PN40 Rated Loose flange & stub end connection

[TEIGRAY]

Hi all,

I'm designing a prototype that is machined from bar with a stub end connection, the idea being that a loose plate would slip over the prototype body and form a lap joint connection. The reasons for this is that we would require the loose flange to be rotated for accurate bolt hole mating, and would like to avoid any welds between the stub end and the lapped flange to allow for disassembly should this be required.

The ASME standards allow for a stub end + Lapped Flange for Pressure ratings ASME #150-#600 and beyond. However EN 1092-1 only allows for a Loose plate & Lapped pipe end (Type 02 & Type 33) up to PN16 Pressure rating.

I require this kind of connection for PN40 pressure rating.

My question is that the other apparent connections of this type are

- The same loose plate flange& a weldring neck (Type 02 & 35)
- Loose plate flange & a weld-neck collar (Type 04 & 34)

Both can be used at a pressure rating of PN40.

Do these two combinations require welding between the stub ends (Weldring Neck (35), Weld-neck collar) and the loose plate flange itself one the bolt holes are aligned?
As in, can the two be disassembled from each other once they are fully fitted? (assuming the loose place can slide off the pipework no problem).

I've read through EN 1092-1 and cannot find any confirmation on the correct assembly methods of these combinations so some clarification would be amazing!

 

[Gator]

"Can the two be disassembled from each other once they are fully fitted?"

Yes. That's one of the purposes for this type of flange.

 

[rconner]

There are several past threads discussing such structures e.g.

http://www.eng-tips.com/viewthread.cfm?qid=266009.

 

[LittleInch]

Do they require welding between the stub ends and the loose plate flange. NO.

Can they be disassembled. YES.

I have never heard of a stub flange and loose flange ever being welded together, not even tacked.

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

 

[TEIGRAY]

OK Perfect!

Why does the Lapped pipe end only appear to be up to PN16 pressure rating?
To get a PN40 rating I would need to go for the Weldring or Weld neck collar instead it appears,
Not sure I understand why from the dimensions but there you go

 

[europipe]

Why does the Lapped pipe end only appear to be up to PN16 pressure rating?
Because the stub from plate material is not as solid as a forged fitting.

 

[moltenmetal]

In ASME B16.5 and the ASME B31.3 piping code, there is no limitation on the use of lap joint flange construction. Lap joint flanges may be used to 2500# class. This construction may also be used as body or nozzle flanges on ASME VIII pressure vessels. The requirements and dimensions of the lap joint backing flange and lap joint stub end are both covered in the B16.5 standard.

There may well be European rules which restrict the use of this construction to lower pressure ratings, but if there are, this is the first time I've heard of them.

Europipe's assertion that this limitation has something to do with the use of plate may apply to the European rules which I know nothing about, but does not apply to B16.5 flanges to my knowledge. B16.5 lapjoint backing flanges have a hub, and unless I'm mistaken, you are not permitted to make a hubbed flange from plate- it must be made from a forging or a casting. It may be permitted to make a designed Appendix II ASME VIII vessel lap joint backing flange from plate.

There is a different flange construction where the backing flange isn't a solid flange but is rather a 2 pc split collar which is either bolted or welded together after it is installed around the lap joint stub end. That flange construction, which is often seen on solid plastic or glass-lined carbon steel construction, is not an ASME B16.5 flange design but rather a manufacturer-specific design, and therefore may have more limitations in relation to its use.

 

[Gator]

FWIW, stub-ends and plate flanges are (or, were, at one time) sometimes fabricated from plate for low pressure applications in the pulp and paper industry, probably in others as well. I forget the details.

 

[europipe]

I think You have to use type 32 weld-on collar plate for your purpose.

 

[europipe]