[knives]

We are challenging a client specification restricting the use of dummy support for piping system operating below the max.ambient temp (i.e. 30 degC). Apparently, its because of strict requirement for corrosion prevention where condensation may occur on these lines. For insulated line, we have suggested to include a portion of the dummy pipe to the insulation (about 3 x insulation thickness) and provide end cover on the dummy pipe in addition to the drain hole along the dummy. Client accepted.

Question now is for non-insulated lines. To avoid direct contact of dummy to elbow, we are thinking of three options:

1) provide additional pad on elbow where dummy can be welded.
2) Replace the dummy with a shaped steel.
3) Offset the support to pipe run instead of elbow where normal pad plate can be welded + dummy pipe support.

Which do you think would be more cost-effective / practical way of doing it?

Discussion

[James Pennock]

There is a 4th option:
Consider the horizontal portion of the line as a Header. Instead of an elbow to the vertical run install a TEE. Extend the horizontal run past the TEE to the next support and then Cap it off as the end of the line. Better yet, add a Flange on the end of the pipe plus a Blind Flange thus allowing for “a future connection”.

[knives]

Thanks Mr. Jop for the suggestion. However, would that extra section of pipe extended to the supporting point be considered a dead leg?

[James Pennock]

I do not know what your commodity is or what type of plant you are working on so I am giving advice at some risk. The only places I know of where a “Dead Leg” are a real “No-No” is on a Pharmaceutical plant or where the commodity is a slurry.
So:
– is your commodity a Slurry?
– is your project a Pharmaceutical Plant

Yes some might consider it a “Dead Leg”. However I am trying to solve your problem and I prefer to consider it an ” inactive future connection” and a legitimate alternative manner of providing a pipe support.

[Bellows Manufacturing]

It is a tricky one to solve off an elbow, but the first question is, it it really of concern? i.e. what is your operating temperature? Is the small heat loss, (or small amount condensation) versus the cost (both engineering and fabrication) worth the time and money?

Conor

http://www.bellowsmfg.com

[Author]

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