Relationship between nominal pipe pressure and hydraulic test pressure
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The nominal pressure of a pipeline is determined by combining the design pressure of the pipeline, the design temperature of the medium, as well as other relevant regulatory requirements； The hydraulic test pressure for pipelines is 1.5 times the design pressure. So what is the relationship between the two? According to the veteran engineer, the hydraulic test pressure can be higher than the nominal pressure, but it cannot be too high; he was unable to provide a specific upper limit. Therefore, I’m seeking advice from everyone here. Thank you!
It’s available in Section 1 of Volume 1 of the \"Chemical Process Piping Handbook\". Hydraulic and pneumatic testing.
Thank you all! I still don’t understand the relationship between the hydraulic test pressure and the nominal pressure.
Nominal pressure is the pressure with a safety margin, while test pressure is the pressure that the equipment can withstand
Design pressure: Take the maximum value of P_set ≥ 1.1P_operation and P_set ≥ 0.1P_operation + 0.1MPa. Design temperature: When the operating temperature is ≤ 300°C, T_set ≥ T_operation + 30°C; when the operating temperature is > 300°C, T_set ≥ T_operation + 15°C. In low-temperature conditions, if T_operation ≥ -29°C, the design temperature is determined by process parameters; if T_operation < -29°C, then T_set = T_operation. Test pressure: P_test = 1.5P_set_test/P_operation, where test/operation ≤ 6.5. For your reference: lol
There is no inevitable connection between the two; the hydraulic test pressure may be higher than the nominal pressure. Definition of nominal pressure: It refers to the maximum operating pressure allowed for pipes and fittings at a reference temperature. As can be seen from this definition, the determination of nominal pressure relies on a reference temperature; for many types of steel used in China, this reference temperature is around 200 degrees. This value is higher than the temperature used during hydrostatic testing. Therefore, the maximum allowable operating pressure of a pipe during hydrostatic testing is higher than its maximum allowable operating pressure at 200 degrees (i.e., the nominal pressure). It is normal for the pressure calculated using the hydrostatic testing formula to be higher than the nominal pressure
For hydrostatic testing, it is sufficient as long as the pressure does not exceed the yield stress of the pipe. The yield stress of pipes made of common materials at room temperature is generally around twice the nominal pressure; you can look up the yield stress for the specific material in question. The yield stress of pipes with PN1.6 rating is roughly 3 MPa, so a hydrostatic testing pressure of 2.22 MPa should be fine as well
The hydraulic test is short-term; as long as the stress does not exceed the yield stress, there will be no problems