How is the test pressure determined for testing each heat exchange tube in a shell-and-tube heat exchanger individually?
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GB151 specifies clear test pressures for U-tube heat exchange tubes with butted welds, as well as for heat exchange tubes that are tested individually. However, no basis could be found for the test pressure of tube bundles without seams when tested individually.
What I want to ask is how to determine the specific value of the test pressure
Hydraulic testing can be carried out on each heat exchange tube in accordance with the corresponding pipeline material standards; the hydraulic testing method is GB/T241
Hydraulic testing can only be carried out one by one
The test pressure is the highest of the test pressures for either the tube side or the shell side, as stated in 151
Conduct tests one by one according to the response coefficients of the maximum design pressure of the heat exchanger
For the test pressure of individual heat exchange tubes, aside from those specified in 151, the values for the rest can only be estimated using the formulas in 9948 or 13296, or even the formula in NBT47019; the maximum value shall not exceed 20 MPa
This is a hydrostatic pressure applied to the material itself
As for why the hydrostatic pressure for single heat exchange tubes is specified at 151, my understanding is that bending or joining such tubes may damage their original material condition and affect their properties; whereas for the other heat exchange tubes, it is sufficient for them to meet the relevant standards for heat exchange tubes (the impact of welding the heat exchange tubes to the tube sheet on their properties is not considered here)