Carbon disulphide may be carried either under a water pad
or under a suitable inert gas pad as specified in the following paragraphs.
15.3.1 Provision shall be
made to maintain a water pad in the cargo tank during loading, unloading
and transit. In addition, an inert-gas pad shall be maintained in
the ullage space during transit.
15.3.2 All openings shall
be in the top of the tank, above the deck.
15.3.3 Loading lines shall
terminate near the bottom of the tank.
15.3.4 A standard ullage
opening shall be provided for emergency sounding.
15.3.5 Cargo piping and vent
lines shall be independent of piping and vent lines used for other
cargo.
15.3.6 Pumps may be used
for discharging cargo, provided they are of the deepwell or hydraulically
driven submersible types. The means of driving a deepwell pump shall
not present a source of ignition for carbon disulphide and shall not
employ equipment that may exceed a temperature of 80°C.
15.3.7 If a cargo discharge
pump is used, it shall be inserted through a cylindrical well extending
from the tank top to a point near the tank bottom. A water pad shall
be formed in this well before attempting pump removal unless the tank
has been certified as gas-free.
15.3.8 Water or inert-gas
displacement may be used for discharging cargo, provided the cargo
system is designed for the expected pressure and temperature.
15.3.9 Safety relief valves
shall be of stainless steel construction.
15.3.10 Because of its low
ignition temperature and close clearances required to arrest its flame
propagation, only intrinsically safe systems and circuits are permitted
in the hazardous locations.
Carriage under suitable inert gas pad
15.3.11 Carbon disulphide
shall be carried in independent tanks with a design pressure of not
less than 0.06 MPa gauge.
15.3.12 All openings shall
be located on the top of the tank, above the deck.
15.3.13 Gaskets used in
the containment system shall be of a material which does not react
with, or dissolve in, carbon disulphide.
15.3.14 Threaded joints
shall not be permitted in the cargo containment system, including
the vapour lines.
15.3.15 Prior to loading,
the tank(s) shall be inerted with suitable inert gas until the oxygen
level is 2% by volume or lower. Means shall be provided to automatically
maintain a positive pressure in the tank using suitable inert gas
during loading, transport and discharge. The system shall be able
to maintain this positive pressure between 0.01 and 0.02 MPa, and
shall be remotely monitored and fitted with over/underpressure alarms.
15.3.16 Hold spaces surrounding
an independent tank carrying carbon disulphide shall be inerted by
a suitable inert gas until the oxygen level is 2% or less. Means shall
be provided to monitor and maintain this condition throughout the
voyage. Means shall also be provided to sample these spaces for carbon
disulphide vapour.
15.3.17 Carbon disulphide
shall be loaded, transported and discharged in such a manner that
venting to the atmosphere does not occur. If carbon disulphide vapour
is returned to shore during loading or to the ship during discharge,
the vapour return system shall be independent of all other containment
systems.
15.3.18 Carbon disulphide
shall be discharged only by submerged deepwell pumps or by a suitable
inert gas displacement. The submerged deepwell pumps shall be operated
in a way that prevents heat build-up in the pump. The pump shall also
be equipped with a temperature sensor in the pump housing with remote
readout and alarm in the cargo control room. The alarm shall be set
at 80°C. The pump shall also be fitted with an automatic shut-down
device to be activated if the tank pressure falls below atmospheric
pressure during the discharge.
15.3.19 Air shall not be
allowed to enter the cargo tank, cargo pump or lines while carbon
disulphide is contained in the system.
15.3.20 No other cargo handling,
tank cleaning or deballasting shall take place concurrent with loading
or discharge of carbon disulphide.
15.3.21 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 an 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 temperature permits, shall be connected ready for immediate
use during loading and unloading operations.
15.3.22 No cargo tanks shall
be more than 98% liquid-full at the reference temperature (R).
15.3.23 The maximum volume
(VL) of cargo to be loaded in a tank shall be:
where:
V |
= |
volume of the
tank |
ρR
|
= |
density of cargo at the reference temperature (R) |
ρL
|
= |
density of cargo at the loading temperature |
R |
= |
reference temperature |
15.3.24 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 approved by the Administration. A
copy of the list shall be permanently kept on board by the master.
15.3.25 Zones on open deck,
or semi-enclosed spaces on open deck within three metres of a tank
outlet, gas or vapour outlet, cargo pipe flange or cargo valve of
a tank certified to carry carbon disulphide, shall comply with the
electrical equipment requirements specified for carbon disulphide
in column i, chapter 17.
Also, within the specified zone, no other heat sources, like steam
piping with surface temperatures in excess of 80°C shall be allowed.
15.3.26 Means shall be provided
to ullage and sample the cargo without opening the tank or disturbing
the positive suitable inert gas blanket.
15.3.27 The product shall
be transported only in accordance with a cargo handling plan that
has been approved by the Administration. Cargo handling plans shall
show the entire cargo piping system. A copy of the approved cargo
handling plan shall be available on board. The International Certificate
of Fitness for the Carriage of Dangerous Chemicals in Bulk shall be
endorsed to include reference to the approved cargo handling plan.