Page 302 - International safety guide for oil tankers and terminals
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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
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