Will a stored pressure fire extinguisher's dry chemical agent compact?

November 1, 2023

NO! In fact, a case can be made that quite the opposite is true.

Consider this:

Stored-pressure fire extinguishers have pressure being exerted in ALL directions within the vessel, not just from the top. This actually helps to keep the chemical fluidized during storage and compaction tests (this is also the reason for always pressurizing units through the valve and down tube).The pressurizing gas is present between dry chemical particles and when the valve is opened, the pressurizing gas expands – instantly fluidizing the dry chemical.

ALL UL listed extinguishers are subjected to vibration and compaction tests regardless of the design. These tests are meant to try to compact the dry chemical so it won’t discharge. All Amerex stored-pressure extinguishers pass these tests and BSI (British Standards), EN3 (European Standards) and Australian and a host of others.

Cartridge operated extinguishers are not under constant pressure and as a result:- They can be tampered with, (fill caps loosened, cartridges loosened, hoses loosened), and the chemical may be compromised with moisture or foreign objects. They depend upon gas going through a tube and a series of ports and check valves. If this gas tube is not removed during hydro-test you will certainly develop a block. It may also get blocked from chemical moving into the tube if it is not checked during annual maintenance.

No gas distribution system design in a cartridge operated extinguisher will fluidize caked chemical, nor will a stored pressure extinguisher operate correctly with caked chemical. Cartridge operated extinguishers, by design, are more susceptible to moisture intrusion than stored pressure extinguishers.

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