CLOSED OPERATION

Vessels carrying volatile, flammable, toxic or noxious cargoes must be provided with fixed closed ullage gauges in all cargo tanks with local or remote indication.
In addition, in oil and chemical carriers, vapour locks must be fitted on each cargo tank to consent sampling, dipping, water and temperature detection without need of opening the cargo tanks. The use of portable hermetic tapes as primary gauging system will not be accepted. The following fixed closed ullaging devices are deemed acceptable: mechanically operated floating gauges, electrical capacitance gauges or electronic probes, ultrasonic and sonic methods.
In case of break down of a fixed gauge, ullage operations should temporarily be performed by means of portable hermetic tapes through the vapour locks, provided that correction factors are available and certified so that ship’s original calibration table may be used.
Correction factors should take into account the difference in height with respect to the original datum and differences due to the trim and list of the ship. The number of portable hermetic tapes available on board must be in accordance with the provisions of IMO MSC/Circ. 551, taking into account the foregoing.
Slip tubes in gas tankers are not deemed to satisfy the requirements for fixed-closed ullage gauges.

 

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