Gas Free Survey Procedure

Guidelines for Preparing Vessel for Gas-Free Inspection
To enable the vessel to enter port or shipyard for repair without delay, the Master, when
preparing the vessel for certifying free from flammable vapour (gas-free inspection), is
required to ensure that the following important requirements are complied with:

(a) Prior to the inspection of a vessel, which has carried Class A or Class B petroleum in
bulk, the master is required to certify that all empty cofferdams and all the compartments,
pumps and pipelines which contained petroleum have since the last discharge of such
petroleum.

(b) All compartments (including cargo tanks, pump-rooms, cofferdams, and void spaces) to
be opened and freed from liquid petroleum and petroleum vapour. As far as possible they
must also be freed from water, sediment, scale and rust or anything which might retain
petroleum or its vapour.

(c) All valves on cargo lines (including vapour lines if available), both in the tanks and on
deck should be opened and blank flanges removed.

(d) Consistent with docking requirements, permanent segregated ballast tanks are allowed
to be in ballast before issuing the gas free certificate.

(e) All slops on board have been discharged and that the slop tanks and any available
residue tank onboard are thoroughly cleaned, ventilated and free from flammable vapour.
The following points are often overlooked by the Master of the vessel and the cause of gasfree
certification not being issued:
(a) Gas-Freeing of cofferdams (the fact that a cofferdam is normally kept full of water does
not mean that it is gas-free).
(b) Available vapour line openings on deck were not opened at the time of inspection.
(c) Washing of pipelines, including crossovers and other possible ‘dead ends’ and complete
draining thereof.
(d) Removal of sediment, sludge and scale (especially on stringers and similar places).
(e) Cleaning of heating-coils.
(f) Cleaning of manifold lines (including the drip trays).
(g) Emptying of pump-room bilges.
The Inspector /Surveyor will inspect the following parts of the vessel with a combustible
gas indicator to determine the presence of flammable vapour:
(i) Pipeline including vapour line openings on deck;
(ii) All empty cargo tanks;
(iii) Cofferdams or void spaces;
(iv) Pump-rooms;
(v) Ballast tanks (if not fully filled with water);
(vi) Slop tanks, residue tank; and
(vii) Bunker tanks (if the vessel is to enter a shipyard).

A Gas-Free Certificate will be issued to the Master of the vessel only if the Inspector of
Petroleum is completely satisfied that items (i) to (vi) mentioned in para 4 above are free
from flammable vapour. This certificate will only permit the vessel to proceed to other
anchorages within the port. If a Gas-Free Certificate for entering a shipyard is required, in
addition to being satisfied that items (i) to (vi) are free from flammable vapour.
The Gas-Free Certificate is valid for a period of 7 days from the date of issue.

Should the Certificate expire or any change in the condition occurred, it is necessary for the
Inspector /Surveyor to re-inspect the vessel and a new Certificate issued thereupon. It is
the responsibility of the Master of the vessel to monitor the expiry date and the condition
and should the Certificate expire or any change occur. It is the responsibility of the Master
of the vessel to inform the Inspector ?Surveyor through the vessel's agent in order that a
further inspection be carried out.

Footnote
1. Class “A” petroleum means any petroleum the flash-point of which is less than 23
degrees Celsius and includes liquefied petroleum gas.
2. Class “B” petroleum means any petroleum the flash-point of which is 23 degrees Celsius
or more but less than 60 degrees Celsius.