(1) The air tightness test is to be carried out after the hydraulic test is passed. For pressure vessels whose design requires air pressure test, the air tightness test can be carried out simultaneously with the air pressure test, and the test pressure should be the pressure of the air pressure test.

(2) For pressure vessels made of carbon steel and low-alloy steel, the temperature of the test gas shall not be lower than 5°C, and for pressure vessels made of other materials, it shall be specified in the design drawings.
(3) The gas used in the air tightness test is to be dry and clean air, nitrogen or other inert gases.
(4) When carrying out the air tightness test, the safety accessories should be fully installed.
(5) The pressure should rise slowly during the test. After reaching the specified test pressure, the pressure should be kept for no less than 30 minutes, and then lowered to the design pressure. Brush soapy water on all welds and joints for inspection, and it is qualified if there is no leakage. If there is any leakage, perform hydraulic test and air tightness test again after repairing.