5 (Rm/1.5) when subjected to the above pressures. The pressure ratings of all oth- er piping components are to reflect the same level of strength as straight pipes. As an alter- native to using the peak pressure from the above formula, the peak pressure found from representative tests can be used. Test reports are then to be submitted.

(4) For low pressure piping, the duct is to be dimensioned for a design pressure not less than the maximum working pressure of the FC fuel pipes. The duct is also to be pressure tested to show that it can withstand the expected maximum pressure at gas pipe rupture.

3. Fuel supply system for ESD-protected FC spaces is to comply with the following.

(1) The pressure in the FC fuel supply system is not to exceed 1.0 MPa.

(2) The FC fuel supply lines are to have a design pressure not less than 1.0 MPa.

108. FC fuel storage

1. Liquefied gas storage tanks

(1) The storage tank used for liquefied gas is to be an independent tank(type C) designed in ac- cordance with the Rules for Steel Ships Pt. 7 Ch. 5 , Sec. 4.

(2) Pipe connections to the tank are normally to be mounted above the highest liquid level in the tanks. However, connections below the highest liquid level may be accepted after special consid- eration by the Society, but will not accepted for liquid hydrogen tanks located in enclosed spaces.

(3) Pressure relief valves as required in the Rules for Steel Ships Pt. 7 Ch. 5 , Sec. 8. are to be

fitted.

(4)

(5)

The outlet from the pressure relief valves is normally to be located at least B/3 or 6 m, whichever is greater, above the weather deck and 6 m above the working area and gangways.

The outlets are normally to be located at least 10 m from the nearest:

(A) Air intake, air outlet or opening to accommodation, service and control spaces, or other gas safe spaces; and

(B) Exhaust outlet from machinery or from furnace

installation.

Storage tanks for liquid gas are not to be filled to more than 98% full at the reference temper- ature, where the reference temperature is as defined in the Rules for Steel Ships Pt. 7 Ch. 5, paragraph 1501. 4. A filling limit curve for actual filling temperatures is to be prepared from the formula given in the Rules for Steel Ships Pt. 7 Ch. 5, paragraph 1501. 2. However, when the tank insulation and tank location makes the probability very small for the tank con- tents to be heated up due to external fire, special considerations may be made to allow a high-

(6) er filling limit than calculated using the reference temperature, but never above 95%.

Means that are not dependent on the FC fuel system are to be provided whereby liquid gas in

(7) the storage tanks can be emptied.

It is to be possible to empty, purge gas and vent FC fuel tanks with gas piping systems. Procedures are to be prepared for this. Inerting is to be performed with, for instance, nitrogen,

CO2 or argon prior to venting to avoid an explosion hazardous atmosphere in tanks and gas

(8) pipes.

In case of liquid hydrogen storage, the inner pressure vessel must be designed to operate at a

temperature of -253°C. Filling piping and piping before a vaporizer must also be designed to these temperatures. The rest of the system must be designed to accept temperatures likely to be

(9) encountered after installation in the ship.

Storage tanks for liquid gas with vapour pressure above the design pressure at 45ºC are to be

2. Compressed gas storage tanks

(1) The storage tanks to be used for compressed gas are to be certified and approved by the Society.

(2) Tanks for compressed gas are to be fitted with pressure relief valves with a set point below the design pressure of the tank and with outlet located as required in 1.(4).

3. Storage on open deck

(1) Both gases of the compressed and the liquefied type may be accepted stored on open deck.

(2) The storage tanks or tank batteries are to be located at least B/5 from the ship's side. For ships other than passenger ships a tank location closer than B/5 but not less than 760 mm from the ship's side may be accepted.

(3) The gas storage tanks or tank batteries and equipment are to be located to assure sufficient nat- ural ventilation, so as to prevent accumulation of escaped gas.

(4) Tanks for liquid gas with a connection below the highest liquid level (See 1.(2) ) are to be

fitted with drip trays below the tank which are to be of sufficient capacity to contain the vol- ume which could escape in the event of a pipe connection failure. The material of the drip tray is to be stainless steel, and there are to be efficient separation or isolation so that the hull or deck structures are not exposed to unacceptable cooling, in case of leakage of liquid gas.

