17.12.1 Ethylene oxide
(a) For the carriage of ethylene oxide the requirements of 17.12.8 apply analogously, with
the additions and modification as given in this paragraph.
(b) Deck tanks should not be used for the carriage of ethylene oxide.
(c) Stainless steels types 416 and 442, as well as cast iron, should not be used in ethylene
oxide cargo containment and piping systems.
(d) Before loading, tanks should 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 ethylene oxide, propylene oxide or mixtures of these
products. Particular care should be taken in the case of ammonia in tanks made of
steel other than stainless steel.
(e) Ethylene oxide should be discharged only by deepwell pumps or inert gas
displacement. The arrangement of pumps should comply with 17.12.8(f)(iii).
(f) Ethylene oxide should be carried refrigerated only and maintained at temperatures of
less than +30°C.
(g) Pressure relief valves should be set at a pressure of not less than 5.5 kp/cm2
maximum set pressure should be specially approved by the Administration.
(h) The protective padding of nitrogen gas as required by 17.12.8(p) should be such that
the nitrogen concentration in the vapour space of the cargo tank will at no time be less
than 45% by volume.
(i) Before loading and at all times when a cargo tank contains ethylene oxide liquid or
vapour, the cargo tank should be inerted with nitrogen.
(j) The water spray system required by paragraph 17.12.8(r) and that required by Section
11.3 should operate automatically in a fire involving the cargo containment system.
(k) A jettisoning arrangement should be provided to allow the emergency discharge of
ethylene oxide in the event of uncontrollable self-reaction.
17.12.2 Methyl acetylene-propadiene mixture
(a) Methyl acetylene-propadiene mixtures should be suitably stabilized for transport.
Additionally, upper limits of temperature and pressure during refrigeration should be
specified for the mixtures.
(b) Examples of acceptable, stabilized composition limits are:
(i) Composition 1
(1) maximum methyl acetylene to propadiene molar ratio of 3 to 1;
(2) maximum combined concentration of methyl acetylene and propadiene of 65
(3) minimum combined concentration of propane, butane, and isobutane of 24
mole percent, of which at least one- third (on a molar basis) must be
butanes and one-third propane; and
(4) maximum combined concentration of propylene and butadiene of 10 mole
(ii) Composition 2
(1) maximum methyl acetylene and propadiene combined concentration of 30
(2) maximum methyl acetylene concentration of 20 mole percent;
(3) maximum propadiene concentration of 20 mole percent;
(4) maximum propylene concentration of 45 mole percent;
(5) maximum butadiene and butylenes combined concentration of 2 mole per cent;
(6) minimum saturated C4 hydrocarbon concentration of 4 mole percent; and
(7) minimum propane concentration of 25 mole percent.
(c) Other compositions may be accepted provided the stability of the mixture is
demonstrated to the satisfaction of the Administration.
(d) A ship carrying methyl acetylene-propadiene mixtures should preferably have an indirect refrigeration system as specified in 7.2.4(b). Alternatively, a ship not provided with indirect refrigeration may utilize direct vapour compression refrigeration subject to pressure and temperature limitations depending on the com position.
For the example composition given in 17.12.2(b), the following features should be provided :
(i) A vapour compressor that does not raise the temperature and pressure of the
vapour above 60°C and 17.5 kg/. gauge during its operation, and that does not
allow vapour to stagnate in the compressor while it continues to run.
(ii) Discharge piping from each compressor stage or each cylinder in the same stage
of a reciprocating compressor should have;
(1) two temperature actuated shutdown switches set to operate at 60°C or
(2) a pressure actuated shutdown switch set to operate at 17.5 kg/. or less;
(3) a safely relief valve set to relieve at 18.0 kg/. gauge or 1ess.
(iii) The relief valve required by (d)(ii)(3) of this paragraph should vent to a mast meeting 8.2.9, 8.2.10, 8.2.13 and 8.2.14 and should not relieve Into the compressor suction line.
(iv) An alarm that sounds in the cargo control station and in the navigating bridge when a high pressure switch, or a high temperature switch operates.
(e) The piping system, including the cargo refrigeration system, for tanks to be loaded with methyl acetylene-propadiene mixture should be completely separate from piping and refrigeration systems for ocher tanks. If the piping system for the tanks to be loaded with methyl acetylene-propadiene mixture is not independent, 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 vent lines and any other possible
connexions such as common inert gas supply lines.
Materials of construction and ancillary equipment such as insulation should be resistant to the
effects of high oxygen concentrations caused by condensation and enrichment at the low
temperatures attained in parts of the cargo system. Due consideration should be given to ventilation
in such areas where condensation might occur to avoid the stratification of oxygen enriched
Because high concentrations of ammonia in confined spaces can be flammable, the provisions
of Chapter X for flammable products should be applied except in zones on the open deck. Liquid
ammonia should never be sprayed into a tank containing air as there is a disk of creating a static
electrical charge which could cause ignition. To minimize the risk of stress corrosion cracking
occurring when ammonia is carried at a temperature above -20°C (vapour pressure 1.9 kp/cm2
oxygen content of the vapour space in pressure vessels and in pipelines made of carbon-manganese
steel (and other steels which require special consideration) should be reduced to the minimum
practicable before liquid ammonia is introduced. The condensate system of tanks operating at -33°C may be affected unless it has been thermally stress relieved.
