High pressure gas storage cylinders are subject to a hydrostatic pressure test every five years . The date of successful test is stamped on the neck of the cylinder next to the original test date.
Trained staff will always check dates before refilling๐
In my extensive aviation experience, the only lubricant permitted was distilled water.
Periodic pressure testing also applies to LPG cylinders used to supply cooking gas all over Thailand. When was the last time you checked the test dates on yours?๐