Page 207 - International safety guide for oil tankers and terminals

SHIPBOARD OPERATIONS
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11.1.9
11.1.9.1
11.1.9.2
Avoiding loading when the wind speed is less than 5 knots.
Using very low initial flow rates into tanks.
Using very low topping-off rates.
Avoiding a partial vacuum in the loading line.
Avoiding loading oil that is hot due to lying in shore lines exposed to
the sun. If this is unavoidable, this oil should be loaded to tanks that
vent well clear of the superstructure (e.g. forward tanks).
Providing additional supervision to see that gas dispersion is
monitored and to ensure compliance with all safety requirements.
Monitoring inert gas main pressure where this gives an indication of
the cargo tank pressure. A maximum pressure in the order of
1,000 mm WG should be used and the loading rate adjusted
accordingly.
To prevent gassing-up of cargo pumps, the expected True Vapour
Pressure (TVP) of the cargo at the discharge port should, under normal
circumstances, not exceed 0.7 bar for both crude oil and products. A TVP
of up to 0.8 bar may be considered if the ship is fitted with an inert gas
system, or if some other acceptable method of pressurisation is to be
used during discharge.
ึ 2
Loading Cargoes Containing Hydrogen Sulphide (H S)
General
The number of cargoes containing significant quantities of
Hydrogen Sulphide (H 2 S) is increasing. In addition, levels of H 2 S
contained within the cargoes are also increasing. Guidance on
H 2 S toxicity is to be found in Section 2.3.6 and guidelines on gas
measurement and gas testing are to be found in Sections 2.4
and 8.2.
This Section provides practical guidance on operational measures
that can be taken to minimise the risks associated with loading
cargoes containing H 2 S, commonly referred to as ‘sour’ cargoes.
Precautions when Loading Cargoes
Containing H S
2
The following precautions should be considered when preparing to
load sour cargoes:
Before arriving at the loading port, ensure that the cargo
system is free of leaks from the cargo piping, tank fittings and
the venting system. Test the heating coils to prevent possible
transference of H 2 S into the low pressure steam system.
Any liquid filled pressure vacuum breakers should be checked
to ensure that they are correctly filled.
Check that all doors and ports can be securely closed to
prevent any small gas ingress.
When loading a cargo containing H 2 S:
A safety plan should be produced for the loading operation
which should include guidance on the venting procedure,
© ICS/OCIMF/IAPH 2006 173