Can the set pressure of a safety valve be reduced from a higher value to a lower one?
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There is a safety valve whose set pressure is 1.36 MPa, and its cold set pressure is 1.3736 MPa. I would like to change it to a set pressure of 0.8 MPa. Is this possible? If possible, what standards are followed? **Is it allowed by the standards? Thank you all.
It should be possible. The safety valve has a nominal pressure; as long as the pressure doesn’t exceed that value, there’s no problem. Additionally, if the setting pressure is low, the valve may open more frequently.
It will be fine as long as the operating pressure of the system you are installing does not exceed the nominal pressure specified for the safety valve. You can check that the set pressure is approximately 1.17 or 1.2 times the system pressure, and this includes the start-up pressure and the return pressure
What kind of pressure is the nominal pressure? The design specifications do not specify the nominal pressure; it is only known that the flange is 300 pounds. Is it the design pressure? Thank you!
First, does your process require it?； Secondly, it is acceptable to report to the supervisor if the process requires it.
300 pounds is the nominal pressure.
It’s possible; it cannot be operated by oneself – it is handled by the security and metrology departments. It must also meet the process requirements and safety standards of the system equipment.
Well, we don’t carry out this operation by ourselves; we take it to the metrology department for calibration. Thank you!
It cannot be changed arbitrarily; it must be approved by the design institute and the manufacturer. The calculation of the rated discharge capacity of the safety valve is related to the set pressure.
If the operating pressure changes and needs to be adjusted, a design change is required; otherwise, all kinds of approvals cannot be obtained.
Safety valves usually need to be handled at a calibration institute.