5.5.1 Ullaging devices of the closed type should
be used to avoid the opening of ullage ports.
5.5.2 However, it may be necessary to infrequently
relieve the inert gas pressure in the cargo tanks on certain occasions
to permit manual tank gauge or cargo sampling before or after cargo
is transferred. If this is done, no cargo or ballasting operation
is to be undertaken and a minimum number of small tank openings are
to be uncovered for as short a time as necessary to enable these measurements
to be completed. Manual gauging or cargo sampling may be performed
during the following four periods:
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.1 At the loading port, prior to cargo loading.
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.2 At the loading port, after cargo loading.
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.3 At the discharge port, prior to cargo discharge.
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.4 At the discharge port, after cargo discharge.
5.5.3 The tanks should then be re-pressurized
immediately after the measurements or cargo samples have been taken.
5.5.4 If the tank is opened prior to cargo transfer,
cargo transfer should not be commenced until all the conditions have
been checked and are in order. Similarly, if the tank is opened after
cargo transfer, normal ship operations should not be commenced until
all the conditions have been checked and are in order.
5.5.5 During cargo transfer the oxygen content
and pressure of the inert gas in the inert gas main should be continuously
recorded (see regulation 62.16.1.1 and .2).