Pressure testing ofsmall air separation unit and piping systems requires pressure testing in different sections, divided into two sections: inside the cold box and outside the cold box.
Pressure test of the internal piping of the cold box: the system is tested by air pressure and the medium is dry, oil-free air. The test must be carried out by a dedicated partition responsible for strictly and carefully checking the leakage of each part, no leakage is allowed. The test pressure, stopping time and residual rate of each system are specified according to certain requirements. The pressure filling procedure is divided into two steps:
1, the first pressure filling to 20kPa, check the weld flange and other removable connections have no obvious leakage, if there is a leak, then release the pressure to fill the leak or tighten the removable parts;
2, after the above processing and then pressure filling to 50kPa and then carefully checked. If there is still leakage, the pressure should also be released to deal with it; then increase the pressure to 50 kPa. when there is no leakage, gradually increase the pressure to the test pressure specified in Table 3 -12.
The test must be carried out strictly in accordance with the division of labour in the pipeline to check for leaks. Leak detection can be carried out with non-fat soapy water or dibutyl sodium caisulphate solution as a foaming agent (as it has a corrosive effect on aluminium, it should be scrubbed clean with clean hot water after the leak test). Leaks in welds must be repaired correctly. Repair by tapping or by using a preservative (low temperature adhesive) is never allowed. The repair weld is then checked with 50kPa pressure.
Pressure test of the external piping of the cold box: except for the pressure test of the water system which can be carried out with water, the rest of the system is carried out according to the above requirements.
After the pressure test, the blind plate for the test pressure is removed and a new gasket is fitted to tighten the bolts and nuts. After removing the blind plate, another gas tightness test is required, with the test pressure being the working pressure.
Dear Air Separation carries out pressure tests on small air separation unit and piping systems, according to its own technical requirements, and follows the relevant pressure test procedures to ensure the quality.
