Page 92 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

The following additional precautions should be taken against static electricity
during ullaging, dipping, gauging or sampling of static accumulator oils:
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Banning the use of all metallic equipment for dipping, ullaging and sampling
during loading and for 30 minutes after completion of loading. After the
30 minute waiting period, metallic equipment may be used for dipping,
้องสมุด ศูนย์ฝกพาณิชย์นาวี
ullaging and sampling, but it must be effectively bonded and securely
earthed to the structure of the ship before it is introduced into the tank, and
must remain earthed until after removal.
Banning the use of all non-metallic containers of more than 1 litre capacity
for dipping, ullaging and sampling during loading and for 30 minutes after
completion of loading.

Non-metallic containers of less than 1 litre capacity may be used for
sampling in tanks at any time, provided that they have no conducting
components and that they are not rubbed prior to sampling. Cleaning with a
high conductivity proprietary cleaner, a solvent such as 70:30% IPA:toluene
mix, or soapy water, is recommended to reduce charge generation. To
prevent charging, the container should not be rubbed dry after washing.

Operations carried out through a correctly designed and installed sounding
pipe are permissible at any time. It is not possible for any significant charge to
accumulate on the surface of the liquid within the sounding pipe and therefore
no waiting time is required. However, the precautions to be observed against
introducing charged objects into a tank still apply and if metallic equipment is
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used it should be bonded before being inserted into the sounding pipe.

Detailed guidance on precautions to be taken during ullaging, dipping and
sampling of static accumulator oils is given in Section 11.8.2.3. These
precautions should be rigidly adhered to in order to avoid hazards associated
with the accumulation of an electrical charge on the cargo.

3.2.2 Bonding
The most important countermeasure that must be taken to prevent an
electrostatic hazard is to bond all metallic objects together to eliminate the risk
of discharges between objects that might be charged and electrically insulated.
To avoid discharges from conductors to earth, it is normal practice to include
bonding to earth (‘earthing’ or ‘grounding’). On ships, bonding to earth is
effectively accomplished by connecting metallic objects to the metal structure
of the ship, which is naturally earthed through the sea.
งานห Ship/shore hose couplings and flanges, except for the insulating flange or
Some examples of objects which might be electrically insulated in hazardous
situations and which must therefore be bonded are:

single length of non-conducting hose required to provide electrical isolation
between the ship and shore. (See Section 17.5.)
Portable tank washing machines.

Manual ullaging and sampling equipment with conducting components.

The float of a permanently fitted ullaging device if its design does not

provide an earthing path through the metal tape.
The best method of ensuring bonding and earthing will usually be a metallic
connection between the conductors. Alternative means of bonding are
available and have proved effective in some applications, for example
semi-conductive (dissipative) pipes and ‘O’ rings, rather than embedded
metallic layers, for GRP pipes and their metal couplings.

58 © ICS/OCIMF/IAPH 2006