Hydrostatic Cylinder Testing

Water Jacketed Method

In the water jacketed method of testing, a cylinder, filled with water, is placed inside a sealed chamber (test jacket) and pressure is applied. Due to the pressure, the cylinder expands and certain amount of water is displaced. A calibrated tube or a burette is connected to the jacket to measure the amount of displaced water. The cylinder is then deflated. When the cylinder regains its original shape the displaced water collected is drained. Most of the time the cylinder does not return to its original size and is stretched due to pressurization. This is called permanent expansion. The difference between permanent expansion and total expansion is called elastic expansion.

Percentage Expansion = (Permanent expansion/Total expansion) * 100

Non Jacketed Method

The non-jacketed method or the direct expansion method, involves measuring the unpressurized volume of the cylinder. During this test, the cylinder is pumped with water until the required pressure for the test is obtained. The results achieved are similar to the water jacketed method, but is less accurate since air can be trapped during the process. To avoid this error, it is necessary to fill the cylinder completely with water. When the cylinder regains its original shape, the displaced water collected is drained.

For Gases & Liquids