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Aug 26, 2013

WHAT IS HYDROSTATIC TESTING?

WHAT IS HYDROSTATIC TESTING?

Hydrostatic testing is the most common procedure used to qualify newly manufactured cylinders, spheres and tubes used for the transportation of dangerous goods.
Hydrostatic testing is also required periodically to re-qualify these pressure vessels for continued service.
During a hydrostatic test, a pressure vessel is placed inside a closed system, usually a test jacket filled with water, and a specified internal water pressure is applied to the container inside this closed system. The applied internal pressure causes an expansion of the container being tested, and the total and permanent expansion that the container undergoes are measured.
These volumetric expansion  measurements, in conjunction with an internal and external visual inspection of the container, are used to determine if a pressure vessel is safe for continued use, or has suffered from a degradation in its structural integrity and must be condemned.
Some pressure vessels may be re-qualified by means  of a proof-pressure test. This method, also known as a modified hydrostatic test,  consists of subjecting a pressure vessel to a specified internal pressure and inspecting the pressurized container for leaks, bulges or other defects. This method is permitted only when the applicable regulations do not require the determination of volumetric expansion measurements (e.g. for certain types of low pressure cylinders such as those used on many portable fire extinguishers).


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