15.8.1 Products transported
under the provisions of this section shall be acetylene-free.
15.8.2 Unless cargo tanks
are properly cleaned, these products shall 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. benzenesulphonic);
-
.5 caustic alkalis (e.g. sodium hydroxide, potassium
hydroxide);
-
.6 ammonia and ammonia solutions;
-
.7 amines and amine solutions; and
-
.8 oxidizing substances.
15.8.3 Before loading, tanks
shall be thoroughly and effectively cleaned, to remove all traces
of previous cargoes from tanks and associated pipework, except where
the immediately 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.
15.8.4 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.
15.8.5 Tanks shall 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 shall be performed at intervals of not more than
two years.
15.8.6 Tanks for the carriage
of these products shall be of steel or stainless steel construction.
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 shall be of a type suitable for use
with the products and shall be constructed of steel or stainless steel
in accordance with recognized standards. Discs or disc faces, seats
and other wearing parts of valves shall be made of stainless steel
containing not less than 11% chromium.
15.8.9 Gaskets shall be constructed
of materials which do not react with, dissolve in, or lower the autoignition
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.
15.8.10 Insulation and packing,
if used, shall be of a material which does not react with, dissolve
in, or lower the autoignition 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
shall not be permitted in the cargo liquid and vapour lines.
15.8.13 Filling and discharge
piping shall extend to within 100 mm of the bottom of the tank or
any sump pit.
15.8.14.1 The containment
system for a tank containing these products shall have a valved vapour-return
connection.
15.8.14.2 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.
15.8.14.3 During discharge
operations, the pressure in the cargo tank must be maintained above
0.007 MPa gauge.
15.8.15 The cargo may 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.
15.8.16 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.
15.8.17 Cargo hoses used
for transfer of these products shall be marked "FOR ALKYLENE OXIDE
TRANSFER ONLY".
15.8.18 Cargo tanks, void
spaces and other enclosed spaces adjacent to an integral gravity cargo
tank carrying propylene oxide shall 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 shall be inerted. Such inerted spaces and tanks shall
be monitored for these products and oxygen. The oxygen content of
these spaces shall be maintained below 2%. Portable sampling equipment
is satisfactory.
15.8.19 In no case shall
air be allowed to enter the cargo pump or piping system while these
products are contained within the system.
15.8.20 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.
15.8.21 Propylene oxide
may be carried in pressure tanks or in independent or integral gravity
tanks. Ethylene oxide/propylene oxide mixtures shall be carried in
independent gravity tanks or pressure tanks. Tanks shall be designed
for the maximum pressure expected to be encountered during loading,
conveying and discharging cargo.
15.8.22.1 Tanks for the
carriage of propylene oxide with a design pressure less than 0.06
MPa gauge and tanks for the carriage of ethylene oxide/propylene oxide
mixtures with a design pressure of less than 0.12 MPa gauge shall
have a cooling system to maintain the cargo below the reference temperature.
15.8.22.2 The refrigeration
requirement for tanks with a design pressure less than 0.06 MPa 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 shall be included
in the conditions of carriage of the International Certificate of
Fitness for the Carriage of Dangerous Chemicals in Bulk.
15.8.23.1 Any cooling
system shall 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, shall be provided.
Each cooling plant shall be complete with the necessary auxiliaries
for proper operation. The control system shall also be capable of
being manually operated. An alarm shall be provided to indicate malfunctioning
of the temperature controls. The capacity of each cooling system shall
be sufficient to maintain the temperature of the liquid cargo below
the reference temperature of the system.
15.8.23.2 An alternative
arrangement may consist of three cooling plants, any two of which
shall be sufficient to maintain the liquid temperature below the reference
temperature.
15.8.23.3 Cooling media
which are separated from the products by a single wall only shall
be nonreactive with the products.
15.8.23.4 Cooling systems
requiring compression of the products shall not be used.
15.8.24 Pressure-relief-valve
settings shall not be less than 0.02 MPa gauge and for pressure 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 propylene
oxide/ethylene oxide mixtures.
15.8.25.1 The piping system for tanks to be loaded with
these products shall be separated (as defined in 3.1.4) 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
1.3.19), the required piping separation shall be accomplished by
the removal of spool-pieces, valves, or other pipe section 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.
15.8.25.2 These products
may be transported only in accordance with cargo-handling plans that
have been 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 blank flanges needed to meet the above piping separation requirements.
A copy of each approved cargo-handling plan shall be maintained on
board the ship. The International Certificate of Fitness for the Carriage
of Dangerous Chemicals in Bulk shall be endorsed to include reference
to the approved cargo-handling plans.
15.8.25.3 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 a pipeline flange
shall be fitted with a wire and seal by the responsible person to
ensure that in-advertent removal of the blank flange is impossible.
15.8.26.1 No cargo tanks
shall be more than 98% liquid-full at the reference temperature.
15.8.26.2 The maximum
volume to which a cargo tank shall be loaded is:
Where
|
VL
|
= |
maximum
volume to which the tank may be loaded |
|
V |
= |
volume of the
tank |
|
ρR
|
= |
density
of cargo at the reference temperature |
|
ρL
|
= |
density
of cargo at the loading temperature and pressure |
15.8.26.3 The maximum
allowable tank filling limits for each cargo tank shall 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 shall be permanently kept on board by the master.
15.8.27 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 maloperation of refrigeration
systems. 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.
15.8.28 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.
15.8.29 A 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
10 l /m2/min. Remote manual operation
shall 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 event of fire in the areas protected. The water-spray
system shall be capable of both local and remote manual operation,
and the arrangement shall ensure that any spilled cargo is washed
away. Additionally, a water hose with pressure to the nozzle, when
atmospheric temperatures permit, shall be connected ready for immediate
use during loading and unloading operations.
15.8.30 A remotely operated,
controlled closing-rate, shutoff valve shall be provided at each cargo-hose
connection used during cargo transfer.