Change hydraulic testing of equipment to pneumatic testing
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This post was last edited by Paris on 2022-9-7 at 16:25. I’d like to ask everyone a question: There is a tower-type vessel with a relatively large diameter, thin walls, and very low operating pressure. After its manufacture, it was scheduled to undergo a pressure test at the factory. The design institute specified a hydraulic test in the blueprints. However, the factory considered that a hydraulic test would require a large amount of water; moreover, after being filled with water, the shell might deform when placed on a rotating fixture. Additionally, creating special fixtures for the test would be quite costly. Therefore, the factory requested permission from the design institute to switch to a pneumatic test instead, with the test pressure being adjusted accordingly (100% radiographic testing is required for all longitudinal and circumferential welds). Eventually, the design institute agreed to this change, while reminding us to take appropriate protective measures. I’d like to ask everyone: 1. Should this adjustment from hydraulic to pneumatic be made on the as-built drawings? 2. If the drawings are changed, should the calculation sheet also be adjusted? (The stress verification results for hydraulic testing and pneumatic testing are different.) 3. Should the nameplate indicate the value based on hydraulic pressure or pneumatic pressure? 4. Do the standard specifications provide any guidelines on how to handle this situation specifically? (PS: I’ve encountered similar situations a few times, and the responses we were given varied quite a bit. ）
1. The hydrostatic test pressure specified in the as-built drawings must be changed to a pneumatic test pressure. 2. The calculation sheet definitely needs to have the pneumatic test pressure updated, and it should be verified whether this value meets the requirements； 3. The nameplate definitely indicates air pressure, not hydraulic pressure ； 4. The designer of the drawings must issue a change order; based on this change order issued by the designer, the manufacturer is required to make the corresponding adjustments ； 5. After changing from hydraulic to pneumatic pressure, A, B, C, and D must undergo 100% surface inspection (magnetic particle testing for ferromagnetic materials; penetrant testing for the rest)
As I recall, this happened three times. It seems that only once did the design institute request that the nameplate also be changed to reflect the pneumatic test. In the other two instances, neither the client nor the design institute asked for any changes to the nameplate. However, in that one instance when the nameplate was changed, the design institute still didn’t provide us with a new calculation sheet; the as-built documentation continued to use the original hydraulic calculation sheet. Our manufacturing plant simply follows the requirements set by users and design institutes; if they ask us to make changes, we do so; otherwise, we don’t make any changes. There’s no other evidence either.
Once a change order is issued, it must of course comply with the regulations, and all relevant parts and information should be updated according to the changes
Due to the transition from hydraulic to pneumatic design, the design institute needs to revise the calculation documents, adjust the relevant technical requirements, and modify the technical specifications in the drawings; for Category III projects, a risk assessment report also needs to be revised. Accordingly, the as-built drawings and nameplates must be altered as well