17.18.1 Products transported under the provisions
of this section shall be acetylene-free.
17.18.2 Unless cargo tanks are properly cleaned,
these products shall not be carried in tanks that have contained as
one of the three previous cargoes any product known to catalyse polymerization,
such as:
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.1 anhydrous ammonia and ammonia solutions;
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.2 amines and amine solutions; and
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.3 oxidizing substances (e.g. chlorine).
17.18.3 Before loading, tanks shall be thoroughly
and effectively cleaned to remove all traces of previous cargoes from
tanks and associated pipework, except where the immediate prior cargo
has been propylene oxide or ethylene oxide-propylene oxide mixtures.
Particular care shall be taken in the case of ammonia in tanks made
of steel other than stainless steel.
17.18.4 In all cases, the effectiveness of cleaning
procedures for tanks and associated pipework shall 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.
17.18.5 Tanks shall be entered and inspected prior
to each initial loading of these products to ensure freedom from contamination,
heavy rust deposits and any visible structural defects. When cargo
tanks are in continuous service for these products, such inspections
shall be performed at intervals of not more than two years.
17.18.6 Tanks for the carriage of these products
shall be of steel or stainless steel construction.
17.18.7 Tanks that have contained these products
may be used for other cargoes after thorough cleaning of tanks and
associated pipework systems by washing or purging.
17.18.8 All valves, flanges, fittings and accessory
equipment shall be of a type suitable for use with these products
and shall be constructed of steel or stainless steel in accordance
with recognized standards. Disc or disc faces, seats and other wearing
parts of valves shall be made of stainless steel containing not less
than 11% chromium.
17.18.9 Gaskets shall 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 shall be
polytetrafluoroethylene (PTFE) or materials giving a similar degree
of safety by their inertness. Spirally-wound stainless steel with
a filler of PTFE or similar fluorinated polymer may be accepted, if
approved by the Administration or recognized organization acting on
its behalf.
17.18.10 Insulation and packing, if used, shall
be of a material which does not react with, dissolve in, or lower
the auto-ignition temperature of, these products.
17.18.11 The following materials are generally
found unsatisfactory for use in gaskets, packing and similar uses
in containment systems for these products and would require testing
before being approved:
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.1 neoprene or natural rubber, if it comes into
contact with the products;
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.2 asbestos or binders used with asbestos; and
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.3 materials containing oxides of magnesium, such
as mineral wools.
17.18.12 Filling and discharge piping shall extend
to within 100 mm of the bottom of the tank or any sump.
17.18.13 The products shall 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
shall be independent of all other containment systems.
17.18.14 During discharging operations, the pressure
in the cargo tank shall be maintained above 0.007 MPa gauge.
17.18.15 The cargo shall be discharged only by
deepwell pumps, hydraulically operated submerged pumps or inert gas
displacement. Each cargo pump shall be arranged to ensure that the
product does not heat significantly if the discharge line from the
pump is shut off or otherwise blocked.
17.18.16 Tanks carrying these products shall be
vented independently of tanks carrying other products. Facilities
shall be provided for sampling the tank contents without opening the
tank to atmosphere.
17.18.17 Cargo hoses used for transfer of these
products shall be marked "FOR ALKYLENE OXIDE TRANSFER ONLY".
17.18.18 Hold spaces shall be monitored for these
products. Hold spaces surrounding type A and type B independent tanks
shall also be inerted and monitored for oxygen. The oxygen content
of these spaces shall be maintained below 2% by volume. Portable sampling
equipment is satisfactory.
17.18.19 Prior to disconnecting shore lines, the
pressure in liquid and vapour lines shall be relieved through suitable
valves installed at the loading header. Liquid and vapour from these
lines shall not be discharged to atmosphere.
17.18.20 Tanks shall be designed for the maximum
pressure expected to be encountered during loading, carriage or unloading
of cargo.
17.18.21 Tanks for the carriage of propylene oxide
with a design vapour pressure of less than 0.06 MPa, and tanks for
the carriage of ethylene oxide-propylene oxide mixtures with a design
vapour pressure of less than 0.12 MPa, shall have a cooling system
to maintain the cargo below the reference temperature. The reference
temperatures are referred to in 15.1.3.
17.18.22 Pressure relief valve settings shall
not be less than 0.02 MPa gauge; and for type C independent tanks
not greater than 0.7 MPa gauge for the carriage of propylene oxide
and not greater than 0.53 MPa gauge for the carriage of ethylene oxide-propylene
oxide mixtures.
17.18.23 The piping system for tanks to be loaded
with these products shall be completely separate from piping systems
for all other tanks, including empty tanks, and from all cargo compressors.
If the piping system for the tanks to be loaded with these products
is not independent, as defined in 1.2.28, the required piping separation
shall 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.
17.18.24 The products shall be transported only
in accordance with cargo handling plans approved by the Administration.
Each intended loading arrangement shall be shown on a separate cargo
handling plan. Cargo handling plans shall show the entire cargo piping
system and the locations for installation of the blank flanges needed
to meet the above piping separation requirements. A copy of each approved
cargo handling plan shall be kept on board the ship. The International
Certificate of Fitness for the Carriage of Liquefied Gases in Bulk
shall be endorsed to include references to the approved cargo handling
plans.
17.18.25 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 shall
be obtained from a responsible person acceptable to the port Administration
and carried on board the ship. Each connection between a blank flange
and pipeline flange shall be fitted with a wire and seal by the responsible
person to ensure that inadvertent removal of the blank flange is impossible.
17.18.26 The maximum allowable loading limits
for each tank shall be indicated for each loading temperature that
may be applied, in accordance with 15.5.
17.18.27 The cargo shall be carried under a suitable
protective padding of nitrogen gas. An automatic nitrogen make-up
system shall be installed to prevent the tank pressure falling below
0.007 MPa gauge in the event of product temperature fall due to ambient
conditions or malfunctioning of refrigeration system. Sufficient nitrogen
shall be available on board to satisfy the demand of the automatic
pressure control. Nitrogen of commercially pure quality (99.9% by
volume) shall 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.
17.18.28 The cargo tank vapour space shall be
tested prior to and after loading to ensure that the oxygen content
is 2% by volume or less.
17.18.29 water-spray system of sufficient capacity
shall 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
shall be such as to give a uniform distribution rate of 10l/m2/min.
The arrangement shall ensure that any spilled cargo is washed away.
17.18.30 The water-spray system shall be capable
of local and remote manual operation in case of a fire involving the
cargo containment system. Remote manual operation shall be arranged
such that the 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 event of fire in the areas protected.
17.18.31 When ambient temperatures permit, a pressurized
water hose ready for immediate use shall be available during loading
and unloading operations, in addition to the above water-spray requirements.