The Water Jacket Test Method

First the cylinder is visually inspected.  Both the exterior and interior of the cylinder are carefully inspected for any defects the could affect its performance.  Of course the valve is removed before the interior is inspected.

Upon satisfactory completion of the visual inspection  the cylinder is filled with water and a test adapter is threaded onto the cylinder and attached to the test plate.  (Note: Temperature is very important.  The cylinder, water and air temperature need to be relatively close to each other, about 5 degrees, otherwise the test result could fail the cylinder when it should have passed and visa virca.)

Before being lowered into the water jacket all pertinant data is recorded.  After the cylinder is lowered into the water kacket and clamped shut, all the air is vented from the system.  At this point the cylinder is completely full of water and completely surrounded by water.  

More water is pumped into the cylinder to pressurize it to the predetermined test pressure.  

As this happens the cylinder will expand pushing the water out of the water jacket which is measured for total expansion.  Pass or fail is determined by the test requirements of the cylinder being tested.

After passing the hydrotest the cylinder is dried with hot forced air, inspected again and marked as having passed testing.  Some cylinders and stamped with the test date and others have a label affixed and overcoated with epoxy.