What Is a Latrolet?
The name “latrolet” derives from “lateral outlet.” Like all o-let fittings, the header side contours to match the header pipe OD, while the branch end provides a standard butt weld bevel per ASME B16.25.
Latrolet Specifications
| Property | Detail |
|---|---|
| Standard | MSS SP-97 |
| Branch angle | 45° to header |
| Branch end | Butt weld bevel (per ASME B16.25) |
| Header end | Contoured to match header OD |
| Size range | Header: NPS 2 to NPS 36; Branch: NPS 1/2 to NPS 18 |
| Materials | ASTM A105 (CS), A182 F304/F316/F11/F22 (alloy/SS), A350 LF2 (low-temp) |
| Reinforcement | Integral |
Latrolet vs Lateral Tee
| Feature | Latrolet | Lateral Tee |
|---|---|---|
| Branch angle | 45° | 45° |
| Branch/header ratio | < 0.5 (typically) | 0.5 to 1.0 |
| Fitting type | Forged branch outlet | Factory-made BW fitting |
| Header modification | Hole cut in header | Replaces section of header |
| Standard | MSS SP-97 | ASME B16.9 |
| Cost (small branch) | Lower | Higher (full tee body) |
| Reinforcement | Integral | Integral (tee body) |
The selection follows the same branch-to-header ratio logic as weldolets vs reducing tees. Below a 0.5 ratio, a latrolet is more economical than a reducing lateral tee. Above 0.5, the lateral tee provides a stronger, more standardized connection.
Applications
Latrolets serve specific process and pipeline needs:
- Pipeline branch connections: 45-degree takeoffs on transmission pipelines for reduced flow turbulence
- Header manifolds: Angled branches on distribution headers where flow direction matters
- Slurry lines: Reduced erosion at branch junctions compared to 90-degree weldolets
- Two-phase flow systems: Smoother branch entry reduces phase separation
- Fire water deluge systems: Angled nozzle connections on ring headers
Latrolet vs Weldolet
| Feature | Latrolet (45°) | Weldolet (90°) |
|---|---|---|
| Branch angle | 45° | 90° |
| Pressure drop | Lower (angled entry) | Higher (perpendicular entry) |
| Flow disturbance | Less | More |
| Stress concentration | Lower SIF | Higher SIF |
| Availability | Less common | Widely stocked |
| Lead time | Longer (often made to order) | Shorter (ex-stock) |
Installation
Installation follows the same procedure as other o-let fittings:
- Mark the branch location on the header at the correct 45-degree orientation
- Cut an elliptical hole in the header (the 45-degree angle produces an oval opening, not circular)
- Fit the contoured base of the latrolet to the header surface
- Weld with a full-penetration groove weld around the base
- Butt weld the branch pipe to the latrolet outlet
The elliptical hole shape requires precise layout. Template cutting or CNC pipe profiling ensures accuracy. The weld at the header junction is inspected per the piping specification, with radiographic or ultrasonic testing for critical services.
For a complete dimensional reference of branch connection fittings, see weldolet/elbolet/sockolet sizes.
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