Appendix 1 - Necessary Additional Pressure (NAP) Test
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Resolutions - Assembly - IMO Resolution A.761(18) – Recommendation on Conditions for the Approval of Servicing Stations for Inflatable Liferafts – (Adopted on 4 November 1993)Amended by Resolution MSC.55(66)Amended by Resolution MSC.388(94) - Annex - Recommendation on Conditions for the Approval of Servicing Stations for Inflatable Liferafts - Appendix 1 - Necessary Additional Pressure (NAP) Test

Appendix 1 - Necessary Additional Pressure (NAP) Test

  1 Plug the pressure relief valves.

  2 Gradually raise the pressure to the lesser of 2.0 times the working pressure or that sufficient to impose a tensile load on the inflatable tube fabric of at least 20% of the minimum required tensile strength.

  3 After 5 minutes, there should be no seam slippage, cracking, or other defects (Resolution A.521(13), part 1, paragraph 5.18.4.1), or significant pressure drop. If cracking in the buoyancy tubes is audible, the liferaft should be condemned; if no cracking is heard, the pressure in all buoyancy chambers should be reduced simultaneously by removing the plugs from the pressure relief valves.

  4 Liferaft manufacturers should include tables in their servicing manuals of exact NAP test pressures corresponding to their particular tube sizes and fabric tensile strength requirements, calculated according to the equation:

Parent topic: Annex - Recommendation on Conditions for the Approval of Servicing Stations for Inflatable Liferafts
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.