4. Storage in enclosed space

(1) Gas in a liquid state may be stored in enclosed spaces, with a maximum acceptable working pressure of 1.0 MPa and below. Storage of compressed gas in enclosed spaces and location of gas tanks with a higher pressure than 1.0 MPa in enclosed spaces is normally not acceptable, but may be permitted after special consideration and approval by the Society provided the fol-

lowing is fulfilled in addition

(A) Adequate means are to can affect the tank; and

(B) All surfaces within the

to (3).

be provided to depressurize the tank in case of a fire which

tank room are to be provided with suitable thermal protection

against any lost high pressure gas and resulting condensation unless the bulkheads are de- signed for the lowest temperature that can arise from gas expansion leakage; and

(2) Hydrogen is not to be stored in enclosed spaces, unless the tilation as given in 110. 6, electrical equipment certified safe

tank room is arranged with ven- for hydrogen atmosphere, and ar-

rangement of the space and ventilation outlets as given in 103. 3. (4).

(3) The gas storage tank(s) are to be placed as close as possible to the center ships other than passenger ships and multi-hulls, a tank location closer than ship side may be accepted:

(A) Minimum, the lesser of B/5 and 11.5m from the ship side;

(B) Minimum, the lesser of B/15 and 2m from the bottom plating;

line. But, B/5 from

for the

(4)

The storage tank and associated valves and piping are to be located in a space

designed to

act as a second barrier, in case of liquid or compressed gas leakage. The material of the bulk-

heads of this space is to have the same design temperature as the gas tank, and the space is to be designed to withstand the maximum pressure build-up. Alternatively, pressure relief venting

to a safe location (mast) can be provided. The space is to be capable of containing leakage, and is to be isolated thermally so that the surrounding hull is not exposed to unacceptable cool-

ing, in case of leakage of the liquid or compressed gas. This second barrier space is in other parts of these Guidance called "tank room". When the tank is double walled and the outer tank

shell is made of cold resistant material, a tank room could be arranged as a box fully welded

to the outer shell of the tank, covering all tank connections and valves, but not necessarily all of the outer tank shell.

(5) The tank room may be accepted as the outer shell of a stainless steel vacuum insulated tank in combination with a stainless steel box welded to the outer shell, containing all tank pipe con- nections, valves, piping, etc. In this case, the requirements for ventilation and gas detection are to be made applicable to the box, but not to the double barrier of the tank.

(6)

Bilge suctions from the tank room, if provided, are not to be connected to the bilge system for the rest of the ship.

109. FC fuel bunkering system and distribution system outside machinery spaces

1. FC fuel bunkering station

(1) The FC fuel bunkering station is to be so located that sufficient natural ventilation is provided.

Closed or semi-enclosed bunkering stations are to be subject to special consideration. The bun- kering station is to be physically separated or structurally shielded from accommodation, car- go/working deck and control stations. Connections and piping are to be so positioned and ar- ranged that any damage to the fuel piping does not cause damage to the vessel’s fuel storage tank arrangement leading to uncontrolled gas discharge.

(2) Drip trays are to be fitted below liquid gas bunkering connections and where leakage may occur. The drip trays are to be made of stainless steel, and are to be drained over the ship's side by a pipe that preferably leads down near the sea. This pipe could be temporarily fitted

for bunkering operations. The surrounding hull or deck structures are not to be exposed to un- acceptable cooling, in case of leakage of liquid gas. For compressed gas bunkering stations, low

(3)

temperature steel shielding are to be provided to prevent the possible escape of

pinging on surrounding hull structure.

Control of the bunkering is to be possible from a safe location in regard operations. At this location tank pressure and tank level are to be monitored.

cold jets im-

to bunkering Over-pressure

alarm, overfill alarm and automatic shutdown are also to be indicated at this location.

2. FC fuel bunkering system

(1)

The bunkering system is to be so arranged that no gas is discharged to air during storage tanks.

filling of

(2) A manually-operated stop valve and a remote operated shutdown valve in series, or a

manually-operated and remote valve are to be fitted in every bunkering line close to

combined

the shore

connecting point. It is to be possible to release the remote-operated valve in the control location

for bunkering operations or another safe location.

(3) If the ventilation in the ducting around the FC fuel bunkering lines stops, an audible and visual alarm is to be provided at bunkering control location.

(4) If gas is detected in the ducting around the bunkering lines, an audible and visual alarm is to be provided at the bunkering control location.

(5)

(6)

Means are to be provided for draining the liquid from the bunkering pipes at bunkering

completion.

Bunkering lines are to be arranged for inerting and gas freeing. During operation of the vessel, the bunkering pipes are to be gas free.

3. Distribution outside of machinery spaces

(1) FC fuel piping is stations.

