Dear Sir,

My client has raised a requirement for Pressure equivalent flange leakage test in dynamic SMS case. I had prepared an excel sheet to convert the force and moment into equivalent pressure using ASME SEC VIII Div.1.


P force equivalent = ((4*Axial Force)/(3.141*G*G))
P Moment Equivalent = ((16*SRSS of Moment longitudnal,circumfrential)/(3.141*G*G*G))

Pequivalent = P force equivalent + P Moment Equivalent

Ptotal = P + Pequivalent

This is the same method how caesar calculates equivalent pressure i assume. But this method is independent of any stress calculation along the hub length or flange and use of any multiplier for allowable pressure.

The other method directs use of a multipiler 1.0 for sustain case and 1.5 for operating case and calculate 3 terms i.e
1. Longitudnal stress in hub.
2. Radial stress in Flange.
3. Tangential stress in Flange.

Do caeasr use any such techniques in using Pressure Equivalent method?
Or do i need to use any multiplier for allowable pressure?
Is there any code guidelines for flange leakage in dynamic cases?

Yes this is how CAESAR II computes the value for Ptotal. Your remaining questions deal with the "flange allowables". I believe this article on page 6 will answer your questions.

Dear Richard,

Thankyou for your confirmation. I read the coade newsletter. but still I am puzzled about the allowables for dynamic case.

With refrence to Exhibit 2 on page 8 of newsletter it seems that Pressure equivalent method uses two allowables. But caesar module for Peq uses only the first one i.e (Pfd does not exceed the ANSI B16.5 flange rating.)

Can i use the same allowable (i.e 1*Allowable pressure at that temperature) for my dynamic SMS loads on flanges?

No, Exhibit 2 says that when you determine Peq, it must be less than the B16.5 flange rating. Furthermore, the computed stresses must be less than the appropriate allowable stress.

Without any additional guidance from the Codes, I (personally) would use the same allowable values.

A multiplier of 1.5 for rated table pressure can be used for Pressure equivalent method, but only for exceptional operating conditions like extreme wind or seismic conditions as defined in CODETI 2005 ( French code)

Refer to the article CODETI "C 2.2.8.2"

Refer the attached file for your refrence