Comparison Between Latrolet 45 degree Fitting and Weldolet Fitting
author: www.qishine.com
2026-06-11
I. Introduction: Basic Concept of Branch Outlet Fittings
Branch outlet fittings are reinforcement-type fittings used for branch connections on run pipes. Through an integral forging process, reinforcement functionality is incorporated directly into the fitting body, replacing traditional methods such as reducing tees, reinforcement pads, and reinforced pipe sections. All branch outlet fittings comply with the MSS SP-97 international standard, which covers integrally reinforced forged branch fittings with branch angles of 90° and 45°, and includes three end connection types: butt-weld, socket-weld, and threaded. Unlike traditional direct branch welding with reinforcement pads, the forged contour of branch outlet fittings distributes stress uniformly and requires only one weld seam to connect to the run pipe, significantly reducing welding workload and leakage risk.
Branch outlet fittings are reinforcement-type fittings used for branch connections on run pipes. Through an integral forging process, reinforcement functionality is incorporated directly into the fitting body, replacing traditional methods such as reducing tees, reinforcement pads, and reinforced pipe sections. All branch outlet fittings comply with the MSS SP-97 international standard, which covers integrally reinforced forged branch fittings with branch angles of 90° and 45°, and includes three end connection types: butt-weld, socket-weld, and threaded. Unlike traditional direct branch welding with reinforcement pads, the forged contour of branch outlet fittings distributes stress uniformly and requires only one weld seam to connect to the run pipe, significantly reducing welding workload and leakage risk.
The branch outlet fitting body is manufactured from high-quality forgings, with materials including carbon steel (ASTM A105, A350 LF2, etc.), alloy steel (A182 F11/F22, etc.), and stainless steel (A182 F304/F316, etc.). Pressure ratings include 3000#, 6000#, and 9000#. Their key advantage lies in the inherent, fully integrated reinforcement, eliminating the need for additional reinforcement pads. This ensures pressure safety while reducing welding volume by over 30%. They are widely used in high-pressure, high-temperature, and large-diameter thick-wall piping systems across the petroleum, chemical, power, and nuclear power industries.
II. 45° Lateral Branch Outlet Fitting (Latrolet)
Definition and Shape: A 45° Latrolet fitting is a forged fitting used to create a branch connection at a 45° angle from the run pipe. Its base is precisely contoured to match the outer diameter of the run pipe, while the top features a standard butt-weld bevel or a socket-weld/threaded connection, depending on the branch pipe connection method required. It complies with MSS SP-97.
Definition and Shape: A 45° Latrolet fitting is a forged fitting used to create a branch connection at a 45° angle from the run pipe. Its base is precisely contoured to match the outer diameter of the run pipe, while the top features a standard butt-weld bevel or a socket-weld/threaded connection, depending on the branch pipe connection method required. It complies with MSS SP-97.
Latrolet 45 degree installation instruction
Advantages and Disadvantages: The main advantage is superior hydraulic characteristics – compared to a 90° branch, the 45° transition significantly reduces flow turbulence and pressure drop. In high-pressure relief systems and manifolds with specific flow direction requirements, this design reduces erosion-corrosion risk. Disadvantages include the need for an elliptical (rather than circular) hole in the run pipe, requiring precise cutting using layover templates or CNC methods – making installation more difficult than 90° fittings. Additionally, as a non-standard item, lead times are typically longer.
Typical Applications: Primarily used for 45° branch lines, branch points where reduced flow resistance is desired, slurry pipelines requiring reduced erosion, and distribution manifolds in two-phase flow systems.
III. Butt-Weld Branch Outlet Fitting (Weldolet)
Definition and Shape: The butt-weld branch outlet fitting (Weldolet) is the most common and widely used type, providing a 90° branch outlet from the run pipe. Its base is also machined to match the run pipe's curvature. The top features a butt-weld bevel conforming to ASME B16.25, ready for direct butt-welding to the branch pipe. Variants include standard (WOL), swaged (WNL), and elbow (1.5D WEL) types, with size ranges covering DN15 to DN600.
Definition and Shape: The butt-weld branch outlet fitting (Weldolet) is the most common and widely used type, providing a 90° branch outlet from the run pipe. Its base is also machined to match the run pipe's curvature. The top features a butt-weld bevel conforming to ASME B16.25, ready for direct butt-welding to the branch pipe. Variants include standard (WOL), swaged (WNL), and elbow (1.5D WEL) types, with size ranges covering DN15 to DN600.
