Page 270 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

A positive test of the efficiency of the sealing arrangements can be
carried out by pressurising the holds with inert gas and applying a soapy
---ใช้เพื่อการศึกษาเท่านั้น---
solution to the sealing arrangements. Any leakage is readily detectable
and should be rectified by further adjustment of the closing devices in the
affected area.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
The cover joints should be examined for gas leakage when the
compartment is loaded with liquid cargo. Any gas or liquid leaks which
cannot be stopped by adjusting the closing devices should be marked or
noted, so that the jointing material can be examined when the opportunity
next arises and the joint made good. Additional sealing by means of tape
or compound may be necessary.

The gas tightness of the hatch covers will determine the frequency with
which the inert gas requires to be topped up.

Most combination carriers use synthetic rubber for the hatch seals, and
this material should be examined whenever a suitable opportunity occurs.
It is also advisable to carry a reasonable stock of jointing material of the
correct size, in order that repairs can be carried out at sea.

The hatch covers on combination carriers generally work, i.e. they move
slightly against the coaming, when the ship is in a seaway, and it is thus
possible for the steel hatch cover to rub on the steel coaming or remnants
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of a previous dry bulk cargo. Investigations have shown that this is
unlikely to provide a source of ignition. However, in order to avoid
unnecessary wear on the seals and in order to ease the opening and
closing of hatches, it is important to keep hatch cover runways clear of
foreign matter. After donning appropriate personal protective equipment, a
compressed air hose with a suitable nozzle may be used to clean the
trackways of foreign matter.

Owing to the height of hatch coamings, which are partially filled on
completion of loading a liquid cargo, all main deck openings into cargo
holds may have to withstand a positive pressure. Therefore, it is essential
that all seals and gaskets on tank cleaning covers, access hatches,
trimming hatches etc, provide an oil tight and gas tight seal. The seatings
should be cleaned to ensure a proper seal and all securing bolts should
be hardened down prior to loading a bulk liquid cargo.

14.1.9 Tank Washing

Any tank washing is to be carried out in accordance with the guidance
given in Section 11.3 when carrying oil, or when converting from oil to dry
bulk cargoes.

Cargo holds should not be used as slop tanks during cleaning because of
the risk of sloshing. Holds containing dirty ballast should not be
discharged when the ship is rolling or pitching. Hatch covers should not
be opened until the hold is gas free. All closing devices should be kept
secured to prevent movement of the hatch covers.

When cargoes other than oil are to be carried, it is essential that all holds
and cargo tanks, other than slop tanks, are emptied of oil and oil residues
and cleaned and ventilated to such a degree that the tanks are
completely gas free. They should then be inspected internally to confirm
this condition. The pumproom, cargo pumps, pipelines, duct keel and
other void spaces should be checked to ensure that they are free of oil
and hydrocarbon gas.

236 © ICS/OCIMF/IAPH 2006