(a) Cargo containment
(i) The capacity of each tank should not exceed 600 m3
and the total capacity of all
cargo tanks should not exceed 1,200 m3
(ii) The tank design vapour pressure should not be less than 13.5 kp/cm2
7.1.3 and 17.4).
(iii) Parts of tanks protruding above the upper deck should be provided with
protection against thermal radiation taking into account total engulfment by fire.
(iv) Each tank should be provided with two safety relief valves. A bursting disc of
appropriate material should be installed between the tank and the safety relief
valves. The rupture pressure of the bursting disc should be 1 kp/cm2
the opening pressure of the safety relief valve, which should be set at the design
vapour pressure of the lank but not less than 13.5 kp/cm2
. The space between the
bursting disc and the relief valve should be connected through an excess flow
valve to a pressure gauge and a gas detection system, Provisions should be
made to keep this space at or near the atmospheric pressure during normal
(v) Outlets from safety relief valves should be arranged in such a way as to
minimize the hazards on board the ship as well as to the environment. Leakage
from the relief valves should be led through the absorption plant to reduce the
gas concentration as far as possible. The relief valve exhaust line should be
arranged at the forward end of the ship to discharge outboard at deck level with
an arrangement to select either port or starboard side, with a mechanical
interlock to ensure that one line is always open.
(vi) The Administration and the Port Administration may require that chlorine is
carried in refrigerated state at a maximum pressure specified by these
(b) Cargo Piping systems
(i) Cargo discharge should be performed by means of compressed chlorine vapour
from shore. dry air or another acceptable guts or fully submerged pumps. The
pressure in the vapour space of the tank during discharging should not exceed
. Cargo discharge compressors on board ships should not be
accepted by the Administration.
(ii) The design pressure of the cargo piping system should be not less than 21 kp/cm2
. The internal diameter of the cargo pipes should not exceed 100 mm. Only pipe
bends should be accepted for compensation of pipeline thermal movement. The use of flanged points should be restricted to a minimum, and when used the
flanges should be of the welding neck type with tongue and groove.
(iii) Relief valves of the cargo piping system should discharge to the absorption plant (see also 8.2.16).
(i) The cargo tanks and cargo piping systems are to be made of steel suitable for
the cargo and for a temperature of -40°C, even if a higher transport temperature
is intended to be used.
(ii) The tanks should be thermally stress relieved. Mechanical stress relief should
not be accepted as an equivalent.
(d) Instrumentation - safety devices
(i) The ship should be provided with a chlorine absorbing plant with connections to
the cargo piping system and the cargo tanks. The absorbing plant should be
capable of neutralizing at least two per cent of the total cargo capacity at a
reasonable absorption rate.
(ii) During the gas-freeing of cargo tanks, vapours should not be discharged to the
(iii) A gas detecting system should be provided capable of monitoring chlorine
concentrations of at least 1 rpm by volume. Suction points should be located :
- near the bottom of the cargo hold spaces;
- in the pipes from the safety relief valves;
- at the outlet from the gas absorbing plant;
- at the inlet to the ventilation systems for the accommodation, service, control
and machinery spaces;
- on deck at the forward end, in the middle and at the aft end of the cargo area. (Only required to be used during cargo handling and gas-freeing operations.)
The gas detection system should be provided with audible and visual alarm with a set
point of 5 ppm.
(iv) Each cargo tank should be fitted with a high pressure alarm giving audible
alarm at a pressure equal to 10.5 kp/cm2
(e) Personnel protection
In addition to the requirements given in 17.2 the following requirements should be
(i) The enclosed space required by 17.2.4 should be easily and quickly accessible
from the open deck and accommodation and should be capable of being rapidly
closed gas-tight. Access to this space from the deck and the remainder of the
accommodation should be by means of an air-lock. The space should be so
designed as to accommodate the entire crew of the ship and be provided with a
source of uncontaminated air for a period of not less than four hours. One of the
decontamination showers required by 17.2.2 should be located near the air-lock
to the space.
(ii) A compressor and the necessary equipment for toil ling the air- bottles should
(iii) One set of oxygen therapy equipment should be carried in the space referred to
in sub-paragraph (i).
(f) Filling limits for cargo tanks
(i) The requirements of 15.1.4(b) do not apply when it is intended to carry chlorine.
(ii) The chlorine content of the gas in the vapour space of the cargo tank after loading
should be greater than 80 percent by volume.
