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    Extinguishers: Carbon Dioxide Hose Replacement

    By Mark Conroy


    The United States Coast Guard (USCG) issued a Marine Safety Alert bulletin on December 19, 2017, regarding fixed carbon dioxide (CO2) systems. The bulletin evolved from a safety inspection of a CO2 system onboard a container ship. The focus was on the flexible connectors (hoses) between the high-pressure cylinders and the piping manifold. The investigation determined that due to problems with the hoses, the CO2 system might either fail to operate correctly or might not operate at all. The subheading to the bulletin reads, “When your hoses aren’t right, you might lose the firefight”.

    The inspectors found the connector hoses were wrapped around the cylinder valves, causing a severe bend in the hose, which exerted an excessive stress on the hose at the bend. They also discovered significant cracking of the hoses. The severe bends in the hoses were caused by either the cylinders rotating in-place (they were not secured correctly) or that they were installed that way. The bulletin describes methods for assuring cylinders do not rotate in place.

    The bulletin also identifies ozone cracking of the hoses as a contributing factor in the deterioration of the hoses. That condition is well established and has to do with the minute amounts of ozone in the air reacting with polymers in the hose, causing degradation. Although exacerbated by the severe bends in the hoses, ozone cracking is a very common phenomenon with rubber hoses and is sometimes simply called “dry rot” due to its appearance. The only remedy for severe ozone cracking is replacement of the hose.

    Other uses for hose include hand-portable CO2 extinguishers, wheeled CO2 extinguishers, and fixed CO2 hose line systems. Those hoses comply with UL 154, Standard for Carbon Dioxide Extinguishers with 10,000 psi burst and 2500 psi working pressures, rubber-covered, wire-braided, and brass couplings.

    Listed Replacement Carbon Dioxide Hoses

    Application Length Fittings (female) P/N
    10-20 lb CO2 Extinguisher 32 inches 1/4" x 1/4" 32A
    10-20 lb CO2 Extinguisher 32 inches 1/4" x 3/8" 32B
    10-20 lb CO2 Extinguisher 36 inches 1/4" x 1/4" 36A
    10-20 lb CO2 Extinguisher 36 inches 1/4" x 3/8" 36B
    50 lb or Larger Wheeled or Fixed 15 ft 1/2" x 1/2"* 15FF
    50 lb or Larger Wheeled or Fixed 40 ft 1/2" x 1/2"* 32A
    *Use adapter P/N CPLM to change 1/2" female hose end to 1/2" male.

    The bulletin references International Maritime Organization (IMO) MSC.1/Circ.1318, Guidelines for the Maintenance and Inspections of Fixed Carbon Dioxide Fire-Extinguishing Systems. That document recommends that hoses be replaced at intervals, as recommended by manufacturers “but not exceeding every 10 years”.

    Replacing CO2 hoses at intervals of every 10 years (or sooner when severe ozone cracking occurs) will ensure that reliable hoses are in-place for portable extinguishers, wheeled units, fixed hose lines, and CO2 systems. That is so that problems will not occur with your customer’s hoses when they are needed most—during a fire emergency. As the USCG says, “When your hoses aren’t right, you might lose the firefight”.


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    Mark Conroy is an engineer in our Boston, MA office and a principal member of the NFPA Technical Committee on Portable Fire Extinguishers. © 2018 Brooks Equipment.

    Disclaimer: The opinions expressed in the above Tech Series article are the author’s only and provide limited information. Although the information is believed to be reliable, Brooks Equipment Company, LLC expressly disclaims any warranty with respect to the information and any liability for errors or omissions. The user of this article or the product(s) is responsible for verifying the information’s accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.