Approval criteria for fire extinguishing systems: UK21/F018
Adopted EU recommendation FIRE-059. UK approved recommendation on the approval criteria for fire extinguishing systems for machinery spaces.
Question
There is a possible inconsistency in the provisions of the ‘Revised Guidelines for the approval of fixed aerosol fire-extinguishing systems equivalent to fixed gas fire extinguishing systems (MSC.1/Circ.1270)’, regarding the extinguishing criteria for wood cribs, as it is not clear from the classification criteria if total extinguishment of the cribs by the aerosol system is one of the acceptance criteria.
The following clauses are taken from MSC.1/Circ.1270:
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3.5.4.1.3 Pre-burn time: wood crib - 3 separate tests, one of 2 minutes, one of 4 minutes and one of 6 minutes.
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3.5.4.2 Discharge time: Aerosol agents should be discharged at a rate sufficient to achieve 100% of the minimum design density in 120 s or less.
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3.5.4.3 Hold time: After the end of agent discharge the test enclosure should be kept closed for 15 minutes.
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4.4 Classification criteria: The wood crib weight loss should be no more than 30% during the 2 minute pre-burn test, 50% during the 4 minute pre-burn test and 60% during the 6 minute pre-burn test.
It is not clear, when conducting the wood crib fire test, if:
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the fires should be totally extinguished by the aerosol system within the discharge time + the hold time, i.e. 2 + 15 minutes, before carrying out the weight loss procedure; or
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the fires are not extinguished at the end of the discharge time, then they may be manually extinguished to carry out the weight loss procedure, i.e. no hold time is applied.
According to MSC.1/Circ.1270, clause 4.1, “Class B fires should be extinguished within 30 s of the end of discharge. At the end of the hold period there should be no re-ignition upon opening the enclosure”.
It is known that aerosols have a particular difficulty fully extinguishing deep seated Class A fires, thus the wood crib acceptance criteria were linked to weight loss only.
What are the extinguishing criteria for wood cribs?
Recommendation
Based on acceptance criteria for other extinguishing systems (water-mist fire extinguishing systems as per item UK/3.39 (IMO MSC/Circ.1165) and high-expansion foam systems as per item UK/3.61 a) + b) (IMO MSC.1/Circ.1384), which specify under sections 5 that there shall be no re-ignition), the acceptance criteria of Aerosol systems should not be less stringent than for other equivalent systems for marine application. Hence, the acceptance criteria for Aerosol systems according to item UK/3.46 and IMO MSC.1/Circ.1270 should be total extinguishment of the cribs and no re-ignition. Manual extinguishment is not acceptable.
Additionally, an Aerosol system cannot under any circumstances be type approved according to the Merchant Shipping (Marine Equipment) Regulations 2016 as amended based on IMO MSC.1/Circ.1270 until the substance has been officially classified as harmless to humans and the environment by a recognized health authority.
References
- MSC.1/Circ. 1270 including Corrigendum 1
- MSN 1874 as amended
- The Merchant Shipping (Marine Equipment) Regulations 2016 as amended
Items affected
- UK/3.46
More information
Maritime and Coastguard Agency
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Southampton
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Telephone: +44 (0) 203 817 2000
Email: MEQA@mcga.gov.uk
Website: www.gov.uk/mca