MSS SP-97 covers integrally reinforced forged branch outlets — the weldolet, sockolet, threadolet and their variants. They replace a tee where the run pipe is not cut: the outlet is welded to the outside of the run and the branch is made from it. The standard fixes the reinforcement, the branch connection and the marking; the run size and branch size are stated separately on every order.
The SP-97 family
| Type | Branch connection | Where it is used |
|---|---|---|
| Weldolet | Butt weld to the branch pipe | Standard branch on carbon, alloy and stainless run pipe |
| Sockolet | Socket weld, ASME B16.11 | Small bore branch where a socket joint is specified |
| Threadolet | Threaded NPT, ASME B16.11 | Small bore instrument and utility branch, no hot work on the branch |
| Elbolet | Butt weld or socket | Branch on an elbow, where a tee will not fit |
| Latrolet | Butt weld or socket | 45° branch take-off |
| Nipolet | Threaded or plain | Small drain, vent or instrument connection |
How the size is written
An outlet is ordered as run size x branch size, for example 8 x 2 in weldolet: 8 in is the run pipe outside diameter the outlet sits on, 2 in is the branch. For a butt weld outlet the branch wall follows the branch pipe schedule; for a socket or threaded outlet the class (3000 or 6000) follows ASME B16.11.
| Parameter | What to state |
|---|---|
| Run size | The outside diameter of the run pipe, in NPS or mm |
| Branch size | The branch NPS, and the branch schedule for a butt weld outlet |
| Connection | Butt weld, socket weld or threaded |
| Class | 3000 or 6000 for socket and threaded outlets |
| Grade | A105, A182 F304/F316, A350 LF2, or the grade that matches the run pipe |
Where olets go wrong
The two recurring errors are a branch ordered without its schedule, and a run size given as the pipe nominal size when the outlet is made to the outside diameter. A third is a socket outlet specified on a line that will be radiographed: the socket joint cannot be examined the way a butt weld can. State the connection and the examination requirement together.
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Related pages
Olets and branch connections · ASME B16.11 · Butt weld fittings
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