SOLAS-2012

Chapter II-2, Part B
SOLAS 74/78
page 21/112
5.5.3 General requirements for inert gas systems
5.5.3.1 The inert gas system shall be capable of inerting, purging and gas-freeing empty tanks and
maintaining the atmosphere in cargo tanks with the required oxygen content.
5.5.3.2 The inert gas system referred to in paragraph 5.5.3.1 shall be designed, constructed and tested in
accordance with the Fire Safety Systems Code.
5.5.3.3 Tankers fitted with a fixed inert gas system shall be provided with a closed ullage system.
5.5.4 Requirements for equivalent systems
5.5.4.1 Where an installation equivalent to a fixed inert gas system is installed, it shall:
.1 be capable of preventing dangerous accumulations of explosive mixtures in intact cargo
tanks during normal service throughout the ballast voyage and necessary in-tank operations; and
.2 be so designed as to minimize the risk of ignition from the generation of static electricity by
the system itself.
5.6 Inerting, purging and gas-freeing
5.6.1 Arrangements for purging and/or gas-freeing shall be such as to minimize the hazards due to
dispersal of flammable vapours in the atmosphere and to flammable mixtures in a cargo tank.
5.6.2 The procedure for cargo tank purging and/or gas-freeing shall be carried out in accordance with
regulation 16.3.2.
5.6.3 The arrangements for inerting, purging or gas-freeing of empty tanks as required in paragraph
5.5.3.1 shall be to the satisfaction of the Administration and shall be such that the accumulation of
hydrocarbon vapours in pockets formed by the internal structural members in a tank is minimized and that:
.1 on individual cargo tanks, the gas outlet pipe, if fitted, shall be positioned as far as practicable
from the inert gas/air inlet and in accordance with paragraph 5.3 and regulation 11.6. The inlet of
such outlet pipes may be located either at deck level or at not more than 1 m above the bottom of
the tank;
.2 the cross-sectional area of such gas outlet pipe referred to in paragraph 5.6.3.1 shall be
such that an exit velocity of at least 20 m/s can be maintained when any three tanks are being
simultaneously supplied with inert gas. Their outlets shall extend not less than 2 m above deck
level; and
.3 each gas outlet referred to in paragraph 5.6.3.2 shall be fitted with suitable blanking
arrangements.
5.7 Gas measurement and detection
5.7.1 Portable instrument
Tankers shall be equipped with at least one portable instrument for measuring oxygen and one for
measuring flammable vapour concentrations, together with a sufficient set of spares. Suitable means shall
be provided for the calibration of such instruments.
5.7.2 Arrangements for gas measurement in double–hull spaces and double bottom–spaces