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    Recharging Dry Chemical Extinguishers

    By Mark Conroy

    Although stored pressure dry chemical extinguishers are manufactured as either rechargeable or non-rechargeable, only rechargeable extinguishers are permitted to be recharged. Knowing the minimum requirements and procedures for recharging these extinguishers is paramount for fire equipment distributors that make a living by installing and servicing extinguishers. Here are some questions, with answers, to some very basic but important questions regarding recharging of these extinguishers.

    What is recharging?
    To perform recharging, an extinguisher is depressurized, examined to determine if parts need replacement, filled with extinguishing agent, and pressurized with nitrogen. A record tag, service collar, and tamper seal is required for each recharged extinguisher.

    When are stored pressure dry chemical extinguishers recharged?
    All rechargeable dry chemical extinguishers are recharged for the following reasons:

    • When the extinguisher has had any use, including partial discharge
    • When the pressure gauge is below (or above) the operable range
    • When extinguisher weight is below (or above) the allowable gross weight range on the nameplate
    • When extinguisher is opened for maintenance
    • When extinguisher is opened for hydrostatic testing
    • When indicated by an inspection

    Where are the requirements and procedures for recharging stored pressure dry chemical extinguishers?
    The minimum requirements for recharging extinguishers are contained in NFPA 10 and the procedures for recharging are in the product service manuals.

    Can you convert one type of dry chemical extinguisher to another?
    Extinguishers can not be converted from one type to another. ABC dry chemical is acidic and BC dry chemicals are alkaline. They are chemically incompatible and dangerous pressures could build up, causing the cylinder to fail. Additionally, the fire fighting capacity of each of the BC dry chemicals is different. So filling a Purple K extinguisher with ordinary dry chemical would make the unit less effective and the fire extinguishing capability of the extinguisher would not match the rating on the nameplate. These are just a couple of reasons that NFPA 10 prohibits the practice of converting extinguishers from one type to another.

    How do you know you’ve added the right amount of dry chemical?
    The amount of recharge agent is verified by weighing the extinguisher. A properly recharged extinguisher has the same weight (gross weight) as the gross weight shown on the extinguisher nameplate. Typically, the nameplate provides a weight range (plus or minus a few ounces).

    What type of nitrogen is permitted for recharging?
    The expellant gas used for pressurizing stored pressure dry chemical extinguishers is industrial-grade nitrogen with a maximum dew point of -60°F.

    Is it permissible to pressurize an extinguisher directly from a nitrogen cylinder?
    Connecting an extinguisher directly to a nitrogen cylinder could allow the extinguisher to be over-pressurized and rupture. This practice is therefore prohibited. The nitrogen cylinder must have a pressure regulator (P/N 2550) to help assure extinguishers aren’t over-pressurized.

    How do you leak check an extinguisher?
    Once an extinguisher has been filled with agent and pressurized, a leak test must be performed to make sure that the extinguisher is not a leaker. This is a requirement of NFPA 10. Leak detector fluid (P/N LD1) is applied to top of the valve threads and the gauge threads. If bubbles form, you’ve got a leaker and the valve or gauge needs to be tightened or the extinguisher needs to be broken down and the problem corrected.

    Are service tags required for recharging?
    Every extinguisher that has been recharged is required to have a tag attached providing the name of the servicing company, month and year, and initials of technician performing the work. Some states also require license numbers on tags. Still other states require special tag designs, which are available from Brooks. It’s always best to check with your local authority having jurisdiction to make sure you have the right tags. Some states have very specific criteria for service tags and may require you to submit samples to the State Fire Marshal for approval. Note that penalties for non-compliance can be severe.

    Are service collars required for recharging?
    Since the valve assembly needs to be removed, in order to recharge stored pressure dry chemical extinguishers, a verification-of-service collar is required to be installed around the neck of the extinguisher. Also a new tamper seal must be installed. Certain states require special collars and/or tamper seals. It is always best to check with your local authority having jurisdiction to make sure you have the right service collars and tamper seals and are in compliance with state laws and regulations.

    How does recharging affect the annual maintenance and 6-year teardown intervals?
    Whenever an extinguisher is recharged, both an internal and external examination is required to be conducted on the extinguisher. When the internal and external examination is performed, the annual maintenance and 6-year teardown intervals begin from that date.

    We carry a full line of recharge chemical, service tags, tamper seals, and verification-of-service collars that you will need for servicing all brands of dry chemical extinguishers. We also have the equipment and tools you will need to perform recharging correctly and efficiently. The table below provides the part numbers for some of the most common equipment needed by fire equipment service companies for recharging dry chemical extinguishers.

    Recharge Equipment

    Description P/N Notes
    Scoop NAS1 Aluminum scoop for filling dry chemical extinguishers.  
    Small Funnel FF1 Galvanized steel with proper screens to prevent jamming.  
    Large Funnel FF2 Similar to small funnel but for filling larger extinguishers.  
    Blow-Out Bag BBAG For emptying dry chemical extinguishers without the mess.  
    Pail Bag PPB1 For controlling the flow while emptying pails.  
    Pail Opener PLO The right tool for opening pails without harming lid.  
    Rubber Mallet RM16 For many tasks, including closing pails.  
    Rubber Mallet RM16 For many tasks, including closing pails.  
    Dust Masks (50) RP9500 Fits over nose and mouth and has elastic head strap.  
    Bench Vise MBVD Fastens to bench and holds extinguisher firmly.  
    Nitrogen Regulator 2550 Regulates pressure for charging with nitrogen cylinders.  
    3-Way Valve 3WV Bleeds off pressure before removing quick-disconnect.  
    Valve Handle Grip VHG Squeezes lever to handle to keep extinguisher valve open.  
    Recharge Adapters RAKIT Contains 13 recharge adapters.  
    Hole Punch HP2 Hole-punch for service tags.  
    Hole Punch Holster HPH Keeps hole-punch handy on technician’s belt..  
    Utility Scale US100 Weighing extinguishers.  
    Leak Detector Fluid LD1 Applied to valve threads to determine leakage.  

    Always make sure you have a copy of NFPA 10, which contains the minimum requirements for safety and the service manuals that contain the procedures for recharging the extinguishers you work on. Knowing the code requirements and proper procedures for recharging and having the right tools and equipment for recharging will help ensure that your customer’s extinguishers are in proper working order in the event of a fire emergency. Also having a sufficient supply of recharge agent, tags, tamper seals, service collars, and the right tools will make your business more efficient and profitable.

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