What are the techniques and precautions (list) for pressure testing containers?
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What technical requirements and precautions must be met when conducting pressure tests on vessels such as exchangers, horizontal tanks, and towers?
Compared to hydraulic testing, pneumatic testing involves a high gas compression ratio, resulting in a high level of danger due to the stored energy; moreover, the explosion equivalent of pressure testing is high, posing significant risks. From the design stage, containers must take into account the strict requirements imposed by pressure testing on the toughness of materials, non-destructive testing of welded joints, and so on. The pneumatic testing plan must undergo strict approval, include a safety analysis and blast energy calculations, in order to determine protective measures such as isolation and enclosures. The testing process, voltage increase operations, etc., must be carried out strictly in accordance with standard specifications, with the voltage being increased step by step; attention must also be paid to the effects of environmental temperature, especially sunlight, on gas expansion, and so on.
For containers subjected to pressure testing or a combination of pressure and liquid testing, 100% non-destructive testing is carried out on their Type A and Type B joints. All relevant documents are reviewed before the pressure testing, and the testing can only proceed with the approval of the safety officer. Specified parameters include the testing medium, temperature limits, and testing methods.
What specific “technical requirements” should be specified in the design drawings? We currently have some heat exchangers in which the shell side consists of a container cylinder, while the internal tube side features coiled heat exchange tubes. Due to the extremely long length of these coiled tubes (nearly 100 meters), it is not feasible to conduct a hydrostatic test; after such a test, it is difficult to ensure that all water is removed. Therefore, an pneumatic test is generally used as an alternative to the hydrostatic test. Is it still necessary to conduct a airtightness test after the pressure test?
The most important thing is to increase the pressure slowly according to the standards and maintain it at that level (it is essential to do this in steps)
Generally, there is no need to perform a leak test again after adjusting the air pressure, except in special cases