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Flange to Flange joint
6

Flange to Flange joint

Flange to Flange joint

(OP)
Good morning, I have a situation where I have existing 6" std wall piping with a 6" 300# flange WN. The new compressor that came in has a 6" 900# flange. I do not have any room for a spool piece (Flange to pipe to flange). I've looked through B31.3 and interpretations and I don't see anything referencing this configuration. It is a single bevel joint design which makes me think it is OK. The piece will be pressure tested as well. Trying to avoid cutting the flange off my existing piping and re-hydro testing the entire piping.

My question is weather or not I can weld a 6" 300# RFWN Flange to a 6" 900# RFWN Flange to make my connection?

Jmann69

RE: Flange to Flange joint

My immediate answer is no, you have got to be joking.

But just for interest sake - How exactly though are you thinking of doing this??

The OD of the flanges is different (320 mm to 380)

SO I don't know where your "single bevel joint design" is??

A drawing / sketch photo always helps.

But just cut off your class 300 flange and weld on a class 900 instead.

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

RE: Flange to Flange joint

FYI LittleInch is one of the most respected members on this site...

RE: Flange to Flange joint

Your past posts said you were a quality manager at an ASME VIII shop.

And yet you want to weld two flanges together??
Just to avoid chopping one flange off and welding on another??

I think I've answered enough questions on this site to be able to give a smart ass comment or two....

But if you don't want my input I'll just watch from the sidelines.

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

RE: Flange to Flange joint

You want to weld a #300 Flange to a #900 Flange face-to-face?

What??

Post a sketch please.

RE: Flange to Flange joint

I hope he's asking if he can weld two flanges together at the joint (Class 600 and 900 faces opposed 180 degrees). But agreed, just remove the unnecessary flange if it's not needed due to the service.

RE: Flange to Flange joint

I hope it is that, too.

But anyway, welding a flange to the other would still require him to hydrotest the joint IMO.

RE: Flange to Flange joint

Jman69,
You wrote the following: I have a situation where I have existing 6" std wall piping with a 6" 300# flange WN. The new compressor that came in has a 6" 900# flange.
The solution is very simple:
1. You need to cut off your existing 6" Class 300 Flange.
2. Then you need to purchase a new 6" Class 900 flange and weld it to your existing piping
3. Bolt a spare 6" Class 900 Blind Flange to the face of the new 6" Class 900 WN Flange
4. Hydrotest the new weld
5. If the Hydrotest was a success then attach the new Compressor

It should be very simple,
Good Luck

Sometimes its possible to do all the right things and still get bad results

RE: Flange to Flange joint

Jman69,

It is not at all clear what you are proposing to do. Reread your original post. If you ask a poorly worded question with inadequate details, you are going to get some snarky responses. That is on you.

Johnny Pellin

RE: Flange to Flange joint

Agree 100% with the responses.

" It is not at all clear what you are proposing to do. Reread your original post. If you ask a poorly worded question with inadequate details, you are going to get some snarky responses. That is on you."

" It is a single bevel joint design which makes me think it is OK"

How many weldneck flanges come with a square end ???
Are you going to machine the bevel off 1 x flange so you then have a single bevel weld joint ???

RE: Flange to Flange joint

Ok. I read this as welding one flange to another face to face.

Do you really mean end to end I.e fitting to fitting?

That is perfectly ok if a little odd and you may need to check bolt lengths to ensure they don't clash.

A drawing/ sketch would have solved all this.

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

RE: Flange to Flange joint

^^^ What they said... pipe

"The only limits in life are those which we impose upon ourselves."

RE: Flange to Flange joint

To be clear, welding one butt-welding weld-neck flange to another butt welding weld-neck flange of the same bore and pipe size, irrespective of flange class, is acceptable. No piping pup piece is required between them.

RE: Flange to Flange joint

The name's Don, not Einstein, but don't we use flanged connections so we can take them apart? Welding 2 flanges together defeats that notion until the weld breaks. If you don't want to replace one of the flanges and you don't need to disconnect them, why not remove both and butt weld the pipe together?

RE: Flange to Flange joint

We're not quite sure what the OP was asking actually. Welding flange faces one to another is completely idiotic. But welding the butt-welding ends of weld neck flanges to one another is totally fine to make a flanged transition spool from one class to another, as long as the pipe sizes and bores are the same.

RE: Flange to Flange joint

I think the terminology missing in this thread is "back-to-back flanges".

RE: Flange to Flange joint

Typical of so many threads - the OP asks a question but leaves open a critical item (in this case, the flanges orientations), 10 days goes by, several fine engineers attempt to help him, the OP never chimes in, stars are awarded somehow and we are all left hanging. The OP really owes you fine people clarification and a response.

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