Pipe flanges

[michael mParticipant @michaelm]

A question relating to full size practice rather than models. Could someone please explain why some pipe flanges have grooves in the face whereas others are quite smooth. I'm not talking about an O-ring groove but in the case where the flanges are sealed by flat sheet PTFE gaskets.

With Thanks, Michael.

[michael mParticipant @michaelm]

[Neil WyattModerator @neilwyatt]

I don't know about flanges, but I have read that a simple shaft-in-tube bearing can use a series of grooves to reduce leakage. Allegedly you get a series of steps in pressure between the oil reservoirs in each groove that lead to a much slower flow than a plain shaft, similar to but not identical to the situation with a labyrinth seal..

I'm not sure if I believe this or not, but if it's true then it would also apply to pipe flanges.

Neil

[Mark Simpson 1Participant @marksimpson1]

I know a little of what is common practice in process piping, though there are many types of flanges the basic hierarchy is as follows; gasket materials vary widely according to industry, fluid and temperature….

Flat faced: the lowest pressure, cheapest and most common (150 – 300 psi), uses common gaskets

Raised Face: the flat area is reduced to within the bolt P.C.D to increase the pressure on a smaller area of flange most common to 600psi, uses common gaskets

Ring Jointed:there is a groove in both flanges to take a metal ring as a gasket pressures beyond 600 psi to mega

Tongue and groove: often used to ensure piping is assembled the right way around (and lots of other reasons)

Quite a nice description here http://www.wermac.org/flanges/flanges_raised-face_flat-face_ring-type-joint.html

There are lot's of variation, especially from industry to industry, but I think the above is a fair simplification: we shall see

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Michael, flanges that are smooth are designed to fit together metal to metal with no gasket, although one may use a jointing compound e.g. Wellseal. The flanges that have the grooves that you describe, must have a gasket between the faces, the gasket material being applicable to the substance flowing in the pipeline, the grooves make an indentation in the gasket and make for a better seal. Some info on flange types:- **LINK**

Regards Nick.

Edited By Nicholas Farr on 04/09/2014 23:04:29

[Boiler BriParticipant @boilerbri]

I have never heard of a flat face flange being put together without a gasket, or managed to make one seal without some form of gasket material or compound (boss white or stag) on the gasket faces!

The ones with grooves are hellish to clean up after they have been sealed for a year or two, with steam passing through them.

There are 'tables' for flange sizes and specifications.

http://www.hattersley.com/documents/13a.pdf

Bri

[michael mParticipant @michaelm]

Many thanks to Neil, Mark, Nick and Bri for your comments and links. I think that possibly Nick has best answered my question for the particular application concerned, i.e carrying a corrosive liquid at some 10 bar pressure. The integrity of the seal is obviously paramount. On my original post I forgot to attach a picture but have done so here should it be of interest. And no, I didn't make the flange.

Thanks again

Michael

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