External Maintenance of Dry Chemical Extinguishers

External Maintenance of Dry Chemical Extinguishers 
by Mark Conroy, Sr. Engineer for Technical Services, Brooks Equipment (July, 2010)

Most handheld portable fire extinguishers in buildings are rechargeable, stored-pressure dry chemical extinguishers. These extinguishers require annual external maintenance examinations. An internal maintenance examination is only required at the 6-year maintenance interval and the 12-year hydrostatic test interval. The cycle of external maintenance, internal maintenance, and hydrostatic testing is repeated for the service life of the extinguisher to ensure the safety of the user and the reliability of the device.

Annual external maintenance of these extinguishers is necessary so that a number of critical components can be examined and repaired (if necessary) in order to make the fire extinguisher ready for use during a fire emergency. Where repairs are not appropriate, the extinguisher is replaced. When the external maintenance is performed correctly and completely on an annual basis and internal maintenance and hydrostatic testing are conducted on schedule, the maximum level of assurance that the extinguisher will work (as designed) to suppress or extinguish an unwanted fire is provided.

The responsibility for establishing a contract for portable fire extinguisher maintenance falls on the building owner, the owner’s designated agent or the tenant of the building where fire extinguishers are located. Once the contract is established, performing maintenance correctly and at the right intervals normally is the responsibility of the fire equipment distributor. The actual task of extinguisher maintenance is assigned to a technician that understands how to examine the extinguishers and to take any necessary corrective action.

The technician performing the maintenance relies on the extinguisher manufacturer’s service manual for specific information on external examinations. The manuals also contain cautions and warnings so that the technician performs the tasks safely. Generally, the same external examination procedures are followed for all rechargeable, stored pressure dry chemical extinguishers. The practice has been standardized and the complete list of items to be examined has been added to the 2010 edition of NFPA 10, Standard for portable Fire Extinguishers.

General procedures for Annual External maintenance

The extinguisher is removed from the hanger or cabinet and checked for damage. A broken or deformed verification f-service collar indicates a suspect extinguisher that must be taken out of service for full maintenance, which includes internal examination. The hanger must be the one designed for the extinguisher. If it is identified as the wrong hanger or is damaged, the hanger is replaced. Extinguisher height and hanger mounting hardware are also examined. Incorrectly installed or loose hangers are removed. The hanger must then be properly located and securely re-attached at the correct height. Cabinets are checked for damage and proper operation. Auxiliary components such as “break glass devices” must be checked to make sure they are the proper ones for the cabinet and readily available for use.

The operating instructions label on the extinguisher is examined to confirm that it is the right one and it is securely attached to the extinguisher. The label must not be faded and must be in a condition in which it is clearly legible and will not come off easily. Also, the location of the label is evaluated to make sure the instructions will be facing outward when the extinguisher is returned to its hanger or cabinet. Problematic operating instructions labels are replaced.

Any extinguishers that are subject to recall or have become obsolete due to safety concerns are removed from service. Extinguishers that are considered obsolete are listed in Section 4.4 of NFPA 10.

The service technician reviews the maintenance and hydrostatic test records. Any extinguishers due for the 6-year teardown or hydrostatic testing are removed so that the work can be done. Any fire extinguisher that is removed from a building for repair, internal maintenance, or hydrostatic testing must be replaced by a fire extinguisher that is appropriate and rated for the hazard.

A thorough examination of the condition of the extinguisher cylinder is conducted to check for corrosion, dents, gouges, and repairs. If corrosion, dents, or gouges are identified, an evaluation is made to determine whether the problem areas are within tolerable ranges or whether the extinguisher needs to be replaced. Tolerances for corrosion, dents, and gouges are provided in NFPA 10. Any extinguisher that shows signs of being repaired such as welding is replaced.

An evaluation is conducted as the pull pin is being removed. A pin that does not slide out easily is replaced. Additionally, the pin and the slot are examined. A bent or corroded pin is replaced. With the pin out, the valve stem is examined to make sure that it protrudes out the top of the valve and is correctly extended. The valve stem is also checked for corrosion and damage. A valve stem problem typically necessitates the teardown of the extinguisher and the replacement of the valve stem.

The handle and the actuation lever are examined. Bent or corroded handles or levers and rivets that cause the lever to stick are reasons for extinguisher removal for repair. A new tamper seal is installed when the pull pin is inserted in the extinguisher lever. The new tamper seal is not only required, but it gives the building owner or a fire inspector a visual indication that the pull pin, valve stem, handle, and lever evaluations were most likely conducted during maintenance.

The pressure gauge is checked to make sure the needle is in the operable range. The pressure gauge is examined to ensure it is not damaged or bent, or the face plate cracked. The technician also confirms that the pressure gauge matches the agent type and the nameplate’s operating pressure and verifies the gauge threads are compatible with the valve body material. An extinguisher with a problematic gauge is removed for replacement of the gauge.

The extinguisher hose is removed and examined for cracks or deformation. The technician verifies that the hose is the correct one for the extinguisher model and that the hose assembly has no obstructions. Additionally, the condition of the hose assembly threads and couplings is assessed. While the hose is off, the valve port surfaces are examined for signs of leakage or corrosion that indicates the need for a tear down to correct these problems. Any improper, cracked, clogged or otherwise problematic hoses are replaced. The extinguisher must have a hose in good condition installed with one end fastened securely to the valve and the other end in the hose retention band that is securely and properly adjusted before it is returned to service.

The extinguisher is weighed to verify the weight corresponds to the nameplate weight. A lower weight indicates a problem that necessitates recharging of the extinguisher. After the proper weight has been verified, the extinguisher is wiped clean of any dirt and contaminants. The maintenance is recorded on a new extinguisher tag or label, and the extinguisher is replaced on the hanger or returned to the cabinet.

Ready For Use!

Once the external maintenance is complete, the extinguisher is ready for use during a fire emergency. When periodic maintenance and hydrostatic testing are conducted correctly during the required regular intervals, the probability that the extinguisher will work as designed to suppress or extinguish an unwanted fire is maximized.

The above article is the opinion of the author and does not necessarily represent the position of a NFPA technical committee or the NFPA and may not be considered to be or relied upon as such. Mark Conroy is an engineer with Brooks Equipment Company and a principal member of the NFPA Technical Committee on Portable Fire Extinguishers. Copyright 2010, all rights reserved.

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Posted in Life Safety, Portable Fire Extinguishers

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