PVELite error on reactor design 2

[massad]

I am working on a reactor design using PVElite with a material of SA387 Gr22 Cl 2. The design conditions are 350psig@1000F and FV@100F. When i put support lugs on this reactor (the mateial is also SA387 ... and bolts of SA325) , I encounter following error.

"Maximum temperature exceeds when computing compressive allowable".

I have also tried the same design with leg support and having same error.

Can anyone suggest that what could be the cause of this error. When i delete the supports i donot recieve this error.

Thanks
Regards
Assad

 

[carthago]

.. I was working on a PVelite version 2005 ..where there was an error on allowable stress of SA 537 cl2

Conclusion : I had to use hand calculations with Mathcad
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.. Please check your allowable stresses ..they are much higher than the the ones for SA- 516 GR. 70
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Further for the sa-537 cl2 , the allowable stress are thickness dependant (I believe they are three thickness ranges)
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question = how to create a new material within PVelite ..(I mean starting from an existing material ) and correcting the allowables..

 

[TomBarsh]

Refer to Section II Part D. This material (SA-384 gr 22 cl 2) is listed on page 34 line 38 (Table 1A). The maximum temperature for Section VIII Div 1 use is 1200° F; the external pressure chart is CS-3.

Putting supports on the vessel appears to force the software to consider longitudinal stress. Per UG-23(b) the allowable longitudinal compressive stress is determined by using the external pressure charts of Section II Part D.

Now refer to Figure CS-3. It states that for temperatures above 300° F Figure CS-2 should be used instead. The curves in Figure CS-2 extend only to 900° F as maximum temperature.

UG-20(c) states "design temperatures for vessels under external pressure shall not exceed the maximum temperatures given on the external pressure charts." Thus for external pressure the maximum temperature is only 900° F in lieu of the maximum temperature of 1200° from Table 1A. Because the allowable longitudinal compressive stress is based on the same method the same maximum temperature has been applied. Thus the software is correct in this case.

The Code does not currently state that the maximum temperature limit for longitudinal compression is limited to that given in the vacuum charts. The "Guidebook for the design of ASME Section VIII pressure vessels" (ASME Press) by Farr and Jawad describes a method to determine an allowable longitudinal compressive stress for when the temperature exceeds the maximum available in the vacuum charts.