Is it necessary to pressurize the root valve for instrument pressure tapping?
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As the title suggests, for ordinary instruments, the root valves (such as pressure gauges and transmitters) are typically classified under the process category in the installation drawings. Recently, for one installation, the design specified that the root valves should be considered part of the instrumentation side (at the P/I boundary); the quantity required is listed in the material sheet, with only DN15, DN50, and DN80 available. The client then asked our instrumentation team to carry out pressure testing before installation. I would like to know if there are any standards that specify whether pressure testing is necessary or not Because in the past it was all handled by the craftsmen; they would suppress things and carry out the installations. Moreover, several standards were consulted, all of which deal with valves installed on pipelines; does the same apply to the root valves of instruments as well? I seek help from experts to resolve this issue.
First of all, you should take responsibility for what you have acknowledged. But looking at the specifications of this valve as a root valve for instruments, it’s really too large, isn’t it? If you think and guarantee that it’s not necessary to suppress it, then it’s fine. As long as it doesn’t leak when in use, that’s fine. However, for valves of such a large diameter, it is indeed safer to apply pressure to them; even if pressure is applied, there is no guarantee that they will not leak during use. Just press down according to the specifications. It would be best if all three parties – the two involved and the supervisor – give their approval on-site, to avoid having to deal with issues that arise during testing later on. This includes leaks caused by non-instrumentation personnel during use.
It is caused by unclear boundaries in the division of responsibilities for design and construction
This seems unnecessary....
This is complete nonsense; it’s simply a mismatch between the manufacturing process and the instruments, with poor coordination! The main pipelines and equipment need to be pressurized to ensure airtightness, and the root valves of the instruments only need to be checked at the same time as the main pipelines and equipment are pressurized and made airtight. After the process engineers supply the pressure medium, the instrument technicians can then check each valve one by one. After all, these valves will be used by the instrumentation team in the future, so the process engineers cannot help with the inspection; any internal leakage in the valves will affect the instrumentation team as well.
It needs to be suppressed, and pressure testing should be carried out along with the main equipment pipeline. The hydrostatic test pressure is raised to 1.5 times the design pressure.
The first root valve in the process pipeline needs to be pressurized, whether it is from the process engineering team or the instrumentation team. If the first root valve leaks during production, it is necessary to shut down the plant, resulting in significant losses. The measurement pipelines in the instrumentation field also require pressure testing for leaks, but in this field, the testing is carried out on-site after installation.
I’ll send you a copy; take a look for yourself. I encountered a similar situation before: it was installed, then removed and taken out for compression.
After discussing it with the project team, we will provide the labor force, while the workshop will handle the fitters; compression is still required