2.5.1 Each cargo tank of a tanker should be equipped
with an overflow control system.
2.5.2 The overflow control system required by
paragraph 2.5.1 should:
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.1 be independent of the cargo gauging system;
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.2 come into operation when the normal tank loading
procedures fail to stop the tank liquid level exceeding the normal
full condition;
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.3 give a visual and audible tank overflow alarm
to the ship's operator;
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.4 provide an agreed signal for sequential shutdown
of onshore pumps or valves or both and of the ship's valves. The signal
as well as the pump and valve shutdown may be dependent on operator's
intervention. The use of shipboard automatic closing valves should
be permitted only when specific approval has been obtained from the
Administration and the Port Administration concerned;
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.5 have alarms fitted in the cargo control room,
where provided, but in each case in such a position that they are
immediately received by responsible members of the crew;
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.6 alarm in the event of loss of power to the
alarm system or failure of the electrical circuitry to the tank level
sensor; and
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.7 be able to be checked at the tank for proper
operation prior to each transfer or contain an electronic self-testing
feature which monitors the condition of the alarm circuitry and sensor.