8.4
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Specifications and Manuals - Inert Gas Systems - 8 Emergency Procedures - 8.4

8.4

 In the case of product carriers, if it is essential to clean tanks following a failure of the inert gas system and inerted conditions as defined in regulation 62.2.2 cannot be maintained, tank cleaning should be carried out with an external supply of inert gas connected to the system. Alternatively, if an external supply of inert gas is not connected to the ship, the following precautions should be taken, in addition to 8.3.1 to 8.3.5:

  • .1 Tank washing should be carried out only on one tank at a time.

  • .2 The tank should be isolated from other tanks and from any common venting system or the inert gas main and maximum ventilation output should be concentrated on that tank both before and during the washing process. Ventilation should provide as far as possible a free flow of air from one end of the tank to the other.

  • .3 The tank bottom should be flushed with water and stripped. The piping system including cargo pumps, cross-overs and discharge lines should also be flushed with water.

  • .4 Washing should not commence until tests have been made at various levels to establish that the vapour content in any part of the tank is below 10% of the lower flammable limit.

  • .5 Testing of the tank atmosphere should continue during the washing process. If the vapour level rises to within 50% of the lower flammable limit, washing should be discontinued until the vapour level has fallen to 20% of the lower flammable limit or less.

  • .6 If washing machines with individual capacities exceeding 60 m3/h are to be used, only one such machine shall be used at any one time on the ship. If portable machines are used, all hose connections should be made up and bonding cables tested for continuity before the machines are introduced into the tank and should not be broken until after the machines have been removed from the tank.

  • .7 The tank should be kept drained during washing. If build-up of wash water occurs, washing should be stopped until the water has been cleared.

  • .8 Only clean, cold seawater should be used. Recirculating systems should not be used.

  • .9 Chemical additives should not be used.

  • .10 All deck openings, except those necessary for washing and designed venting arrangements, should be kept closed during the washing process.

Parent topic: 8 Emergency Procedures
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.