(2) Hydrogen pipes are

hydrogen pipes may

not to be led through accommodation spaces, service spaces or control

not to be led through enclosed spaces other than the FC spaces. However, be considered accepted led through other spaces if these spaces are defined

(3)

as gas hazardous(e.g. all equipment inside are spark proof and certified safe for hydrogen at-

mosphere). Such spaces must have a simple geometrical shape, and are to be arranged with a ventilation system and rate as required for FC fuel spaces with open hydrogen pipes, and the space.

Where gas pipes pass through enclosed spaces in the ship, they are to be enclosed in a duct. This duct is to be mechanically under pressure ventilated with 30 air changes per hour, and gas

detection as required in 110. 5. is to be provided.

(4) The duct is to be dimensioned according to 107. 2.(3) and (4).

(5)

(6)

(7)

The ventilation inlet for the duct is to always be located in open air, away from ignition sources.

Gas pipes located in open air are to be so located that they are not likely to be damaged by accidental mechanical impact.

High-pressure gas lines outside the FC spaces are to be installed and protected so as to mini-

mize the risk of injury to personnel in case of rupture.

110. Ventilation system

1. General

(1) Spaces in which there is a risk that an ignitable gas mixture may be formed by FC fuel are to be equipped with mechanical ventilation systems of the extraction type capable of being con- trolled from outside such spaces. Provisions are to be made to ventilate such spaces prior to en- tering the compartment and operating the equipment and a warning notice requiring the use of such ventilation are to be placed outside the compartment.

(2) Any ducting used for the ventilation of hazardous spaces caused by the FC installation is not to serve any other spaces and be separate from that used for the ventilation of non-hazardous

spaces.

(3) Electric motors driving fans are to be placed outside ventilation ducts for hazardous spaces un- less the motor is certified for the same hazard zone as the space served. Electric motors driving

fans are to be placed outside ventilation ducts for spaces containing hydrogen installations.

(4) Ventilation gen release

fans serving spaces containing sources of hydrocarbon release or sources of hydro- are not to produce a source of vapour ignition in either the ventilated space or the

ventilation system associated with the space. Ventilation fans and fan ducts, in way of fans on- ly, for gas-dangerous spaces are to be of non sparking construction defined as:

(A) impellers or housing of nonmetallic construction, due regard being paid to the elimination

of static electricity;

(B) impellers and housing of nonferrous materials;

(D) ferrous impellers and housing with not less than 13 mm design tip clearance.

Any combination of an aluminium or magnesium alloy fixed or rotating component and a fer-

rous fixed or rotating component, regardless of tip clearance, is considered a sparking hazard

and is not to be used in these places.

(5) The ventilation system is to ensure a good air circulation in all spaces, and in particular ensure that there is no possibility of formation of gas pockets in the room.

(6)

(7)

(8)

For spaces containing hydrogen release sources, design for arrangements and ventilation is to be in accordance with the requirements in 6. and 103. 4.

Means are to be provided to indicate any loss of the required ventilating capacity in the

engine control station.

Air inlets for hazardous enclosed spaces are to be taken from areas which, in the absence of the considered inlet, would be non-hazardous. Air inlets for non-hazardous enclosed spaces are to be taken from non-hazardous areas at least 1.5 m away from the boundaries of any hazard- ous area.

(9) Where the inlet duct passes through a more hazardous space, the duct is to have over-pressure relative to this space, unless mechanical integrity and gas-tightness of the duct will ensure that gases will not leak into it.

(10) Air outlets from non-hazardous spaces are to be located outside hazardous areas.

(11) Air outlets from hazardous enclosed spaces are to be located in an open area which, in absence of the considered outlet, would be of the same or lesser hazard than the

lated space.

the venti-

(12) The required capacity of the ventilation system is normally based on the total volume of

the space. An increase in required ventilation capacity may be necessary for the spaces ing a complicated form.

hav-

(13) Ventilation systems in spaces with release sources from piping systems with FC fuel that is gases and vapours lighter than air are to be met the following.

(A) The spaces are to be ventilated by means of mechanically driven exhaust air fans.

(B) The supply air inlet is to be connected to the lower part of the spaces.

(C) The spaces are to be designed in such a way that gases collect at the top at central points from which they are extracted.

(D) A suction hood or a suction trunk is to be provided for areas containing flanges, valves

etc. The suction hood or suction trunk is to be arranged in such a way that the air flows around the gas-bearing components, and the air/gas mixture can be extracted at the upper part of the suction hood or trunk.

