Gasket_Flange Joint 2

[Abhijeet242]

While Flange joint in piping connection, it is very common practice to use Gasket to seal faces. I wanted to know why cant we use confined gasket between faces like making a groove on the face of one of flange and just keeping the face of the other flange flat. This will also reduce the thickness of the flange as there will be no additional gasket seating stress and thickness will only depend on sealing pressure.
Does anybody has any experience in this?

 

[saplanti]

Yes, it can be done within the rules of ASME metal-to-metal contact face flange connections. However, this application may use rubber o-ring seal, hidden in the groove, which will not require gasket seating force.

For this flange connection the gasket material should be suitable with the fluid, temperature and pressure at the joint. Pressurised water pipeline flange connections can be done this way with reduced flange thickness with rubber o-ring.

 

[Abhijeet242]

Thank you @saplanti for the reply. In addition, i wish to know, why this is not common practise to use grooved joint with o-ring or confined gasket? Which one is more advantageous? In my opinion, grooved o-ring of confined gasket should yield technical advantage over regular flange joint with gasket clamped between the faces.

 

[saplanti]

It is common in the water industry, penstoocks etc. The flanges are not shelf product, needs to be manuufacture for the project. AWWA C 207 standard is for these flanges. Some water companies and hydropower companies have their own standards for dimensioning and manufacture.

But these flanges cannot be used for for all industries due to the restriction to use rubber o-rings.

I trust this is sufficient.

 

[MJCronin]

Let's not forget that, for larger diameter piping systems, we assembling something that is not precise....like a watch.

Flanged piping joints are places where small misalignments are resolved...

When a flanged piping system allows usage of a a spiral wound or flat-face gaskets, the slight spool misalignments that commonly occur are not significant and the joints can be made tight.

There must be a much more precise fabrication of a larger diameter piping system using grooved o-rings at the flanged faces.

Is an o-ringed system economical, practical or even necessary for most industrial piping systems ?....... I do not think so

What is the "technical advantage" for an o-ringed system that you claim ? .... You do not explain ...

MJCronin
Sr. Process Engineer

 

[LittleInch]

abhijeet,

A drawing or sketch would be very useful here.

when you say "groove" do you mean an indentaion in one flange or an upstand?

What would you put in the groove?

I don't think your flange thickness is going to change.

People already make "compact" flanges and O ring flanges.

But then as noted above your faces need to be exactly parallel.

Are you trying to metal to metal to metal seals?
What sizes, pressures, fluids?

There's a good reason why gaskets get used a lot - they are cheap and work.

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

 

[Abhijeet242]

Thank you very much for all the answers LittleInch and MJCronin. Few things in the discussion above clarified a lot of things for me. Very correctly pointed out that,the flanged piping joints are the places where small misalignments are resolved. The O-ring system will surely be impractical for long run and/or large diameter pipes. Also the compatibility of O-ring material will be a question. Where these two things,Precision and perfect alignement are paramount, there the use of O-ring will be justified. And this discussion made me realize, perhaps the use of O-ring for sealing has emerged out of the fact that, where during the assembly of two parts we require exact dimension to be maintained and we do not want the assembly to leak. Had there been a use of Gasket at such place, it would not guarantee the exact dimension after assembly.

 

[saplanti]

In this type flange connection one flange has the groove and o-ring the other flange is flat. O-ring is cut for the exact length for the required diameter and bonded for the large flanges.

I do not see the difficulties that you are trying to imply.

The material compatibility, presure, temperature needs to be considered for the flowing fluid and application. This is obvious. That is why o-rings are not in use in all industrial applications.

 

[goutam_freelance]

Ring Type Joints (RTJ) flanges with metallic (mostly steel ring) gaskets are in common use in smaller captive power plant industry. I have experienced up to 50-100 bar pressures. Advantage is quick coupling and decoupling compared to welded joints.