Regarding the issue of testing pressure in the container first and then testing at 1.1 times the design pressure on-site for flaw detection
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This post was last edited by yxj197612 on 2016-8-23 at 14:45. I have a container designed for 20% RT; during the production process, a water pressure of 1.25 times the design pressure was used for testing. The customer requires that air tightness be tested at 1.1 times the design pressure upon arrival at the site. According to the code, the gas test pressure at 1.1 times the design pressure requires 100% RT. The company’s engineers believe that since the equipment has been subjected to a water pressure 1.25 times the design pressure, the stresses within the equipment’s cylinder have been redistributed under this pressure; as a result, the cylinder has expanded outward under the pressure and the process is complete. After that, when a pressure of 1.1 times the design pressure is applied, the equipment cylinder will not experience any further stress redistribution nor will it expand outward. Since the pressure from the air at this point is lower than the water pressure before, although it is 1.1 times the design pressure, it can no longer be considered part of the strength design; it can only be regarded as a process test ； Therefore, flaw detection can be carried out using water pressure; 20% RT is sufficient, and 100% RT is not necessary. I think it makes sense after hearing that, but I wonder what the experts think – is this approach reasonable? In other words, what should be done in the case of a container that is first tested under a water pressure of 1.25 times the design pressure, and then under an air pressure of 1.1 times the design pressure? Please analyze from the essence of the experiment: in this case, is 20% RT meeting the requirements?
The user requested that a leak test at 1.1 times the design pressure be conducted on-site. If this request was made along with the conditions chart, then I should carry out the leak test at 1.1 times the design pressure at 100% RT, as per the user’s request. If it is raised after the equipment arrives at the site, I believe a tightness test at the design pressure should be carried out as per the regulations. The airtightness should not be at 1.1 times the design pressure
This can be discussed with the user; if the client insists on conducting a airtightness test, it is recommended to reduce the test pressure to the design pressure, in order to meet the requirements of the Code for Solid and Pressure Vessels. Of course, since the hydrostatic test has passed, there should be no problem conducting a gas-tightness test at 1.1 times the pressure, and it is not necessary to carry out 100% radiographic inspection. And make it clear to the owner that, if pressure testing requirements are to be met, not only is radiographic inspection necessary, but welds of categories C and D also require 100% magnetic particle or penetrant testing, which is completely unnecessary. And the design drawings don’t specify any requirements for a gas-tightness test, right? Is it an additional requirement from the client?
Based on the conditions provided by the poster, it can be seen that this container is designed under conditions of partial non-destructive testing; therefore, using a design pressure 1.1 times higher for the so-called \"air-tightness test\" definitely violates the relevant container regulations. In my opinion, there is certainly no such provision in the design documents. If the contract signed by both parties includes a requirement for a \"air-tightness test\" at 1.1 times the design pressure, I believe the manufacturing unit should clearly inform Party A of the potential risks associated with this test. If Party A insists on carrying out this test, in order to protect the designers and the manufacturing unit, it is recommended that Party A issue a written document authorizing such an \"air-tightness test\". From a technical feasibility perspective, there is another issue: when conducting pressure-sealing tests at the site at pressures higher than those specified in the design, what should be done with the safety accessories (safety valves)? If the issue of safety attachments is avoided, is this test still meaningful?
:lolGB150 is written. . . For those that require a gas-tightness test, the test is conducted after the pressure test is passed, with the pressure used for the gas-tightness test being the design pressure of the container. This has nothing to do with the flaw detection ratio. . .
Why 1.1 times? There’s no need to make things so awkward. Since it’s airtight, there’s no requirement for such high pressure; in fact, a higher pressure only leads to disputes. Could we discuss with the client changing it to 1 time?
A design pressure of 1.1 times is equivalent to a pneumatic test; of course, 100% RT testing of the equipment is required. So it’s still necessary to discuss this with the customer. It’s not a matter of whether stress is redistributed or not, but rather whether the regulations permit it
This 1.i times pressure test has no practical significance; it would be better to conduct a airtightness test at the design pressure, while taking proper safety measures on site.
It depends on the drawings and the technical requirements of the designer; it’s not necessarily necessary to do everything exactly as the client requests
Isn’t 1.1 times the pressure used for a pressure test, rather than a test for airtightness?
The design itself does not require a pressure test; it was done at the customer’s request, just to show them, and it is not necessary to include it in the delivery documents.