Long & Extra Long Tangent Fittings
Tangent pipe fittings make process piping installations easier than conventional buttweld pipe fittings. Conventional buttweld pipe fittings are in accordance with ANSI B16.9. This specification governs the dimensions, tolerances and “end prep” for standard buttweld fittings. Wrought pipe fittings formed from pipe, in copper-nickel, stainless steel (and rarely, carbon steel) alloys are usually made in accordance with this specification.
What is different about tangent pipe fittings?
The difference is that one end or both ends of the elbow have extra length added. This extra length is not welded on but actually formed integrally in the bending process. Typical tangent lengths are 2″+ but longer (and custom upon request) tangents are available.
What is the same about tangent pipe fittings?
When manufactured, IAW ANSI B16.9, pipe fitting elbows can be LR (Long Radius) 1.5xDIA or SR (Short Radius) 1.0xDIA in both 90 degree form and 45 degree form. Tangent pipe fitting elbows can also be manufactured as LR and SR.
Where should tangent pipe fittings be used?
Tangent pipe fitting elbows are easier to jig (fixture) for welding because you are always welding straight to straight (as opposed to directly to a 90 or 45). Internal weld alignment rings (i.e. backing rings) can only be used with a tangent pipe fitting. However, the fitting ends can be belled (i.e. slip-on) for even easier, stronger welds.
It is common in process piping for fittings to be in close proximity. As a result, with long & extra-long tangent fittings some welds are eliminated. In piping systems requiring radiographic examination, eliminating welds is very cost effective. In systems requiring high purity, the elimination of welds also eliminates areas highly susceptible to contamination. To eliminate welding further, a Tangent fitting can be roller grooved (Sch. 5 and Sch. 10) or cut grooved (Sch. 40 and higher) for installation using mechanical couplings.
Also, a tangent pipe fitting can be welded in place utilizing “slip over” sleeve couplings. This changes the welding type from buttwelding to fillet welding. A good fillet weld can be made, on average, six times faster than a good buttweld. Fillet welds require less skill than traditional buttwelds and are visually verifiable. Only radiograph can verify the integrity of a good buttweld.
In retrofit applications, a buttweld fitting IAW ANSI B16.9 can be cut out and replaced with tangent pipe fittings.
Tangent Tees and Reducers
Tangent pipe fittings are also available as standard or reducing TEEs, and concentric or eccentric reducers. Like tangent elbows, these components are shaped the same as ANSI B16.9 standard dimension pipe fittings but with longer tangents integrally formed into the fitting.