17.12.6 Vinyl chloride
In case polymerization of vinyl chloride is prevented by addition of an inhibitor,17.10 is
applicable. In case no or insufficient inhibitor has been added, any inert gas used for the purposes
of 17.8 should contain not more oxygen than 0.1 percent. Before loading is started, inert gas
samples from the tanks and piping should be analysed. When vinyl chloride is carried, a positive
pressure should always be maintained in the tanks, also during ballast voyages between successive
17.12.7 Diethyl ether/vinyl ethyl ether
(a) The cargo should be discharged only by deepwell pumps or by hydraulically operated
submerged pumps. These pumps should be of a type designed to avoid liquid pressure
against the shaft gland.
(b) Inert gas displacement may be used for discharging cargo from independent tanks type
C provided the cargo system is designed for the expected pressure.
17.12.8Propylene oxide and mixtures of ethylene oxide/propyiene oxide with ethylene oxide
content nor more than 30 percent by weight
(a) Products transported under the provisions of this section should be acetylene free.
(b) For the purposes of this section the term "independent" means that a piping system or
venting system, for example, is in no way connected to another system and that there
are no means available for the potential connexion to other systems.
(c) (i) Unless cargo tacks are properly cleaned, these products should not be carried in
tanks which have contained as one of the three previous cargoes any product
known to catalyse polymerization , such as:
- ammonia, anhydrous and ammonia solutions;
- amines and amino solutions
- oxidizing substances (e.g. chlorine).
(ii) Before loading, tanks should be thoroughly anti 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 should be taken in the case of
ammonia in tanks made of steel other than stainless steel.
(iii) 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.
(iv) Tanks should be entered and inspected prior to each initial loading of these
products to ensure freedom from contamination, including 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.
(v) Tanks for the carriage of these products should be of steel or stainless steel
(vi) Tanks which have contained these products may be used for other cargoes after
thorough cleaning of tanks and associated pipework systems by washing or
(d) (i) All valves, flanges, fittings and accessory equipment should be of a type suitable
for use with these products and should be constructed of steel or stainless steel
or other material acceptable to the Administration. The chemical composition of
all material used should be submitted to the Administration for approval prior to
fabrication. Discs or disc faces, seats and other wearing parts of valves should be
made of stainless steel containing not less than 11 percent chromium.
(ii) Caskets should be constructed of materials which do not react with, dissolve in,
of 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 or similar fluorinated polymer may be accepted by the
(iii) 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.
(iv) 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.
Neoprene or natural rubber if it contacts the products.
Asbestos or binders used with asbestos.
Materials containing oxides of magnesium, such as mineral wools.
(e) Filling and discharge piping should extend to within 100 mm of the bottom of the tank
of any sump pit.
(f) (i) 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 from all other containment systems.
(ii) During discharging operations, the pressure in the cargo tank should be
maintained above 0.07 kp/cm2
(ii) The cargo may 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.
(g) Tanks carrying these products should be vented independently of tanks carrying other
products. facilities should be provided for sampling the tank contents without opening
the tank to atmosphere.
(h) Cargo hoses used for transfer of these products should be marked "FOR ALKYLENE
OXIDE TRANSFER ONLY".
(i) Hold spaces should be monitored for these products. Hold spaces surrounding
independent tanks type A and B should also be inerted and monitored for oxygen. The
oxygen content of these spaces should be maintained below 2 percent. Portable
sampling equipment is satisfactory.
(j) 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.
(k) Tanks should be designed for the maximum pressure expected to be encountered
during loading, carriage or unloading of cargo.
(l) Tanks for the carriage of propylene oxide with a design vapour pressure of less than
gauge and tanks for the carriage of ethylene oxide/propylene oxide mixtures
with a design vapour pressure of less than 1.2 kp/cm2
gauge should have a cooling
system to maintain the cargo below the reference temperature. For reference
temperature see 15.1.4(a).
(m) Pressure relief valve settings should not be less than 0.2 kp/. gauge and for type C
independent cargo tanks not greater than 7.0 kp/cm2
gauge for the carriage of propylene
oxide and not greater than 5.3 kp/cm2
gauge for the carriage of ethylene
oxide/propylene oxide mixtures.
(n) (i) The piping system for tanks to be loaded with these products should be
completely separate from piping systems for all other tanks, including empty
tanks, and from all cargo compressors. If the piping system thor the tanks to be
loaded with the product is not independent as defined in subparagraph (b) the
required piping separation must 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.
(ii) The product 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 kept on
board the ship. The Certificate of Fitness should be endorsed to include
reference to the approved cargo handling plans.
(iii) Before each initial loading of the product 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 connexion between a blank
flange and pipeline flange should be fitted with a wire and seal by the
responsible person to ensure that inadvertent removal of the blank flange is
(o) 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
lisle should be permanently kept on board by the master.
(p) 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 kp/cm2
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 percent v/v) 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.
(q) The cargo tank vapour space should be tested prior to and after loading to ensure that
the oxygen content is 2 percent (v/v) or less.
(r) 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/m2
/min. 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 perm it,
should be connected ready for immediate use during loading and unloading