Discussion on pipeline design pressure
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Does the design pressure of a pipeline need to take into account the operating pressure during purging? For one of my pipelines, the normal operating pressure is at atmospheric level; does the design pressure need to consider purging? For example, in the case of an atmospheric vent pipe for me, does the design pressure need to take purging into account?
As long as there is a design pressure, no matter what you do, you must operate under the control of this pressure. To test the pressure, tests are carried out at the specified water and air pressures (see the relevant requirements for test pressures). There are specific regulations for low-pressure pipelines such as those used for gas, and the specified test pressures are higher than the operating pressures (see the relevant provisions).
For atmospheric pressure pipelines, the design pressure is usually set at 0.1 MPa. Vent pipes connected to the atmosphere will not cause pressure buildup.
The purge pressure is 0.7 times the design pressure, and it is independent of the operating pressure.
The determination of the design pressure is related to the following conditions: 1. Normal operating pressure; 2. The highest working pressure that may be reached during pipeline operation. The design pressure must be higher than the highest working pressure in order to ensure stable operation and the safety of pipeline accessories. Depending on the specific circumstances, a fixed value or a certain percentage is added to the highest working pressure. Maximum operating pressure: This can be the purging pressure, the highest pressure generated by the power sources for the pipelines (pumps, compressors, etc.), or it can also be the shut-off pressure resulting from valves closing accidentally or failing. When making choices, some are based on standard requirements, while others rely on empirical values. For example, in the case of purging: if one uses the pressure and temperature values associated with the purging line, those values turn out to be too high; in reality, such temperatures and pressures cannot be achieved, so experience plays an important role here.
The design pressure of the pipeline does not need to take into account the operating pressure during purging
It is generally not necessary, as the maximum pressure that a pipe can withstand can be determined by using its wall thickness. With a wall thickness of 1 mm, the allowable pressure level is very high, and it will already cover the pressure associated with purging