15.8.1 Propylene oxide transported under the provisions of this section should be
15.8.2 Unless cargo tanks are properly cleaned, these products should not be carried in
tanks which have contained as one of the three previous cargoes any products known to
catalyse polymerization, such as:
.1 mineral acids (e.g. sulphuric, hydrochloric, nitric);
.2 carboxylic acids and anhydrides (e.g. formic, acetic);
.3 halogenated carboxylic acids (e.g. chloracetic);
.4 sulphonic acids (e.g. benzene sulphonic);
.5 caustic alkalis (e.g. sodium hydroxide, potassium hydroxide);
.6 ammonia and ammonia solutions;
.7 amines and amine solutions;
.8 oxidizing substances.
15.8.3 Before loading, tanks should be thoroughly and effectively cleaned, to remove all
traces of previous cargoes from tanks and associated pipework, except where the
immediately prior cargo has been propylene oxide or ethylene oxide / propylene oxide
mixtures. Particular care should be taken in the case of ammonia in tanks made of steel
other than stainless steel.
15.8.4 In all cases, the effectiveness of cleaning procedures for tanks and associated
pipework should be checked by suitable testing or inspection, to ascertain that no traces of
acidic or alkaline materials remain that might create a hazardous situation in the presence
of these products.
15.8.5 Tanks should be entered and inspected prior to each initial loading of these
products to ensure freedom from contamination, heavy rust deposits and visible structural
defects. When cargo tanks are in continuous service for these products, such inspections
should be performed at intervals of not more than two years.
15.8.6 Tanks for the carriage of these products should be of steel or stainless steel
Suitable tank coatings may be accepted as such by the administration and noted on the
international certificated of fitness for the carriage of Dangerous chemicals in Bulk.
15.8.7 Tanks for the carriage of these products may be used for other cargoes after
thorough cleaning of tanks and associated pipework systems by washing or purging.
15.8.8 All valves, flanges, fittings and accessory equipment should be of type suitable for
use with the products and should be constructed of steel or stainless steel in accordance
with recognized standards. Discs or disc faces, seats and other wearing parts of valves
should be made of stainless steel containing not less than 11% chromium.
15.8.9 Gaskets should be constructed of materials which do not react with, dissolve in, or
lower the auto-ignition temperature of, these products and which are fire resistant and
possess adequate mechanical behaviour. The surface presented to the cargo should be
polytetrafluoroethylene (PTFE), or materials giving a similar degree of safety by their
inertness. Spirally-wound stainless steel, with a filler of PTFE of similar fluorinated
polymer, may be accepted.
15.8.10 Insulation and packing, if used, should be of a material which does not react
with, dissolve in, or lower the auto-ignition temperature of, these products.
15.8.11 The following materials are generally found unsatisfactory for gaskets, packing
and similar uses in containment systems for these products and would require testing
before being approved by the Administration:
.1 Neoprene or natural rubber, if it comes into contact with the products.
.2 Asbestos, or binders used with asbestos.
.3 Materials containing oxides of magnesium, such as mineral wools.
15.8.12 Threaded joints should not be permitted in the cargo liquid and vapour lines.
15.8.13 Filling and discharge piping should extend to within 100 mm of the bottom of
the tank or any sump pit.
15.8.14 The containment system for a tank containing these products should have a
valved return connection.
15.8.15 The products should be loaded and discharged in such a manner that venting of
the tanks to atmosphere does not occur. If vapour return to shore is used during tank
loading, the vapour return system connected to a containment system for the product
should be independent of all other containment systems.
15.8.16 During discharging operations, the pressure in the cargo tank must be maintained
above 0.07 bar gauge.
15.8.17 Tanks carrying porpylene oxide should be vented independently of tanks carrying
other products. Facilities should be provided for sampling the tank contents without
opening the tank to atmosphere.
15.8.18 The cargo should be discharged only by deepwell pumps, hydraulically operated
submerged pumps, or inert gas displacement. Each cargo pump should be arranged to
ensure that the product does not heat significantly if the discharge line from the pump is
shut off or otherwise blocked.
15.8.19 Cargo hoses used for transfer of these products should be marked "FOR
ALKYLENE OXIDE TRANSFER ONLY".
15.8.20 Cargo tanks, void spaces and other enclosed spaces, adjacent to an integral
gravity cargo tank carrying propylene oxide, should either contain a compatible cargo
(those cargoes specified in 15.8.2 are examples of substances considered incompatible) or
be inerted by injection of a suitable inert gas. Any hold space in which an independent
cargo tank is located should be inerted. Such inerted spaces and tanks should be monitored
for these products and oxygen. The oxygen content of these spaces should be maintained
below 2 per cent.
15.8.21 In no case should air be allowed to enter the cargo pump or piping system while
these products are contained within the system.
15.8.22 Prior to disconnecting shore-lines, the pressure in liquid and vapour lines should
be relieved through suitable valves installed at the loading header. Liquid and vapour from
these lines should not be discharged to atmosphere.
15.8.23 Propylene oxide may be carried in pressure tanks or in independent or integral
gravity tanks. Ethylene oxide / propylene oxide mixtures should be carried in independent
gravity tanks or pressure tanks. Tanks should be designed for the maximum pressure
expected to be encountered during loading, conveying and discharging cargo.
