Hydrostatic testing is the most commonly used way of testing strength and leaks in hoses and pipes, and is also a safer way to test than the alternative pneumatic testing. The test is often needed after shut downs and repairs, to make sure that the equipment is valid to operate under the required conditions once it begins service again.
Hydrostatic testing cannot take place whilst normal operations are ongoing, and cannot monitor for leaks after the test has been performed. On-stream hose/pipe integrity is best controlled by an effective equipment mechanical integrity program.
Hydrostatic testing is considered to be a form of non-destructive testing – meaning it won’t damage any equipment in its process. However, if a specified pressure is exceeded or there is a small crack, equipment can end up rupturing and failing.
Hydrostatic testing is a common method for resting industrial hoses such as the rubber hose, pvc hoses, and steel hose assemblies.
How does hydrostatic testing work?
Hydrostatic testing is a form of pressure testing which works by completely filling the hose or other component with water, removing the air contained, and adding pressure to the system that is up to 1.5x higher than the pressure limit.
The pressure is then held in the unit for a period of time so it can be visually inspected for leaks. These inspections can be enhanced by adding tracer or fluorescent dyes to the water to make the cracks or leaks more apparent in their origin.
Common Methods of Hydrostatic Testing
There are three different common methods of hydrostatic testing methods that can be used. This includes the water jacket method, the direct expansion test, and the proof testing method.
The Water Jacket Method
In order to perform this method, the vessel is completely filled with and loaded into a sealed chamber called a ‘test jacket’ that is also filled with water. Pressure is then added to the vessel whilst inside the jacket for a period of time. This leads to the vessel expanding inside the test jacket, and pushes water out of the test jacket and into a glass tube. This measures the total expansion of the vessel.
Direct Expansion Method
The direct expansion method of hydrostatic testing involves filling the vessel or cylinder with a specific amount of water, then adding pressure to the system, and measuring how much water is let out once the pressure is returned to normal.
Proof Pressure Method
The proof pressure method of hydrostatic testing adds pressure internally and determines if the vessel or hose contains any leaks or other weaknesses like wall thinning that could cause failure.