Hydro-Static Testing

Almost all packages containing hazardous material are required to be pressure tested.  The U.S. Dept. of Transportation (D.O.T.) considers any package containing a non flammable compressed gas which exerts 41 PSI or above at 68º to be considered hazardous material, and is required to pass a pressure test at specific intervals for the package to remain in service.  A fire extinguisher cylinder (the package) falls under this requirement.

Depending on the type of material the cylinder is made of and the pressure inside will dictate the required test pressure and test intervals.  Simply a hydrostatic test is a pressure test on the cylinder to verify it is still safe to be kept in service.

 

Hydrostatic testing consists of depressurizing the cylinder, removing the contents and performing a visual inspection of the cylinder inside & out.  Looking for evidence of corrosion, mechanical damage, evidence of exposure to a fire, or anything of the like, which could weaken the cylinder.  After the cylinder passes the visual inspection, it is filled with a liquid (typically water) and the specified pressure is applied and held for the required test time.

 

If the cylinder shows no signs of leakage, bulging or excessive permanent expansion, it passes the hydrostatic test.  It is then emptied and dried and the appropriate markings are applied to the cylinder indicating it has successfully passed its required testing.  The cylinder is now approved to be refilled & pressurized as needed, until the next required test.