15.8.24 carriage Tank with a design pressure less than 0.6 bar gauge and tanks for the
carriage of ethylene oxide / propylene oxide mixtures with a design pressure less than 1.2
bar gauge should have a cooling system to maintain the cargo below the reference
temperature. Reference temperature(R) means, in the case of propylene oxide, the
temperature corresponding to the vapour pressure of the propylene oxide at the set pressure
of the pressure relief valve.
15.8.25 The refrigeration requirement for tanks with a design pressure less than 0.6 bar
gauge may be waived by the Administration for ships operating in restricted areas or on
voyages of restricted duration, and account may be taken in such cases of any insulation
of the tanks. The area and times of year for which such carriage would be permitted
should be included in the conditions of carriage of the International Certificate of Fitness
for the Carriage of Dangerous Chemicals in Bulk.
15.8.26 Any cooling system should maintain the liquid temperature below the boiling
temperature at the containment pressure. At least two complete cooling plants automatically
regulated by variations within the tanks should be provided. Each cooling plant should be
complete with the necessary auxiliaries for proper operation. The control system should
also be capable of being manually operated. An alarm should be provided to indicate
malfunctioning of the temperature controls. The capacity of each cooling system should be
sufficient to maintain the temperature of the liquid cargo below the reference temperature
of the liquid cargo below the reference temperature(R).
15.8.27 An alternative arrangement may consist of three cooling plants, any two of which
should be sufficient to maintain the liquid temperature below the reference temperature(R).
15.8.28 Cooling media which are separated from the products by a single wall only
should be non-reactive with the products.
15.8.29 Cooling systems requiring compression of the products should not be used.
15.8.30 Pressure relief valve settings should not be less than 0.2 bar gauge, or greater
than 0.7 bar gauge, for pressure tanks.
15.8.31 The piping system for tanks to be loaded with these products should be separated
(as defined in 1.3.24) from piping systems for all other tanks, including empty tanks. If
the piping system for the tanks to be loaded is not independent (as defined in 1.3.15), the
required piping separation should be accomplished by the removal of spool pieces, valves,
or other pipe sections, and the installation of blank flanges at these locations. The required
separation applies to all liquid and vapour piping, liquid and vapour vent lines and any
other possible connections, such as common inert gas supply lines.
15.8.32 These products may be transported only in accordance with cargo handling plans
that have been approved by the Administration. Each intended loading arrangement should
be shown on a separate cargo handling plan. Cargo handling plans should show the entire
cargo piping system and the locations for installation of blank flanges needed to meet the
above piping separation requirements. A copy of each approved cargo handling plan should
be maintained on board the ship. The International Certificate of Fitness for the Carriage
of Dangerous Chemicals in Bulk should be endorsed to include reference to the approved
cargo handling plans.
15.8.33 Before each initial loading of these products and before every subsequent return
to such service, certification verifying that the required piping separation has been achieved
should be obtained from a responsible person acceptable to the Port Administration and
carried on board the ship. Each connection between a blank flange and a pipeline flange
should be fitted with a wire and seal by the responsible person to ensure that inadvertent
removal of the blank flange is impossible.
18.104.22.168 No cargo tanks should be more than 98 per cent liquid full at the reference
22.214.171.124 The maximum volume to which a cargo tank should be loaded (VL) should be:
126.96.36.199 The maximum allowable tank filling limits for each cargo tank should be
indicated for each loading temperature which may be applied, and for the applicable
maximum reference temperature, on a list to be approved by the Administration. A copy
of the list should be permanently kept on board by the master.
15.8.35 The cargo should be carried under a suitable protective padding of nitrogen gas.
An automatic nitrogen make-up system should be installed to prevent the tank pressure
falling below 0.07 bar gauge in the event of product temperature fall due to ambient
conditions or maloperation of refrigeration systems. Sufficient nitrogen should be available
on board to satisfy the demand of the automatic pressure control. Nitrogen of commercially
pure quality (99.9 per cent by volume) should be used for padding. A battery of nitrogen
bottles connected to the cargo tanks through a pressure reduction valve satisfies the
intention of the expression "automatic" in this context.
15.8.36 The cargo tank vapour space should be tested prior to and after loading to ensure
that the oxygen content is 2% by volume or less.
15.8.37 A water spray system of sufficient capacity should be provided to blanket
effectively the area surrounding the loading manifold, the exposed deck piping associated
with product handling, and the tank domes. The arrangement of piping and nozzles should
be such as to give a uniform distribution rate of 10 l/㎡ min. Remote manual operation
should be arranged such that remote starting of pumps supplying the water spray system
and remote operation of any normally closed valves in the system can be carried out from
a suitable location outside the cargo area, adjacent to the accommodation spaces and
readily accessible and operable in the even of fire in the areas protected. The water spray
system should be capable of both local and remote manual operation, and the arrangement
should ensure that any spilled cargo is washed away. Additionally, a water hose with
pressure to the nozzle, when atmospheric temperatures permit, should be connected ready
for immediate use during loading and unloading operations.
15.8.38 A remotely operated, controlled closing-rate, shut-off valve should be provided at
each cargo hose connection used during cargo transfer.