Hydraulic test pressure for high-pressure steel pipes
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For the shell-and-tube heat exchanger, the design pressure on the tube side is 32 MPa, and steel pipes in accordance with GB6479 are used. However, the GB6479 standard specifies that the pressure required for hydrostatic testing of such steel pipes should not exceed 20 MPa. How can this be explained? If the pressure used for the hydrostatic test is lower than the pressure experienced during actual operation, then what is the purpose of conducting a hydrostatic test?
A hydraulic test pressure of 20 MPa is merely a basic requirement specified in GB6479 for steel pipes leaving the factory; when manufacturing containers, the test pressure for the steel pipes must be determined based on their strength and design pressure.
You can ask the steel pipe manufacturer to increase the testing pressure; if they refuse to do so, you can purchase them and carry out the testing yourself.
Regarding the hydraulic testing issue when purchasing pipes, standard pipe specifications generally specify quantitative values for hydraulic testing. If the hydraulic testing requirements specified in your design documents are higher than those in the standards, you must provide the design values to the manufacturer. The principle is to take the higher of the two values. But you will have to pay an extra fee.