Page 237 - International safety guide for oil tankers and terminals
P. 237
SHIPBOARD OPERATIONS
Ballast must be loaded and discharged in such a way as to avoid the
ship’s hull being subjected to excessive stress at any time during the
---ใช้เพื่อการศึกษาเท่านั้น---
operation.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
11.6.3 Loading Cargo Tank Ballast
When loading ballast into cargo tanks, the following precautions should
be observed:
Before taking ballast into tanks containing hydrocarbon vapour, the
Responsible Officer should consult with the Terminal Representative
and all safety checks and precautions applicable to the loading of
volatile petroleum must be observed. Closed loading procedures
should be followed.
On crude oil tankers, any tank to be ballasted should be crude oil
washed beforehand.
When taking ballast into cargo tanks that contain hydrocarbon vapour,
gas is expelled which may be within the flammable range on mixing
with air. This gas should therefore be vented through the recognised
venting system.
When taking ballast into tanks that previously contained cargoes that
required closed operations, the ballast should also be loaded ‘closed’
by following the procedures in Section 11.1.6.6.
ึ
Ballast should not be loaded over the top (overall) into tanks containing
hydrocarbon vapour.
The guidance given in Section 11.1.3 should be followed when
operating ballast tank valves.
11.6.3.1 Operation of Cargo Pumps
When starting to ballast, cargo pumps should be operated so that
no oil is allowed to escape over board when the sea suction valve
is opened. Reference should be made to the ICS/OCIMF
publication ‘Prevention of Oil Spillages Through Cargo Pumproom
Sea Valves’.
11.6.3.2 Sequence of Valve Operations
The following procedures should be adopted when loading ballast
into a non-inerted tank that contains hydrocarbon vapour:
The tank valve should be the first valve opened and the sea
valve should be the last.
The initial flow of ballast should be restricted at the pump
discharge, so that the entrance velocity into the tank is less
than 1 metre/second until the longitudinals are covered or, if
there are no longitudinals, until the depth of the ballast in the
tank is at least 1.5 metres.
These precautions are required to avoid the spraying effect that
may lead to a build-up of an electrostatic charge in a mist or spray
cloud near the point where the ballast enters the tank (see
Chapter 3). When a sufficient charge exists, there is always the
possibility of a static discharge and ignition.
© ICS/OCIMF/IAPH 2006 203
