Help needed! Under what circumstances can the specified negative deviation for the steel plate in the head of SW6 be set to 0?
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As the title indicates, this device is a horizontal type, and the medium stored in it is water. The materials used for the main body shell and the head are both Q345R steel plates. In the stress calculation document for process equipment provided by the design institute, I found that the negative deviation C1 for the internal pressure cylinder is 0.3, while the specified negative deviation for both the left and right end caps is C1=0. I would like to ask now: 1. Why is the specified negative deviation for the cylinder body 0.3, while that for the left and right end caps is 0? 2. Under what circumstances can the specified negative deviation for the steel plates in the head be set to 0?
The processing thinning amount of the head may have been taken into consideration
What is the processing thinning amount? Could the expert elaborate on this?
See Appendix J of GB/T25198-2010
Take a look at the calculation sheet; the nominal thickness of the head should be the thickness after forming and thinning, right?
The new standard requires that there can be no value of 0 for negative deviation, unless the material provides a positive deviation!
In the calculation sheet, the nominal thickness is used for the cylinder, while the minimum thickness required after forming is used for the head; since it is already in its formed state, there can be no talk of deviations
That’s right. So what is the meaning of setting the negative deviation to 0?
If not set to zero, the software will use 0.3 as the value
Bro, there’s another question: does that mean that as long as the end cap is DN6000 or below, in the SW6 calculations it’s possible to check the option \"specified negative deviation = 0\" for that end cap?