Weldolet installation instruction
Advantages and Disadvantages: Key advantages include ease of installation, integral reinforcement, high standardization, ready availability, and short delivery times. When the branch-to-run diameter ratio is less than 0.5, Weldolets are a more economical alternative to reducing tees. A disadvantage is that the 90° branch direction creates relatively higher flow turbulence and stress intensification factors, requiring calculation and verification under ASME B31.3 for critical fatigue conditions.
Typical Applications: Widely used in standard 90° branch scenarios, including core process piping in petrochemical plants, high-pressure steam systems, and large cooling water lines. It is the mainstream choice for branch connections.
IV. Comparison Between Latrolet and Weldolet
| Comparison Item | Latrolet | Weldolet |
| Branch Angle | 45° | 90° |
| Run Pipe Hole Shape | Elliptical | Circular |
| Hydraulic Characteristics | Lower pressure drop | Standard |
| Procurement Convenience | Typically custom order, longer lead time | Readily stocked |
| Installation Difficulty | Higher | Standard |
The selection principle is the same as for Weldolets, depending on the branch-to-run diameter ratio: When the ratio is less than 0.5, a branch outlet fitting (Latrolet or Weldolet) is preferred. When the ratio exceeds 0.5, a reducing tee is recommended.
V. Other Common Types of Branch Outlet Fittings
1. Socket-Weld Branch Outlet Fitting (Sockolet): Uses a socket-weld connection for small-diameter branch pipes. Suitable for instrument lines, drain lines, and sample lines in small-bore, high-pressure applications. Size range is 1/2" to 4".
2. Threaded Branch Outlet Fitting (Thredolet): Uses NPT threads for branch connection. Primarily used in utility pipelines, temporary connections, and applications requiring no welding.
3. Elbow Branch Outlet Fitting (Elbolet): Used to create a branch connection on long-radius or short-radius elbows. Suitable for special piping layouts requiring a branch at an elbow location.
1. Socket-Weld Branch Outlet Fitting (Sockolet): Uses a socket-weld connection for small-diameter branch pipes. Suitable for instrument lines, drain lines, and sample lines in small-bore, high-pressure applications. Size range is 1/2" to 4".
2. Threaded Branch Outlet Fitting (Thredolet): Uses NPT threads for branch connection. Primarily used in utility pipelines, temporary connections, and applications requiring no welding.
3. Elbow Branch Outlet Fitting (Elbolet): Used to create a branch connection on long-radius or short-radius elbows. Suitable for special piping layouts requiring a branch at an elbow location.
VI. Relevant Standards and Selection Recommendations
Branch outlet fittings primarily comply with the international standard MSS SP-97. The equivalent Chinese national standard is GB/T 19326 "Forged Branch Outlet Fittings," with the current version being GB/T 19326-2022. Both standards maintain high consistency in dimensions, tolerances, materials, testing, and marking.
Branch outlet fittings primarily comply with the international standard MSS SP-97. The equivalent Chinese national standard is GB/T 19326 "Forged Branch Outlet Fittings," with the current version being GB/T 19326-2022. Both standards maintain high consistency in dimensions, tolerances, materials, testing, and marking.
Selection Recommendations:
Branch-to-run diameter ratio < 0.5: Prefer Weldolet (90°) or Latrolet (45°), depending on installation space and flow direction requirements.
High-pressure, small-bore branch pipe: Choose Sockolet.
Branch at elbow location: Choose Elbolet.
Branch-to-run diameter ratio < 0.5: Prefer Weldolet (90°) or Latrolet (45°), depending on installation space and flow direction requirements.
High-pressure, small-bore branch pipe: Choose Sockolet.
Branch at elbow location: Choose Elbolet.
Mastering the structural forms, manufacturing standards, and application scenarios of the above branch outlet fittings enables efficient design of high-pressure piping systems and achieves cost reduction and efficiency improvement while ensuring safety and reliability.
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Website: www.qishine.com
Email: qishine@qishine.com
Tel: 0592-5225595
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+86 15985833169
Website: www.qishine.com
Email: qishine@qishine.com
Tel: 0592-5225595
WhatsApp: +86 15960259563
+86 15985833169
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