Classification of high, medium, and low pressures in chemical engineering design and production
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In chemical engineering design and production, there is a distinction between high, medium, and low pressures. I often consult various materials on this topic, and high, medium, and low pressures are mentioned frequently; however, I still don’t have a clear idea of the boundaries between them. What exactly are these boundaries? Let’s discuss it together. Results from searches on Baidu (please check whether they are consistent with practical chemical engineering practices): High pressure is roughly 3–5 atmospheres, that is 3–5 Mpa; medium pressure is about 1 atmosphere, or 1 Mpa; low pressure is below 0.5 atmosphere, that is 0.5 Mpa
The classification of steam grades is as follows: Steam with a pressure below 1.27 MPa is low-pressure steam (i.e., 13 kgf/cm2); steam with a pressure between 1.27 MPa and 3.82 MPa (39 kgf/cm2) is medium-pressure steam; and steam with a pressure above 3.82 MPa is high-pressure steam. This post was last edited by znpmg on 2009-3-17 19:34.]
Regarding containers, they are divided into internal-pressure containers and external-pressure containers; external-pressure containers are classified based on vacuum level； For pressure vessels, they are further classified according to pressure levels as follows: low-pressure (code L) vessels with 0.1 MPa ≤ p < 1.6 MPa; medium-pressure (code M) vessels with 1.6 MPa ≤ p < 10.0 MPa; high-pressure (code H) vessels with 10 MPa ≤ p < 100 MPa; and ultra-high-pressure (code U) vessels with p ≥ 100 MPa.
Based on the steam pressure generated by the boiler, they are classified into low-pressure boilers (P≤2.5Mpa, T≤400℃), medium-pressure boilers (2.5Mpa＜P≤6Mpa, 400℃＜T≤450℃), high-pressure boilers (6Mpa＜P≤14Mpa, 460℃＜T≤540℃), ultra-high-pressure boilers (14Mpa＜P≤17Mpa, 540℃＜T≤570℃), sub-critical pressure boilers (P≤17–18Mpa, 540℃＜T≤570℃), and super-critical pressure boilers (18–22MPA). In short, the criteria for classifying different types of boilers based on pressure vary. In a project, it is also possible to set boundaries according to one’s own needs; as long as they are clearly defined, it becomes easier to distinguish between them and use them. This post was last edited by znpmg on 2009-3-17 19:42]