The issue of allowable stress for 12Cr1MoVG steel pipes
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I encountered a really annoying issue: for steel pipes made of the 12Cr1MoVG material, at 350 degrees Celsius, the yield strength is 167 MPa (according to GB150-2011). The allowable stress is therefore 167/1.5 = 111 MPa. However, the standards for thermal power plant pipelines specify 143 MPa. Why is that? There’s clearly something wrong here; in standards such as DL/T 5366-2006, DL/T 5366-2014, and GB/T 32270-2015, the value for 350 degrees is 143 MPa
Thermal power plants use the 5310 standard
Why is the difference so large? Thank you!
5310 is merely a material standard; the allowable stress is not specified in 5310
Pressure vessels are also subject to the 5310 standard
Different standards result in different safety factors; for the same material, the allowable stress varies.
This post was last edited by FMSD on 2016-9-27 at 16:38. The allowable stress in the power industry = MIN(tensile strength/3, yield strength/1.5); the allowable stress in the pressure vessel industry = MIN(tensile strength/2.7, yield strength/1.5); the allowable stress for welded steel vessels under normal pressure = MIN(tensile strength/2.4, yield strength/1.5). In high-temperature operating environments, the allowable stress is generally determined by the yield strength. Based on these principles, even at room temperature, the allowable stress in the power industry cannot be higher than that in pressure vessels.