Page 246 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

of the tank. Dipping, ullaging and sampling within a metal
sounding pipe are therefore permissible at any time, provided that
---ใช้เพื่อการศึกษาเท่านั้น---
any metallic equipment is properly earthed. Non-metallic
equipment may also be used in sounding pipes, although the
precautions against introducing charged objects must be applied.
When tank washing operations are performed, it is essential thatย์นาวี
11.8.2.4 Static Non-Accumulator Oils

The possibility exists of a flammable atmosphere being present
above a static non-accumulator oil in a non-inerted or non-gas
free environment and therefore the precautions summarised in
Section 11.8.2 and Figure 11.5 should be followed.

งานห้องสมุด ศูนย์ฝกพาณิช
11.8.2.5 Ullaging and Dipping in the Presence of
Water Mists

there should be no unearthed metallic conductor in the tank, and
that none should be introduced while the charged mist persists,
i.e. during washing and for 5 hours after the completion of the
operation. Earthed and bonded metallic equipment can be used at
any time because any discharges to the water mist take the form
of a non-incendive corona. The equipment can contain or consist
entirely of non-metallic components. Both intermediate conductors
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and non-conductors are acceptable, although the use of
polypropylene ropes, for example, should be avoided. (See
Section 3.3.4.)

It is absolutely essential, however, that all metallic components are
securely earthed. If there is any doubt about earthing, the
operation should not be permitted.

Ullaging and dipping operations carried out via a full-depth
sounding pipe are safe at any time in the presence of a wash
water mist.

11.8.3 Measuring and Sampling Inerted Tanks
Ships fitted with inert gas systems will have closed gauging systems for
taking measurements during cargo operations. In addition, many ships will
be provided with vapour locks to enable closed gauging and sampling to
be undertaken for custody transfer purposes.

Ships equipped with a vapour lock on each cargo tank can measure and
sample cargo without reducing the inert gas pressure. In many cases, the
vapour locks are used in conjunction with specially adapted measurement
devices, including sonic tapes, samplers and temperature tapes. When
using the equipment, the valves of the vapour lock should not be opened
until the instrument is properly attached to the standpipe. Care should be
taken to ensure that there is no blow-back of vapour.

Sonic tapes, temperature tapes etc must be used in accordance with
good safety practices and the manufacturer’s instructions. The
requirements for portable electrical equipment apply to these
measurement devices (see Section 4.3).

On ships that are not equipped with vapour locks, special precautions
need to be taken for the open measurement and sampling of cargo

212 © ICS/OCIMF/IAPH 2006