[TL;DR] Weldolet, Threadolet, and Sockolet are the three main types of forged branch outlet fittings under MSS SP-97 / ASME B16.11, differing mainly in end connection: butt-welded, threaded, and socket-welded. Weldolet suits high-pressure welded piping (up to Sch160); Sockolet fits small-bore socket-weld lines up to 6000# class; Threadolet is used for low-to-medium pressure threaded branch connections. All are available DN15-DN600 (1/2"-24"), in carbon, alloy, and stainless steel forgings, replacing reducing tees and reinforcing pads for safer, lower-stress branch connections.
Why Branch Outlet Selection Matters More Than It Looks
Procurement engineers sizing a new branch connection often default to a reducing tee without checking whether a forged branch outlet fitting would actually perform better and cost less. On high-pressure, high-temperature, or thick-walled pipelines, that choice affects weld integrity, stress concentration around the branch, and long-term leak risk. Getting it wrong means field rework, failed hydrotests, or a fitting that doesn't match the pressure class of the rest of the system. The real question buyers need answered before placing a PO is not "what is a weldolet" but "which of the three olet types fits my connection type, pressure rating, and pipe schedule" - that's the decision this guide is built to support.
Forged, Not Fabricated - Why It's Safer
Branch outlet fittings are machined from a single high-quality forging in the same material grade as the main pipe (carbon steel, alloy steel, or stainless steel), rather than cut and welded from plate. This removes porosity, cavities, and cold-pour defects, and gives the branch a tight grain structure that resists stress concentration far better than a shop-fabricated reducing tee or reinforcing-pad connection.
Where They Replace Reducing Tees
Olet fittings are widely specified on oil & gas gathering lines, refinery and petrochemical units, power plant steam and feedwater piping, and any large-diameter, thick-walled system where a full reducing tee is oversized or where the branch-to-run ratio is too small for a standard tee to be practical or cost-effective.
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Safety & Reliability Integral forging minimizes stress concentration at the branch connection |
Cost Reduction No reinforcing pad calculation or extra fabrication labor required |
Standardized Series Manufactured to MSS SP-97 / GB-T 19326 for predictable interchangeability |
Improved Flow Smooth internal bore reduces turbulence versus a welded-on saddle patch |
Weldolet vs Threadolet vs Sockolet: Side-by-Side Comparison
All three share the same forged, integrally reinforced body - the difference is purely in how the branch pipe connects to the outlet, which is exactly what determines which one fits your project.
| Comparison Point | Weldolet | Threadolet | Sockolet |
| Branch connection type | Butt weld | NPT / BSPT threaded | Socket weld |
| Pressure class | STD, XS, Sch160 | 3000#, 6000# | 3000#, 6000# |
| Typical branch size | DN15-DN600 (1/2"-36") | DN8-DN50 (1/4"-2") | DN8-DN50 (1/4"-2") |
| Best suited for | Main welded piping, large-diameter branch runs | Instrumentation, low-pressure gauge/drain taps needing disassembly | Small-bore high-pressure branch lines, valve or instrument connections |
| Field maintenance | Requires cutting for replacement | Easy to unscrew and replace | Requires cutting for replacement |
4-Step Guide to Selecting the Right Branch Outlet Fitting
Step 1 - Match connection type to your piping method. If both main and branch pipe are welded, specify Weldolet. If the branch needs periodic disassembly for maintenance (e.g., a drain or gauge line), specify Threadolet. If the branch is small-bore and will be socket-welded to instruments or valves, specify Sockolet.
Step 2 - Confirm the pressure class. Threadolet and Sockolet are rated 3000# or 6000#; Weldolet is specified by schedule (STD/XS/Sch160) matching the run pipe wall thickness. Always cross-check against your line's design pressure and temperature.
Step 3 - Verify branch-to-run size ratio. Per MSS SP-97, olet fittings are only valid within a specific run-pipe-to-branch-size range; outside that range a full reducing tee or a reinforcing pad calculation is still required.
Step 4 - Match material and request mill test certificates. The olet body must be the same material grade as the main pipe (A105 carbon steel, A182 alloy/stainless steel, etc.) to avoid galvanic or thermal-expansion mismatch, and MTCs should be requested before shipment.
Branch outlet height datasheet - Baode Steel technical drawing
Why Buyers Source Branch Outlet Fittings From Tianjin Baode Steel
Established in 2006 and renamed Tianjin Baode Steel Co., Ltd. in 2019, the company operates five factories across Tianjin and Cangzhou producing seamless, ERW, LSAW, and SSAW steel pipe alongside forged and stainless/alloy steel pipe fittings.
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2006 Company founded |
5 Factories in Tianjin & Cangzhou |
40+ Countries and regions served |
ISO 9001 / 14001 / 45001 + AAA Credit |
Frequently Asked Questions
What is the maximum pressure class available for a Sockolet branch fitting?
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Sockolet fittings from Baode Steel are supplied in 3000# and 6000# pressure classes per MSS SP-97, with branch sizes from DN8 to DN50 (1/4"-2"), matching most small-bore instrument and valve take-off requirements.
Can a Threadolet be used on a high-pressure steam line?
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Threadolet is generally limited to lower-pressure, smaller branch connections such as gauges or drains because threaded joints are more prone to leakage under thermal cycling; for high-pressure steam branches, a Weldolet or Sockolet is the recommended choice.
What size range of Weldolet does Baode Steel manufacture?
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Weldolet fittings are produced across DN15-DN600 (1/2"-36" outlet, suitable for main pipe DN8-DN900), in STD, XS, and Sch160 wall thickness, covering carbon steel, alloy steel, and stainless steel grades.
Do branch outlet fittings still need a reinforcing pad calculation?
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No - because the olet body is integrally forged and reinforced per MSS SP-97, it eliminates the separate reinforcing-pad design check that a standard reducing tee or fabricated branch connection would otherwise require.
What certifications come with Baode Steel's forged branch outlet fittings?
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Products are manufactured under ISO 9001, ISO 14001, and ISO 45001 management systems, with mill test certificates provided per order and material traceability back to forging heat number.
Choosing between Weldolet, Threadolet, and Sockolet ultimately comes down to matching connection type and pressure class to your piping design - get that right and you avoid both over-spec costs and under-spec failure risk. For projects needing a mix of butt-weld, threaded, and socket-weld branch outlets on the same pipeline, working with one forging supplier also keeps material traceability and lead times consistent across the order.
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