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Wye lateral on pipeline
3

Wye lateral on pipeline

Wye lateral on pipeline

(OP)
Hi all,

I am facing problem of high stress at the wye lateral.
According to B31.3, there is no guidance except pressure rating.

What happens to external load generated by thermal forces.
Should Wye lateral be fixed with the anchor to eliminate external forces.

Thanks

RE: Wye lateral on pipeline

3
External load is generated by attempting to restrain thermal expansion, or contraction.  A freely moving line will develop no, or very little axial stress from thermal loads and, since external loads are generated only by restraining the movement in some manner, only bending moments from end displacements and rotations at elbows and, in your case wyes, are produced.  Bending moments usually produce less stress, as pipe is quite efficient in carrying bending loads in just about any direction until they hit areas where stress concentration factors become important, the same elbows and wyes.

Generally speaking, adding anchors increases stress, so you should look to increasing flexibility to reduce stresses.  The alternative is to add an anchor to block stresses arriving to the problem area from the side with the greatest temperature differential, provided that the same anchor does not decrease the flexibility of the problem area, you may have some success.

If you can add an anchor to a connecting pipe that is trying to move the most relative to the others that pipe would develop high stress, but perhaps the other two segments would be relatively free to move and potential stresses in those lines would reduce.

I would try to increase the flexibility of the pipes connecting to the wyes before adding an anchor.  Don't let long straight pieces connect into the wye, as they will develop high axial forces as each pipe tries to restrain the others and all of that will come together at the wye.  Put a gradual bend to some other misaligning direction in any segment of connecting pipe that you can and run the case again.  You might get lucky, otherwise carefully try introducing an anchor on the line that wants to move the most.  Repeat until you get some success.

 

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us.  Lisa Gansky

RE: Wye lateral on pipeline

Are you talking about a "lateral" (i.e., a branch let into a run at 45°, or a "wye" (i.e., two lines that join at 90° and the exit pipe leaves at 135° to both inlets)?  I've never seen a high pressure or big-inch wye connection, I know they are in the books, but I've never seen one in the wild.  Laterals on the other hand are seen (not terribly common, but seen) in pipelines on occasion.  The pipe stresses on a lateral generally work out to be simliar to a forged tee, and I've never anchored one of them in a buried pipeline.

David

RE: Wye lateral on pipeline

"Y" The crotch angle doesn't have to be 90.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us.  Lisa Gansky

RE: Wye lateral on pipeline

(OP)
Thanks for all your replies.

Most of the wyes are okay as far as flexibility is concerned.

There is one in particular that the branch turned 90° inside a road crossing. The sleeve becomes a virtual anchor.  The distance between the wye and sleeve is about 10 feet.
The is 20" pipe and 200m long.
I want to stop the wye lateral movement using an anchor to prevent bending at the pipe near the sleeve and at the wye lateral.

Option 1. bum up the size of the sleeve.

Option 2. allow the wye to move.
          Add a flexible spool (rubber hose)
          to accommodate the movement.

Option 3. fix the wye + expansion barrel.

 

RE: Wye lateral on pipeline

(OP)
Postzdas04 (Mechanical)     

5 Sep 11 13:50
Are you talking about a "lateral" (i.e., a branch let into a run at 45°, or a "wye" (i.e., two lines that join at 90° and the exit pipe leaves at 135° to both inlets)?  ........... pipeline.

David

Yes, this is custom fabricated wye lateral that the branch off 45° from the inlet and outlet.  This is above ground slurry pipeline for mining project.  Technically speaking, wye lateral should be
design according to B31.11.   

RE: Wye lateral on pipeline

If you are worried about it becoming an anchor, similar to the Alaska Pipeline construction to control thermal expansion and contraction, why don't you install a horizontal "U" with four 90 degree bends?

Mike McCann
MMC Engineering

 

RE: Wye lateral on pipeline

Or a horizintal "Z" with two 45's and two 90's.

Mike McCann
MMC Engineering

 

RE: Wye lateral on pipeline

(OP)
If you are worried about it becoming an anchor, similar to the Alaska Pipeline construction to control thermal expansion and contraction, why don't you install a horizontal "U" with four 90 degree bends?

Thanks, that's a good idea.

However, in a slurry pipeline, there will be too much erosion.

The pipeline corridor is also quite narrow to fit "Z".

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