Concentric Reducer dimensions

[CM06]

I need to know the physical dimensions of an 18" x 16" B16.9 concentric reducer. That is, what is the length of the 18" portion up to the transition and, conversely from the other end, how long is the 16" portion up to the transition section. Any body know where I can find this information?

I have contacted some fitting manufacturers but haven't gotten any responses yet. I assume each manufacturer has their own standard but I figured they would all be relatively the same.

Any help is greatly appreciated.

 

[zdas04]

ASME gives length and wall thickness standards and the rest is left up to the manufacturer and they're not really the same from manufacturer to manufacturer. That is why none of the cool Cad fitting libraries have a reasonable facsimile (CadWorx has a simple trapezoid, the rest are not much better) like they have for flanges.

There are an infinite number of angles tangent to the infinite number of possible fillet radii. Infinity squared is kind of a large number of possibilities and I think the world's fabricators have used most of them.

When I've needed a decent representation, I've split the reducer into 3 equal sections and in the middle 1/3 I've connected the small OD to the large OD and the small ID to the large ID. Then I use the 1/2 the radius of the small end minus 1/2 the small end thickness for the fillet radius of the OD and the 1/2 the radius of the small end plus 1/2 thickness for the ID of the fillet on the small end. Do the same thing on the large end and you get a reasonable looking reducer, but I doubt you'll ever buy one that looks exactly like that representation.

David

 

[pennpiper]

06,
Could you please explain why you need this level of detail.

 

[JohnBreen]

As has been stated above the ASME B16.9 Standard for welding fittings only standardizes the end-to-end length, and the "squareness" of the ends to the centerline. The wall thickness and the cone angle ARE NOT STANDARDIZED. The ends of the fitting must have the same wall thickness as the matching straight pipe (to facilitate welding) but away from the weld line the thickness IS NOT STANDARDIZED. ASME B16.9 fittings are pressure rated by proof tests. If you make a weldment (assembly) of piping and fittings of the same schedule - weld a B16.9 reducer between two pieces of straight pipe and weld B16.9 pipe caps on the end and you pressures test the assembly to destruction, the PIPE must fail before the matching fittings would fail. The manufacturers of the fittings are free to make the fittings of varying shape, cone angle and (away from the weld line) varying wall thickness as long as the fitting will pass a burst test.

Regards, John

 

[rts9364]

I have the same problem, CM06. I need dimensions (local wall thicknesses) for a heat transfer analysis. We considered purchasing a reducer and taking measurements, but as others have stated there is no guarantee the reducer used in service will even be close to what we model.

I am reading a study right now done by another company in the mid-1970's where they attempted to solve this problem for a stress model. They took surveys of 12 different fitting manufacturers and found each and every dimension was all over the map, making the statement "None of the dimensions appear to have any geometrically consistent relationship either with each other or with the size designation." (Comforting for someone trying to create a generalized model.) They ended up creating a model based on approximations of the large range of data, which is what I am going to do, I suppose.

It seems like 30 years later we would have solved this problem for people like us doing analyses. But if it ain't broke...

For what it's worth, the model used in the study I mentioned has the OD transition radii both set equal to 0.1*R1 where R1 is the large end pipe outside radius. This is smaller than the radii we've received from our suppliers, so I will use something in between. I'm not sure about the tangent lengths yet.