2. Non-hazardous spaces

(1) Non-hazardous spaces with opening to a hazardous area are to be arranged with an air-lock and be maintained at overpressure relative to the external hazardous area. The overpressure ven- tilation is to be arranged according to the following requirements:

(A) During initial start-up or after loss of overpressure ventilation, before energizing any elec trical installations not certified safe for the space in the absence of pressurization, it is to be required to:

(a) proceed with purging (at least 5 air changes) or confirm by measurements that the space is non-hazardous; and

(b) pressurize the space.

(B) Operation of the overpressure ventilation is to be monitored.

(a) an audible and visual alarm is to be given at a manned location; and

(b) if overpressure cannot be immediately restored, automatic or programmed disconnection of electrical installations according to a recognized standard(Refer to IEC 60092-502 Electrical Installations in Ships Tankers-Special Features, table 5.) is to be conducted.

3. Gas tank room

(1) The tank room for gas storage is to be provided with an effective mechanical forced ventilation system of the under pressure type, providing a ventilation capacity of at least 30 air changes per hour. The rate of air changes may be reduced if other adequate means of explosion pro- tection are installed. The equivalence of alternative installations is to be demonstrated by a safe- ty analysis.

(2) In addition to this para., tank rooms for hydrogen tanks are to have a ventilation rate and ar- rangement as given in 6.

(3) Approved automatic fail-safe fire dampers are to be fitted in the ventilation trunk for tank

room.

4. Fuel Cell space

(1) The ventilation system for FC space is to be independent of all other ventilation systems.

(2) ESD-protected FC spaces are to have ventilation with a capacity of at least 30 air changes per hour. The ventilation system is to ensure a good air circulation in all spaces, and in particular ensure that any formation of gas pockets in the room are detected. As an alternative, arrange- ments whereby under normal operation the machinery spaces is ventilated with at least 15 air changes an hour is acceptable provided that, if gas is detected in the machinery space, the number of air changes will automatically be increased to 30 an hour.

(3) The number and power of the ventilation fans are to be such that the capacity is not reduced by more than 50% of the total ventilation capacity, if a fan with a separate circuit from the main switchboard or emergency switchboard or a group of fans with common circuit from the main switchboard or emergency switchboard, is out of action.

(4) In addition to this para., FC space for hydrogen fuel are to have a ventilation rate and arrange- ment as given in 6.

5. Gas pump and gas compressor rooms

(1) Pump and compressor rooms are to be fitted with effective mechanical ventilation system of the under pressure type, providing a ventilation capacity of at least 30 air changes per hour.

(2) The number and power of the ventilation fans are to be such that the capacity is not reduced by more than 50%, if a fan with a separate circuit from the main switchboard or emergency

switchboard or a group of fans with common circuit from the main switchboard or emergency switchboard, is out of action.

(3)

(4)

Ventilation systems for pump and compressor rooms are to be in operation when pumps or compressors are working. Signboards to this effect shall be placed in an easily visible position near the control stand.

When the space is dependent on ventilation for its hazardous area classification, the following is to apply:

(A) During initial start-up, and after loss of ventilation, the space is to be purged (at least 5 air

changes), before connecting electrical installations which are not certified for the hazardous area classification in absence of ventilation. Warning notices to this effect are to be placed in an easily visible position near the control stand.

(B) Operation of the ventilation is to be monitored.

(a) an audible and visual alarm is to be given at a manned location;

(b) immediate action is to be taken to restore ventilation; and

(c) electrical installations are to be disconnected(Intrinsically safe equipment suitable for zone 0 is not required to be switched off. Certified flameproof lighting may have a sep- arate switch-off circuit.), if ventilation cannot be restored for an extended period. The disconnection is to be made outside the hazardous areas, and be protected against un- authorized re-connection, e.g., by lockable switches.

6. Spaces containing hydrogen piping

(1) For spaces containing hydrogen release sources, the ventilation rate is to be sufficient to avoid gas concentration in the flammable range in all leakage scenarios, including pipe rupture. This is also applicable for spaces containing fully welded hydrogen pipes.

(2) The number and power of the ventilation fans are to be such that the capacity is still 100% if

a fan with a separate circuit from the main switchboard or emergency switchboard or a group of fans with common circuit from the main switchboard or emergency switchboard, is out of action.

(3) Ventilation ducts from spaces containing hydrogen piping or release sources are to be vertical or steadily ascending and without sharp bends to avoid any possibility for gas to accumulate.

< Previous | Contents | Next >