9.1.1 A piping system should
be provided to enable each cargo tank to be safely gas-freed, and
to be safely purged with cargo gas from a gas-free condition. The
system should be arranged to minimize the possibility of pockets of
gas or air remaining after gas-freeing or purging.
9.1.2 A sufficient number of
gas sampling points should be provided for each cargo tank in order
to adequately monitor the progress of purging and gas-freeing. Gas
sampling connections should be valved and capped above the main deck.
9.1.3 For flammable gases,
the system should be arranged to minimize the possibility of a flammable
mixture existing in the cargo tank during any part of the gas-freeing
operation by utilizing an inerting medium as an intermediate step.
In addition, the system should enable the cargo tank to be purged
with an inerting medium prior to filling with cargo vapour or liquid,
without permitting a flammable mixture to exist at any time within
the cargo tank.
9.1.4 Piping systems which
may contain cargo should be capable of being gas-freed and purged
as provided in 9.1.1 and 9.1.3.
9.1.5 Inert gas utilized in
these procedures may be provided from the shore or from the ship.