Why is there such a big difference in the thickness calculated for internal pressure versus external pressure?
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This post was last edited by turner555 on 2009-8-2 21:12. For 2.21 MPa, DN1500, t=137, with φ set at 0.85, the calculated thickness using GB150’s formulas for pressure vessels is 14.4; yet when using SW6 for external pressure calculations, the thickness comes out to 33.8? Is this normal? What is the typical jacket pressure for jacketed vessels? The specified design pressure is 1.9 MPa, while the test pressure is 2.21 MPa. Does anyone know if jackets that can handle such high pressures exist? I think the jacket is usually filled with hot oil or a refrigerant, and its inlet and outlet should be connected for flow; could the pressure really be that high?
When using the GB150 formula for pressure vessels under internal pressure, the calculated thickness is 14.4; yet when using SW6 for calculations related to external pressure, the thickness reaches 33.8? It’s impossible; you must have made a mistake ； It can’t be that different.
What’s impossible about that? With high pressure and a large calculated length under external pressure, the required thickness must be substantial. In many cases, the wall thickness is determined by the external pressure. When substituting materials, principles must be followed; it’s not sufficient to just choose ones with similar grades. A pressure vessel is essentially designed for fluid flow in and out, right? So there is still pressure present.
1. I think it is feasible to use 0Cr17Ni12Mo2 in place of material 0Cr18Ni12Mo2Ti； 2. Ways can be found to reduce the thickness of the external pressure wall ； a. Add reinforcing rings to reduce the calculated length under external pressure ； b. Add guide plates to reduce the calculated length for external pressure ； C. Replace it with a semi-tube jacket or another type of jacket. For reference only
If it is changed to a half-tube jacket, which standard should be followed for calculating the external pressure? There is no calculation program for half-tube jackets in SW6
It’s possible. External pressure calculates bending stress, while internal pressure calculates tensile stress. If the wall thickness calculated based on external pressure is too large, reinforcing rings can be added to transform the oblong cylinder into a short cylinder, thereby reducing the wall thickness.
The thickness calculated based on external pressure will certainly be much larger. But is the pressure in the jacket that high? If the medium is heat transfer oil, it’s usually at atmospheric pressure; even if there is pressure, it’s generally kept around 0.6 MPa. If the pressure really were that high, then it would be necessary to consider changing the structure.
Reply to turner555: The half-pipe can comply with ASME or HG/T20569-94
What is the name of the standard HG/T20569-94? I couldn’t find this standard online
HG/T20569-94 \"Mechanical Stirring Equipment\" is available online; I downloaded it from there.
This post was last edited by ccr5 on 2009-8-3 18:18. The minimum thickness of a cylindrical vessel under external pressure should be 3 times the maximum operating pressure, while the minimum thickness of a spherical vessel under external pressure should be 4 times the maximum operating pressure