Page 302 - International safety guide for oil tankers and terminals
P. 302
INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS
flanges do not rest on the jetty deck or other structure that may
render the insulating flange ineffective.
---ใช้เพื่อการศึกษาเท่านั้น---
When the connection is partly flexible and partly metal arm,
the insulating flange should be connected to the metal arm.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
For all metal arms, care should be taken to ensure that,
wherever it is convenient to fit the flange, it is not short
circuited by guy wires.
The location of the insulating flange should be clearly labelled.
insulating ึ
Thick One full Insulating One
plated length gasket
steel g washer
washer sleeve for for each
each bolt nut
nut
Figure 17.1 – Schematic diagram of insulating flange
17.5.5.2 Testing of Insulating Flanges
Insulating flanges should be inspected and tested at least
annually, or more frequently if considered necessary. Factors to
be taken into consideration when determining testing frequency
should include risk of deterioration due to environmental
exposure, usage, and damage from handling. It should be ensured
that the insulation is clean, unpainted and in an effective
condition. Readings should be taken between the metal pipe on
the shore side of the flange and the end of the hose or metal arm
when freely suspended. The measured value after installation
should be not less than 1,000 ohms. A lower resistance may
indicate damage to, or deterioration of, the insulation. The
terminal should maintain records of all tests on all the insulating
flanges within the terminal.
An insulating flange is designed to prevent arcing caused by low
voltage but high current circuits (usually below 1 volt, but
potentially up to around 5 volts and with currents rising to possibly
several hundreds of amps) that exist between ship and shore due
to stray currents, cathodic protection and galvanic cells. It is not
intended to give protection against the high voltage but low current
sparks associated with static discharge.
268 © ICS/OCIMF/IAPH 2006