Page 199 - International safety guide for oil tankers and terminals

SHIPBOARD OPERATIONS
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11.1.6.17
11.1.7
11.1.7.1
Before topping-off operations commence at an offshore berth, the
ship/shore communications system should be tested.
Where possible, the completion of loading should be done by
gravity. If pumps have to be used to the end, their delivery rate
during the ‘standby’ time should be regulated so that shore control
valves can be closed as soon as requested by the ship. Shore
control valves should be closed before the ship’s valves.
Checks After Loading
After the completion of loading, a Responsible Officer should
check that all valves in the cargo system are closed, that all
appropriate tank openings are closed and that pressure/vacuum
relief valves are correctly set.
Loading Static Accumulator Oils
General
Petroleum distillates often have electrical conductivities of less
than 50 picoSiemens/metre (pS/m) and thus fall into the category
of static accumulators.
ึ
Since the conductivities of distillates are not normally known, they
should all be treated as static accumulators unless they contain
an antistatic additive, which raises the conductivity of the product
above 50 pS/m. (See Section 11.1.7.9 regarding cautions on the
effectiveness of antistatic additives.) A static accumulator may
carry sufficient charge to constitute an incendive ignition hazard
during loading into the tank, and for up to 30 minutes after
completion of loading.
Bonding (see Section 3.2.2) is an essential precaution for
preventing electrostatic charge accumulation and its importance
cannot be over-emphasised. However, while bonding assists
relaxation, it does not prevent accumulation and the production of
hazardous voltages. Bonding therefore should not be seen as a
universal remedy for eliminating electrostatic hazards. This
Section describes methods for controlling electrostatic generation,
by preventing charge separation, which is another essential
precaution (see Section 3.1.2).
© ICS/OCIMF/IAPH 2006 165