Elbow Schedule

[safiamoiz]

We need to replace a 6 NPS Sch 120 elbow in piping system. In our store we have a 6 NPS Sch 160 elbow. Can we use this new elbow with a higher sch.

 

[MJCronin]

Sure.... It should be fine for the pressure.

Is it of the same material as the old elbow ?

Make sure that you taper the inside of the elbow near the two welds ( I assume that it is butt welded).

ASME B31.1 states that it should be a minimum of 3:1 taper

 

[rmw]

Same 'tip' as given in the Nuclear forum about the Sch 80 pipe piece.

rmw

 

[safiamoiz]

MJCronin,

The material is same ASTM A-234 WPB. However, as you know both will have different ID at root face. Would it hurts.

 

[Mr168]

As MJCronin suggested, you would need to counterbore and/or taper the the ID of the heavier fitting to provide a 3:1 transition.

If you left it alone and just tried to make the weld with the dissimilar ID's, not only is it poor practice and most likely a code violation, but you also wouldn't meet the high-low/maximum permissible ID mismatch weld fit-up requirements of most ASME codes.

 

[spayette]

two items of possible concern:

1. The thicker ell decreases the flexibility of the piping system which could potentially result in higher stresses and/or higher loads on branches and equipment nozzles.

2. The smaller ID of the ell will increase pressure drop through the system.

In probably most instances neither concern may result in a problem, however, if you are not confident in evaluating these issues yourself then involve someone who can. This would be my recommendation.