Standard for 3-R Elbows

[MTPipeliner]

Anybody know which standard Grade B 3-R elbows are manufactured to? I would think it should be ASME B16.9, but I can't find a reference to them anywhere in that code.

Thanks, Pat

 

[StressGuy]

I must confess, I'm not familiar with what Grade B 3-R means in this context. Do you have a source for that designation? It sounds more like a material specification.

As far as eblows go, I'm only familair with the 1D (short radius) and 1.5D (long radius) elbows as provided for by B16.9. Longer radius "fittings" are usually made by bending straight pipe to the required radius.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[MTPipeliner]

These fittings are an extra long elbow to allow for pigs to pass more easily. The radius of the curve is 3 times the diameter of the pipe. Instead of the more common 1 (Short radius) or 1.5 (Long Radius). The standard for the higher yield fitting are covered in MSS SP 75, but I don't see that Grade B is covered there.

 

[NozzleTwister]

Patrick,

I can only GUESS that your Grade B is defining the material to be equivalent to A106 Grade B which has a lower yeild than the minimum grade shown in MSS-SP-75 and they want the fitting to otherwise be in accordance with MSS-SP-75.

You need to go to your source and get this verified and specify it so there is no confusion.

Also, what grade of pipe is used with these fittings? They should be the same or similar grade. If they differ, verify that the lesser grade has an adequate wall thickness to handle the design conditions.

Good luck,

NozzleTwister
Houston, Texas

 

[1969grad]

3R and greater elbows are pipe bends.

ASME and the Pipe Fabrication Institue have specs for pipe bends.

If there is ever a chance that you will run a smart pig through the bend then use 5R bends.