ASME Flanges Mating Question

Yes.....

However, you have not mentioned the flange facing style.

Are both flanges "raised face", flat face or what ?... the face style must match !

The flange construction type does not matter....ie. a weld neck flange of the proper size, Class and flange face type wil mate with a similar "slip-on" or Van Stone flange

You must, of course, evaluate both the SCH 80 and the SCH 160 flanges to determine that they are acceptable for the pressures and temperatures you expect to encounter in service.

Also ensure that the bolting materials and flange gasket ratings are accetable for the service.

Thank you, MJCronin. The flanges are both raised face. And to clarify again, my piping system uses SCH 80 and the component that we are getting comes in SCH 160. Therefore, as far as being able to withstand the pressure, it is way oversized for my application.

OP

There are another issues you need to give some consideration to.

This item is the difference in the relative ID's of the two schedules.

1 1/2" Sch 80 ID = 1.500

1 1/2" Sch 160 ID = 1.338

You should check ASME B31.3 (or whatever your governing piping Code is) for guidelines when there is a difference in the inside diameters of two adjoining elements. You may need to use a short length of Sch 160 pipe next to your "Item" and taper bore one end of the pipe to match the rest of the run.

You did not state what your commodity is

or

which direction (just in or just out) the flow is

or

if the flow is in one side of the Sch 160 item, through and out the other end

or

what the "Component" is

For welding neck flanges, it would be logical to taper (3:1 or more) the inner bore of the S160 flange so that it matches the i.d. of the S80 flange where the two meet.

Is this really acceptable as per code? or just a Lead solution?

For my future reference plss. Thank you

I think it is acceptable, and it ought to be acceptable on the basis of any stress calculations. But it depends on how rationally the governing Code is written.

Since warantee considerations make grinding the ID of the component undesirable, order a sched. 160 weld neck flange, counterbore it to sched. 80, and make the weld to your piping. This really pays off if the component must be serviced or replaced. Off the shelf is good.

I don't think anyone suggested grinding on the component.

May be you don't think suggesting grinding from inside, but actually that is exactly must be done at this case. I faced that case 29 years ago, exactly at 1982, where we need to connect an ASME flange RTJ, NPS 20, Sch. 120 into a pipe with the same NPS, but with a different Sch. 100. The unique solution was to make a taper for the flange from inside, because you can't make that taper from outside, since the OD of both flange and pipe are the same, check all dimensions as per ASME B36.10M.

The same scenario can carried out when you need to weld two pipes with the same NPS, but with differ schedules, where you have to make a taper to the thicker pipe wall thickness.

See this sketch for joint design for connecting two pipes with unequal wall thicknesses: Joint_Design_for_Pipes_of_Uneqal Thickness.

Indeed! But now we are speaking of grinding (or machining) on the flange, not on the custom component.

Yes, actually I mean and I speak about grinding (or machining) on the RTJ flange from inside of its neck. The story was happened at 1982 to a RTJ flange, where we tapered its neck from inside diameter to match its thickness with the thickness of pipe intended to be welded, taking into consideration that the min. taper ratio shall be 1:3 as per ASME code.

Note. Also, it is acceptable per code to make that taper to any piping component or fitting (elbow, tee, reducer, ... etc.) to match the welded thicknesses.