Inspection and Care of Fire Extinguishers

Inspection and Care of Fire Extinguishers

Industrial Fire Safety

Regretfully, users frequently find fire extinguishers inoperative because of inadequate inspection, maintenance and supervisory procedures. The records also show that the failure to make hydrostatic tests leads to injury, and sometimes death, to both users and service personnel.

There are rules for avoiding fire protection equipment failure, but many buyers and servicemen have little or no interest in reading instructions. Therefore, we will make recommendations for inspection, maintenance and hydrostatic testing in an attempt to assure extinguisher safety.

Inspections: A visual check should be made at least monthly and, if possible, weekly or daily if extinguishers are frequently used or are subject to tampering. This check should be recorded for each extinguisher on printed forms to show whether:

  1. Each unit is full. (Determine by checking gage pressure or hefting unit in place.)
  2. Seal is intact.
  3. Nozzle is unobstructed by either extinguishing agent or foreign objects.
  4. Hose and shell are undamaged.
  5. Extinguisher is in its proper place and unobstructed.
  6. Recharge record tag is attached and properly marked.

All extinguishers require at least annual maintenance or as dictated by conditions found during inspections. If extinguisher shells have dents or are corroded, they must be replaced to prevent possible injury to personnel. Please do not attempt repairs; replace these extinguishers. The nozzle, or horn, hose and connections must be replaced if they are physically damaged. Gages that are jammed or damaged in any way must be replaced, as it is vital to retain this pressure indication feature. Lock-down devices on valves, including safety pins, must operate freely and be in place.

Replacement of parts:Any nozzle shutoff valve that does not work properly should be replaced with a valve from the same manufacturer. Units with gas cartridges for expelling extinguishing agents require a careful check of the cartridge to see if it has been accidently punctured. It is also vital to check to see if the puncture device will work. If not, adjustments or replacement of the device is necessary. Any damaged or corroded gas siphon or pickup tube must be replaced.

If plant personnel do the maintenance work, you should obtain and require the use of manufacturers’ maintenance manuals for all extinguishers if personnel safety is a part of your overall plant goal.

It is recommended that 2 1/2-gallon soda-acid, foam and antifreeze extinguishers be discharged annually during fire brigade drills and then be recharged by following the manufacturer’s instruction on the label to the letter. The recharging should be recorded on the unit’s tag.

A carbon dioxide extinguisher must be recharged if its weight is more than 10 percent below the weight stamped on the valve assembly or the label. It is preferable to refill from a low pressure supply of carbon dioxide (300 psi at 0°F) rather than from a dry ice converter. CO2 extinguishers have no specific recharge interval.

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Industrial Fire Safety

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Dry chemical units discharged by a gas cartridge or large cylinder must have the cartridge replaced if it is underweight or the cylinder filled with nitrogen to the proper capacity, which requires special precautions. If the extinguishing agent is contaminated, underweight, overweight, or of the wrong type, then recharging is necessary. For dry chemical units of all types, the same chemical as was used originally should be used in recharging. In no case are different chemicals to be substituted, such as ABC dry chemical for sodium bicarbonate. There are great dangers involved in the mixing of chemicals as this can cause contamination, excess pressure and rupture.

Follow maker’s advice: Stored pressure dry chemical extinguishers should be recharged according to the manufacturer’s specifications if they are underweight, the gage is damaged, the seal is punctured or if there is any other valid reason. Dry chemical units have no specific recharging interval.

When recharging dry chemical extinguishers, it is important to keep shell interiors free of all moisture. This includes the chemicals used, as moisture can cause caking, making the extinguisher useless and dangerous to the user. For stored pressure dry chemical extinguishers, use only nitrogen for an expellant. Air from compressors can be contaminated by water and/or oil, which will foul the unit.

If it is necessary to replace a safety disk, be sure that the proper replacement is used. Do not substitute or make a disk from metal stock on hand.

Hydrostatic testing: One facet of extinguisher maintenance that is often ignored is hydrostatic testing.

The recommended hydrostatic test interval is no more than five years for the following types of extinguishers: soda-acid, cartridge-operated water, stored pressure and/or antifreeze water, foam, loaded stream, dry chemical with stainless steel, aluminum or soldered brass shells, and carbon dioxide. For dry chemical extinguishers with brazed brass or mild steel shells, and dry powder extinguishers with mild steel shells, the recommended test interval is 12 years.

If cylinder damage is apparent, tests should be made without delay, regardless of the test interval. DOT regulations should be checked.

If these tests are done on plant premises, you must have a hydrostatic test pump capable of 400 psi and a safety cage to hold extinguishers.

We also suggest you obtain Standard No. 10A, “Recommended Good Practice for the Maintenance and Use of Portable Fire Extinguishers,” for $1.00 from the National Fire Protection Association, 60 Batterymarch Street, Boston, Mass. 02110.

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