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# Mandatory Appendix-2-3 "G" value for O-Ring seal ?

## Mandatory Appendix-2-3 "G" value for O-Ring seal ?

(OP)
When designing a flange with an O-Ring seal, which is 31" OD x 30.45" ID with a 0.275" C/S, should the "G" value be determined as stated in 2-3, or, should the "G" value = the OD of the O-Ring as noted in 2-5(c)(2).

Example:
If using the 2-3 definition of G, and assuming that "N" from table 2-5.2 is equal to the O-Ring cross section, bo =(0.275"/2)=0.1375", which is less than 1/4", so "G" = 30.725 (the mean Ø of the Contact face)

OR,

Should "G" = the Gasket OD = 31"

### RE: Mandatory Appendix-2-3 "G" value for O-Ring seal ?

bayardwv, your reference to 2-5(c)(2) is confusing to me, I don't see the relevance.

I'd calculate G as per 2-3 and Table 2-5.2 (same thing). For your case. G = 30.725.

Maybe a point of interest, maybe not: Appendix Y which assumes essentially self energizing gaskets, defines G as the mean diameter; i.e. no consideration of effective width, b , bo, etc.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

### RE: Mandatory Appendix-2-3 "G" value for O-Ring seal ?

(OP)
I agree, but several other co-workers believe that when using an O-Ring seal "G" is equal to "Go".
Please note my original post incorrectly stated 2-5(c)(2), it should have read, 2-5(c)(3)

To support their belief they reference the information in our PV Elite Software printouts that state that "G" = "Go" (Self Energizing)
and that 2-5(c)(3)(-a) reads..."The required bolt load for the operating conditions Wm1 shall be sufficient to resist the hydrostatic end force H exerted by the maximum allowable working pressure on the area bounded by the outside diameter of the gasket....
In addition it's been pointed out that Appendix 24, figure 24-1 shows "G" as the Outside edge of the O-Ring and not the mean diameter, as is shown for a flat gasket.
Basically I need to know what is the correct way to determine the value for "G" when using an o-ring seal on flange designed in accordance with Appendix 2.

I did sent an email to PV Elite support asking for clarification as to how they determine the value of G for self energizing seals.

### RE: Mandatory Appendix-2-3 "G" value for O-Ring seal ?

bayardwv, OK I had not read that sentence earlier. It would seem to justify use of the OD. As a matter of convenience, and as use of the OD provides a more conservative result than use of "G", I'd go with the software.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

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