Page 221 - International safety guide for oil tankers and terminals

SHIPBOARD OPERATIONS

Where they are fitted, interlock devices to prevent too many cargo and
ballast tanks from being operated simultaneously, thereby causing an
Tank Cleaningศึกษาเท่านั้น---
excessive free surface effect, should always be maintained in full
operational order, and should never be overridden.

งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
Ships that operate with limited metacentric height should be equipped
with a loading computer that calculates metacentric height.

11.2.3 Heavy Weather Ballast

It is imperative that Masters and officers be aware that partially loading a
cargo tank with heavy weather ballast may present a potential problem
due to ‘sloshing’. The combination of free surface and the flat tank bottom
can result in the generation of wave energy of sufficient power to severely
damage internal structure and pipelines.

11.2.4 Loading and Discharge Planning
Ballasting and deballasting must be planned and programmed around the
cargo operations so as to avoid exceeding specified draught, trim or list
requirements, while at the same time keeping shear force, bending
moments and metacentric height within prescribed limits.
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11.3

11.3.1 General
This Section deals with procedures and safety precautions for cleaning
cargo tanks after the discharge of volatile or non-volatile petroleum
carried in non-gas free, non-inert or inert tanks. Guidance is also given on
the cleaning of contaminated ballast spaces.

11.3.2 Tank Washing Risk Management

All tank washing operations should be carefully planned and documented.
Potential hazards relating to planned tank washing operations should be
systematically identified, risk assessed and appropriate preventive
measures put in place to reduce the risk to as low as reasonably
practicable (ALARP).
In planning tank washing operations, the prime risk is fire or explosion
arising from simultaneous presence of a flammable atmosphere and a
source of ignition. The focus therefore should be to eliminate one or more
of the hazards that contribute to that risk, namely the sides of the fire
triangle of air/oxygen, ignition source and fuel (i.e. flammable vapours).
Inert Tanks
The method that provides the lowest risk is washing the tank in an inert
atmosphere. The inert condition provides for no ambiguity; by definition,
to be deemed inert, the tank MUST meet the SOLAS requirement for
inerting of the cargo tanks and reducing the oxygen content of the
atmosphere in each tank to a level at which combustion cannot be
supported.

Failure to prove through direct measurement that the tank is inert means,
by default, that the tank MUST be considered to be in the non-inert
condition.

© ICS/OCIMF/IAPH 2006 187