Hydrostatic Tank Testing

Hydrostatic pressure is the pressure exerted by a fluid that is not in motion. Hydrostatic testing is commonly used to test storage tanks and cylinders -- such as industrial storage tanks and self-contained breathing apparatus (SCBA), as used by emergency service workers and divers -- for leaks or flaws.

SCBA

In the case of SCBA tanks, hydrostatic testing involves filling the tank with an almost incompressible liquid -- typically water -- at 150 percent of normal operating pressure and testing for leaks or permanent physical deformation of the cylinder. Water can only expand by a small amount and is significantly safer than compressed gas, which can expand rapidly, possibly causing serious injury.

Specific Gravity

Industrial storage tanks are hydrostatically tested by filling with water to the maximum level for which they were designed. If brackish or salt water is used for testing, the load placed on the tank is higher than if fresh water is used; the specific gravity of salt water is 1.3, compared to 1.0 for pure water, so it is effectively heavier.

Contaminants

Certain types of storage tank, such as those made from stainless steel, are more susceptible to contaminants than others. The water used to hydrostatically test these types of tank should be analyzed for pH and the presence of corrosive elements, such as chlorine.

References

• LSS: Hydrostatic Testing of SCBA Cylinders
• "Guide to Storage Tanks and Equipment"; Bob Long, Bob Garner; 2004