Multiple gaskets in a Flange

[Beginner - Inspector]

Greetings

Please advise whether two gaskets can be installed in a flat face flange to arrest leakage in the instrument air line. The flange dimension is 2 inch 150# Flat Face.
Does any engineering practice or reference advise that multiple gaskets can be installed in a Flange joint?

 

[r6155]

This is not a good engineering practice.
Why flat face?
The gasket material is?????
Careful with torque of bolts.

Regards

 

[MJCronin]

Gasket materials also are available in various thicknesses .... Perhaps a thicker (or thinner?) materials would be suitable

MJCronin
Sr. Process Engineer

 

[LittleInch]

Doesn't sound like a good idea to me.

What gasket material are you using?

EPDM is commonly used for flat face flanges.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jmmiller1206]

I do not recommend double gasketing.

Suggest reviewing the pipe spec.

BUNA-N or expanded PTFE gaskets may be good options if available.

 

[iangineer]

I agree with the other responses that double gaskets is not a good practice. For a leaking flange, check to make sure the flange face doesn't have any gouges or other possible leak paths. Make sure the bolts are properly torqued (bolts stressed enough to properly seat gasket, but not stressed enough to bend the flange). Bolts on a 2" 150# flange with a standard spiral wound gasket shouldn't have a stress more than about 64.4 ksi or it could warp the flange. There are charts for standard bolt torques you can find online that are fairly accurate for black bolts or PTFE coated bolts.

 

[KevinNZ]

I would also ask why class 150 with flat face flanges. If the raised face has been removed then the flange is longer complies with the flange code, Class 150 flanges are are designed to be used at their pressure rating not with full face gaskets. What do these FF flanges have for a gasket face?

 

[SnTMan]

KevinNZ, flanges may indeed be flat faced and may be converted under certain conditions. See B16.5 (2003) 6.3

Regards,

Mike

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

 

[r6155]

See B16.5 (2020) 5.3.5 (b)

(1) low-strength bolting within the limitations of
para. 5.3.4 should be used with ring gaskets extending
to the bolt holes or
(2) bolting of low (para. 5.3.4), intermediate (para.
5.3.3), or high (para. 5.3.2) strength may be used with full
face gaskets extending to the outside diameters of the
flanges

Regards

 

[KevinNZ]

my mistake, I was thinking of the min flange thickness requirement with the raised face. Yes you can have FF flanges as long the t_f is maintained.

I would be concerned with FF flanges applying the required loads to suitable FF gaskets. For example what full face gasket could be used for high temperature service. The OP has as an air application so getting a bit off topic.

B16.5 (2020) 5.3.5 has rules about the gaskets and bolting to cast steel FF flanges. Does refer to using 'soft' 1a gasket materials

 

[r6155]

I have met some pipe installers who believe that FF flanges should have full gaskets extending to the outside diameter of the flange.

Regards

 

[LittleInch]

Well the OP hasn't logged on since asking the question and doesn't reply to most of the posts so guess we'll never know...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

You can always go for three gaskets

https://www.linkedin.com/posts/chri...?utm_source=linkedin_share&utm_medium=ios_app

Huub
- You never get what you expect, you only get what you inspect.

 

[LittleInch]

R6155, what sort of gaskets would you use for a flat face flange?

I can't see anything other than a complete flange gasket for a FF flange myself.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r6155]

@ LittleInch
See Table 1 in AWWA C-207 Steel Pipe Flanges for Waterworks Service.

Regards