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#76343 - 03/24/22 11:18 PM Intake duct analysis
pradeepalb1143 Offline

Registered: 10/26/21
Posts: 7
Loc: India
hi, can any one help me out from this
I am working on intake and exhaust duct analysis of DG, and i need to analyze for negative pressure so in Caesar is it possible to analyze for negative pressure? i am using Caesar version 12
In the past conversation related to this type of comment it is observed that buckling is not able to do in Caesar, so if not possible in Caesar then which tool is preferable for negative pressure piping analysis

observation: I have tried for the same pressure with positive and negative values in Caesar and i got minor change in support load and same in the stress result


#76344 - 03/25/22 08:41 AM Re: Intake duct analysis [Re: pradeepalb1143]
Richard Ay Offline

Registered: 12/13/99
Posts: 6164
Loc: Houston, Texas, USA
You cannot analyze with a negative pressure in CAESAR II. If you do input a negative pressure, you may see an effect on loads if the model includes expansion joints or the Bourdon Pressure effect is activated. However, for stress computations, the absolute value of the pressure is used. This is so that in equations such as [stress = PD/4t + iM/Z], a negative pressure does not reduce the stress.
Richard Ay - Consultant

#76345 - 03/25/22 06:06 PM Re: Intake duct analysis [Re: Richard Ay]
Borzki Offline

Registered: 09/16/04
Posts: 710
Loc: Traz
You can check buckling for negative pressure. There are procedure in ASME to perform it. You may need to add stiffener ring in lieu of increasing the thickness as required.

Warm Regards,

#76346 - 03/27/22 02:16 PM Re: Intake duct analysis [Re: pradeepalb1143]
danb Offline

Registered: 04/22/05
Posts: 1426
Loc: ...
ASME VIII, Division 1, UG-28, UG-29, and UG-30 are applicable.

#76347 - 03/29/22 07:18 AM Re: Intake duct analysis [Re: pradeepalb1143]
pradeepalb1143 Offline

Registered: 10/26/21
Posts: 7
Loc: India
Thanks for all your valuable response,

As per the suggestion taken above, I discussed with client and they are asking Air duct analysis as per ASME AG-1. if any one is aware of this code please share your thought related to the stress analysis.

I have ASME AG-1_2009 document but in that SECTION GA is preferred for PRESSURE VESSELS, PIPING, HEAT EXCHANGERS, AND VALVES and this Section GA is not available from outsource please suggest me if any one did the similar duct analysis



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