Coupling (half) O.D. Tolerance
Coupling (half) O.D. Tolerance
(OP)
Looking for information on the outside diameter dimensions and tolerances for 150 lb half couplings. I currently recieved some 1/2" NPT half couplings from my supplier that had an OD that measured .960". I complained about it but the supplier said it is typical to have large fluctuations in the OD of couplings. I know the nominal OD of a 1/2" NPT half coupling is 1.063". I also use 3000 and 6000 lb couplings, so eventually I am sure this information will come up on these larger fittings as well. Anyone know where I can find this information? Any help is appreciated.
Thanks,
Thanks,





RE: Coupling (half) O.D. Tolerance
I think you want ASME B16.11. I'm not sure if you'll find tolerances for coupling OD's. You may have to work of off wall thickness.
RE: Coupling (half) O.D. Tolerance
I believe B16.11 applies to forged fittings, which in the couplers case is 3000 lb and up. Also, calculating the minimum OD based off of minimum wall thickness can be a little tricky to work with, since the maximum major diameter of an internal NPT thread is not clearly defined. I suppose I could take E1 plus the max thread height (.057) from machinery's hand book and assume that is the maximum major diameter. For a 1/2" NPT thread, that puts the max. major at .836". Now if I could find what the minimum wall thickness of a 150 lb half coupling is, than maybe I can come up with a reasonable number for the minimum OD of said coupling. Thanks for looking.
RE: Coupling (half) O.D. Tolerance
I am confused. You are asking about "150 lb half couplings". This is consistent with Galvanized Cast Iron fittings. Is that really what you are looking for?
If you look at this link
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You will see that the lowest rating of Forged Steel Half Coupling listed is Class 3000
RE: Coupling (half) O.D. Tolerance
"150 lb class" simply defines the pressure rating at a particular temperature of the fitting, depending on the material. 150 lb fittings can be plated/dipped carbon steel (many different grades/alloys), unplated carbon steel, stainless steel(again many different grades/alloys), hastelloy etc. These fittings can be castings, forgings or simply machined from bar. I am trying to find the tolerance on the OD of a 150 lb coupling regardless of material. The coupling I am referring to in this forum is a 1/2" NPT half coupling machined from 316 S.S. bar.
RE: Coupling (half) O.D. Tolerance
If not, if it's just a thing you can buy, tolerances may be up to each manufacturer.
Regards,
Mike