Are all threaded fittings the same?

ChrisJ

When dealing with iron threaded fittings are they generally all the same dimensions from different manufacturers? And what about older ones?

For example if I take a new Ward 2" ell should it match an older one on a steam system or are there often differences?

Bob Bona_4

Generally Your standard iron pipe and fittings are threaded NPT. There will be slight variationsin tolerances. Especially with overseas stuff. Ward is one of the most predictable.

KC_Jones

Chris are you talking about center to end dimensions or the thread dimensions? The center to end dimension from the center of one pipe to the entrance of the other pipe? So if you take out one 2" ell will a new ell be a direct replacement. In my experience with fitting of all kinds there are definite variations, but they shouldn't be such that you can't swap one for another. Some of the really old stuff might be out of current standards, but standards probably didn't exist when they were made. Of course I have also seen manufacturers having one set of dims in their catalog, a different set of dims on the 3D model from their website and the real world part not matching either one of those. So sometimes it feels like a game of darts.

Paul48

The standard for NPT was established in the 1860's, so it would have to be a very old fitting to not be replaceable with a new fitting.

ChrisJ

KC,
Yeah that's basically what I'm asking. Right now it applies to the 1 1/4" 45 and 90 I'm about to bust out on that short runout.

Then it occurred to me what about if you replace something like a tee on a steam main assuming you've got a union close by or something. Will a modern tee drop right in, or would it end up a hair too wide or short etc.

Up until now I automatically assumed all of them were slightly different aside from the angle and NPT part then I started thinking perhaps there are standard dimensions.