Coupling (half) O.D. Tolerance

[AARCUDA]

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,

 

[weldtek]

AA;
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.

 

[AARCUDA]

Thanks,

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.

 

[pennpiper]

AARCUDA,
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

http://www.pennusa.com/pennpage/directory/forgecat/threaded/3thcocps.htm#thhalfcoupling3000

You will see that the lowest rating of Forged Steel Half Coupling listed is Class 3000

 

[AARCUDA]

Pennpiper,
"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.

 

[SnTMan]

AARCUDA, if possible identify whether it is made to any standard or specification which, I would guess, will give manufacturing tolerances.

If not, if it's just a thing you can buy, tolerances may be up to each manufacturer.

Regards,

Mike