Pipeline branching - Maximum Weldolet Size 2

[McDermott1711]

Hi everybody,
In one of the natural gas transportation project, Client does not allow using weldolet larger than 2" for branching. In other words he/she asked for pipe-to-pipe with reinforcing pad (saddle) for larger than 2" branches (header is 42"). What's behind this? Is there any code (or practical) requirement behind this?
Thanks in advance.

 

[pennpiper]

What's behind this?
Ignorance!

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

 

[McDermott1711]

Thanks Pennpiper for your reply.
What's your opinion? For a 42" header, what would be the maximum size for weldolet branch?

 

[BigInch]

Most likely their experience. Mechanical strength, weld quality, corrosion, and fatigue concerns may all contribute to their exclusion of larger diameter weld-o-lets. There are a number of companies that do not allow their use when a branch diameter is greater than 1/4 of mainline size.

 

[pennpiper]

McDermott1711,
Your question "For a 42" header, what would be the maximum size for weld-o-let branch? "
I suggest you contact Bonny Forge (

http://www.bonneyforge.com/products.php?pg=branch&subpg=weldolet)

or WFI and ask them.
If they make it then it should be fit for use.

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

 

[SNORGY]

If a WOL or TOL can't go on a 42" P/L, I'd be curious to see what they do regarding pressure transmitters, manual local blow downs, vents, pig signalling devices...

I suspect they have a specification that calls for branch reinforcement of the full encirclement type or something like that, and it might be ambiguous or silent on the smaller connection types.

 

[LittleInch]

The code you're using will specify what reinforcement is required. Integrally reinforced fitting to give them their generic name (weldolet is a trade name of Bonney forge) should be acceptable.

What I suspect is that at some point someone tried to weld some big weldolets in a large diameter thick header and bent it due to the heat input on one side. A pipe and reinforcement pad can be welded separately so can ease this issue.

This is one reason I don't like some Client specs. They have a bad experience somewhere,change the spec then no one will change it back...

Reducing and equal tees are probably better but you can't always do this.

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

 

[BigInch]

A <= 2" weld-o-lets limit wouldn't present a problem for instrument connections.
Small diameter free to air blowdowns on high pressure gas lines rising up from buried pipelines, can be problematic because of high "jet thrust" loads and fatigue from oscillating load directions due to turbulence from exiting gas streams. IMO those should always be made with reducing tees and reducers where practical. The riser may need additional structural bracing as well.

 

[Krausen]

Little Inch is probably correct on the reasoning here. 4" & larger weldolets require much more heat input into the header pipe vs 2" & smaller. Many contractors/pipeline welders I've run across cringe at 4" weldolets, especially if it's an XS/SCH 80 weldolet designed as a branch for STD wall header pipe with multiple taps. This is the worst case scenario I've run into. To avoid heat warping the header, wall thickness of header should match weld out schedule as a best practice. I've seen multiple pipeline projects where this was not the case.