Hydrostatic Testing of Compressed Gas Cylinders
Hydrostatic testing is the most common method employed for testing cylinders. A hydrostatic test is a way in which pressure vessels such as gas cylinders can be tested for strength and leaks. The test involves filling the cylinder with water and pressurization of the cylinder to the specified test pressure.
Newly manufactured cylinders are initially qualified using the hydrostatic test. Cylinders are then requalified at regular intervals according to Canadian standards. Testing of cylinders is very important because such containers can explode if they fail under pressure.
The test system is calibrated daily prior to running production. Prior to being tested hydrostatically a cylinder must pass internal and external visual inspections. The cylinder is then tested in a water jacket in which it is pressurized to its specified test pressure, and held for 30 stable seconds, and the volumetric expansion (VE) is measured by an expansion indication device (EID) that measures the amount of liquid that has been forced through the expansion line into the EID by the volume increase of the pressurized cylinder in the sealed water jacket. The cylinder is then depressurized and the permanent volumetric expansion (PVE, i.e., the permanent volume increase of the cylinder due to deformation while under pressure) is measured by comparing the final volume in the EID with the volume before pressurization.
The information needed to specify the test requirements is stamped onto the cylinder’s shoulder. This includes regulating authority, a design standard/specification, serial number, manufacturer, manufacture date, and sometimes other relevant information. If the cylinder fails, it will go through a condemning process which shall prevent any further use. Cylinders that pass the hydrostatic test are stamp marked on their shoulder with the date of the successful test and the test facility’s registered mark.
The required testing frequency is as follows:
- TC-3ALM/DOT-3AL gas cylinders must be tested every 5 years
- TC-3AAM/DOT-3AA gas cylinders must be tested every 5 years, unless stamped with a star (*) following it’s most recent test date in which the cylinder met certain specifications allowing it to be tested every 10 years
- TC-3FCM, TC-3HWM, TC-3CCM gas cylinder must be tested every 5 years and have a limited life of 15 years from the date of manufacture
- ISO9809-1 gas cylinders must be tested every 10 years
Our facility performs hydrostatic tests using the Galiso Rec4 Open.
