Flange in which gasket will not be in contact with the process fluid 2

[fergambo]

Hi to all!

First of all, previously to this my first pot, I promise I've tried to look for any thread about this, but really I've not found (may be I've not used a 'key word' to look for...)

Due to the final product specification, we need a flange scheme in which gasket will not be in contact with the process fluid, in order to avoid contamination

We've found the attached scheme, conceptually is valid but it's terrible, so we wonder if there's another option...

Thanks and regards!

Fernando

 

[LittleInch]

Tongue and groove flanges - see ASME B 16.5 would allow O rings or alternative material for your gasket

Or try a Norsok style compact flange - the primary seal is actually the inner heel with the gasket ring for secondary sealing. t#he flange faces are slightly convex and are flattened as part of the tightening.

See

https://blog.miragemachines.com/topic/compact-flanges

and scroll down a bit.

There will always be some contact with the fluid but can't see why you can't just get a suitable gasket material? or use RTJ rings of a suitable material??

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

 

[robyengIT]

1 - is it not possible to make a conical coupling like for water plumbing at home ? (

http://www.intertubi.com/prodotto-it/GIUNTO-TRE-PEZZI-giu3p-113.html)

2 - as LittleInch said, you must avoid any contact with any material but steel (even the lead or tin gasket) ?

 

[fergambo]

Thanks for the info, we'll study these options.

Suitable material may be a problem, for example EPDM was suitable, but it seems EPDM contains a 'mineral load' (probably to improve properties) not mentioned in the technical sheet (as inconsequential in 99.9% of the applications) that contaminates the process due a extremely low conductivity is requiered.

 

[EdStainless]

There are seal materials available that have been tested for use in ultrahigh purity applications.
You need a better seal supplier.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Compositepro]

What you ask is simply not possible. The gasket is the fluid tight seal and therefore, by definition, must be in contact with the fluid. You could possibly use a barrier fluid purge to avoid contact. Crevices are usually undesirable in high purity applications.

The example you propose does not prevent contact. It merely creates a long narrow crevice filled with fluid between the gasket and the main flow channel. The same effect is created by an O-ring face seal where the faces have metal-to-metal contact. You can do this by replacing the gasket with a metal ring with O-ring grooves on both sides. Or use a metal-to metal seal.

There are many high purity applications with seals that work.

 

[fergambo]

Ok about the gasket by definition must be in contact with the fluid, but is quite different if the flow impacts the gasket or not and if there's a 'physical barrier' to avoid the gasket particles to be washed down by the flow.

Due to is an existing Plant and flanges afected are about 70, the cost impact is high; for example the attached is a Coperion standard, very expensive itself and implies to change (cut/weld) all (the now ASME 150#) flanges.

Probably a ferritic base metal-metal seal by means of a metalic gasket would be a good option, as in this process the metallic particles from pipe can be removed by means of a neodimiun magnets.

Thanks to all for the help.

 

[moltenmetal]

Your choices are to a) use a gasketless design, which is used in things like small threaded pipe unions and tube fittings b) use a gasket which is made of the same material as your flanges, i.e. a "lens ring" or ring-type joint flange or c) give up. All gaskets are, by definition, wetted to some degree by the process fluid, and must be so to work at all.

 

[btrueblood]

Use a teflon (PTFE) coated gasket or encapsulated o-ring. Or, as Ed suggests, find a manufacturer of EPDM gaskets that make a low-extractable version (look for NSF 51 and 61 ratings for starters).

 

[quadtracker]

Taper-lok pipe flanges use a seal ring which is the same material as the flange. There is a male and female flange that mate together with a metal seal ring between them. Exceeds ASME code section VIII. Size range from 1/2" to 83" up to 40,000 psi. Temperatures from -350 to 1600 F . link :

http://www.TAPER-LOK.COM