Understanding MAWP and High-Pressure Vessel Design

This white paper explains how and who determines the maximum allowable working pressure (MAWP), the relationship between MAWP and Design Pressure, and finally how high-pressure vessel is designed. It specifically looks at how ASME VIII Division 1 formulas that account for the thickness of various vessel parts, such as longitudinal and circumferential force formulas, have evolved. It is discussed within the context of structural material properties that can affect high-pressure design and considers three common types of high-pressure vessels to provide engineers with how MAWP is determined and its potential limitations. 

Consider how the circumferential forces in a thin cylindrical shell due to internal pressure affects the thickness of the shell. In the above figure, the internal pressure acts on the projected area formed by the diameter, D, and the length, L, of the cylinder. The force generated as a result of this pressure acts circumferentially and tends to increase radius and tear apart the cylinder along the axis. This is how a cylinder filled with liquid fails when subjected to thermal expansion. We know that pressure is force per unit area. Therefore, this force is thus calculated by [calculation]. The allowable stress, S, of the material of construction of the vessel at the design temperature that opposes the tearing by the pressure acts on the two longitudinal areas, each Lt units, of the vessel. The opposing force [calculation].

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