When determining the nominal pressure of a pipe flange, should the pressure used for testing be taken into consideration?

In my personal opinion: it’s not necessary.

It is necessary; hydraulic testing must be taken into account, and your design pressure must be higher than the pressure used in the hydraulic test. It is explained in the Chemical Process Design Manual

I don’t think it’s necessary. All fittings and the like are subjected to hydrostatic testing at a multiple of the design pressure (such as 1.5).

It is necessary; generally, the design pressure is higher than the hydrostatic test pressure

Generally speaking, without considering corrections for temperature effects, the nominal pressure of pipe flanges is >= design pressure >= maximum operating pressure. A coefficient must be applied when determining the hydrostatic test pressure for pipe flanges, and the same coefficient (such as 1.5) must also be used when determining the hydrostatic test pressure for the pipes themselves. Therefore, when determining the nominal pressure of pipe flanges, there is no need to take the test pressure into account. The correction considering the temperature effect follows the same principle. On the 3rd floor, it’s necessary to consider hydraulic testing; your design pressure must be higher than the pressure used in such testing. The “Chemical Process Design Manual” states this, so it’s clear that it must be wrong without even referring to that manual. The hydrostatic test pressure should definitely be above the design pressure.

The 6th floor is correct; it’s the same as with pressure vessels. The pressure used in hydraulic tests is always higher than the design pressure, as the hydraulic pressure is generally equal to the design pressure multiplied by a coefficient. For vessels, this coefficient seems to be 1.3 times the temperature correction factor, while for pipes it’s 1.5. The temperature correction factor also needs to be taken into account

It’s not necessary; as long as purchases are made in accordance with the design standards, there’s no need to consider the test pressure, as it is already included in those standards

No need, the guy on the 6th floor explained it very clearly. Moreover, the test pressure for pressure testing is determined based on the design pressure; that is, the design pressure multiplied by a corresponding coefficient equals the test pressure. The test pressure has no direct relationship with the maximum operating pressure, and it is necessarily greater than the design pressure.