Determination of the design pressure for ultra-low pressure pipelines

At 0.03 MPa and room temperature, ordinary pipes can meet the standards. The pressure doesn’t need to be determined, right? It is sufficient to mainly determine the pipe material. The corresponding valve should be one with a normal pressure of 1.0 MPa or 0.6 MPa, right?

Article 3.1.2 of the Code for Design of Industrial Metal Piping stipulates that the design pressure shall be determined in accordance with the following requirements: 3.2.2.1 The design pressure of a pipeline and each of its components shall not be less than the pressure under the most severe conditions resulting from the combination of internal or external pressures and temperature encountered during operation. The most severe conditions should be the parameters corresponding to the maximum thickness and highest nominal pressure required for the pipe components in the strength calculation. However, the design pressure mentioned above shall not include the occasional pressure variations permitted in this chapter. 3.1.2.2 For pipelines under the following special conditions, their design pressure shall be compared with that specified in paragraph 3.1.2.1, and the higher of the two values shall be adopted. (1) For pipes transporting fluids with low vaporization temperatures such as refrigerants and liquefied hydrocarbons, the design pressure shall not be less than the highest pressure that can be reached due to vaporization at the highest ambient temperature when the valve is closed or the fluid is not flowing. (2) The design pressure of the outlet pipe of a centrifugal pump shall not be less than the sum of the suction pressure and the pressure corresponding to the head. (3) For pipes that lack pressure relief devices or have such devices that are isolated, the design pressure shall not be lower than the maximum pressure that the fluid can reach. 3.1.2.3 Vacuum pipes shall be designed to withstand external pressures; when equipped with safety control devices, the design pressure shall be 1.25 times the maximum difference between internal and external pressures, or 0.1 MPa, whichever is lower ； In the absence of safety control devices, the design pressure shall be 0.1 MPa. 3.1.2.4 The design pressure of pipelines equipped with pressure relief devices shall not be less than the pressure at which the relief devices operate. In practical design, some use 1.1 times the operating pressure, while others use the operating pressure plus 0.18; this is for reference only. The system you are referring to is a slightly positive-pressure system; in fact, for any given pipe material, the pressure will be much higher than that in the operating condition you mentioned. This post was last edited by dreaming on 2009-3-11 13:25.]

It seems there’s a requirement that the pressure used for testing must not be lower than 0.2 MPa

It cannot be lower than 0.4MPA