Vacuum piping analysis in START-PROF is analyzed according to GOST 32388-2013 code.
To set the vacuum we must specify the negative operating pressure, the difference between internal absolute pressure and atmospheric pressure. If internal absolute pressure is zero (absolute vacuum), then operating pressure should be -0.1 MPa.
Features of vacuum piping:
- Pipes is shortening under external pressure instead of elongating
- Unbalanced axial expansion joints is
shorten under external pressure instead of elongating
- The pipe wall buckling (stability loss) may happen under external pressure. After START-PROF analysis done the pipe wall buckling check table must be analyzed. Also the additional check analysis could be done in Start-Elements.
If the buckling analysis is failed the wall thickness should increased or stiffening rings must be added. The shape and distance between rings should be checked by analysis.
Buckling check of high-temperature piping is not possible because the method of analysis don’t consider the creep effect. See 14.1.1 GOST 32388-2013: This code applies to piping operating under vacuum or external pressure, without metal creep. Wall temperature should not exceed 380 °С for carbon steel, 420 °С for low alloy steel, and 525 °С for austenitic steel.
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Alex Matveev is one of the authors of pipe stress analysis codes GOST 32388-2013 Process Piping, and GOST 55596-2013 District Heating Networks. He is also one of the developers of PASS/Start-Prof software, which is developed since 1965 and used in 95% of process, power, district heating, gas and oil transportation design companies in Russia and CIS countries; it is a standard de facto in that region