MSS SP-97 ASTM A105 / A105N Weldolet & Threadolet | Socket Weld Branch Outlet Fittings
We are a professional manufacturer and exporter of ASTM A105 Weldolet, A105N Weldolet, A105 Threadolet, and Socket Weld Olet in China, providing integrally reinforced forged branch outlet fittings for petroleum, chemical, power, shipbuilding, and industrial applications worldwide.
What is a Weldolet / Threadolet?
- Weldolet: A branch connection with a butt-weld end used to create a reinforced lateral connection on a pressure pipe.
- Threadolet: A threaded branch outlet allowing connection without welding.
- Socket Weld Olet: A socket-welded branch outlet providing strong, leak-proof connections.
These fittings allow branching from main pipelines while maintaining strength and pressure integrity.
Material Standards
| Material Type | Standard |
|---|---|
| Carbon Steel | ASTM A105, A105N, ASTM A350 LF2 |
| Alloy Steel | ASTM A182 F11, F22, F12, F5, F9, F91 |
| Stainless Steel | ASTM A182 F304/F304L, F316/F316L, F321/F321H, F347/F347H, S31803 Duplex, S32750 Super Duplex |
| Line Pipe Compatibility | ASTM A694 F42, F46, F52, F56, F60, F65, F70 |
| Special Alloys | Monel, Inconel, Alloy 20, Nickel Alloy, 904L |
Type & Application
- Available Types: Weldolet, Threadolet, Socket Weld Olet
- Sizes: 1/2″ – 60″ (DN15 – DN1500)
- Wall Thickness: SCH 40 – SCH XXS
- Pressure Ratings: 2000#, 3000#, 6000#, 9000#
- Application: Petroleum, chemical, power plants, shipbuilding, nuclear, urban construction, hot-water systems, fire prevention, metallurgy, aerospace.
Standards & Specifications
- ASME / ANSI: B16.11 – Forged Fittings Socket-Welding and Threaded
- MSS: SP-97 – Integrally Reinforced Forged Branch Outlet Fittings
- Material Test Certificates: EN10204 3.1 available
ASTM A105 / A105N Chemical Composition
| Element | Max / Range |
|---|---|
| Carbon (C) | 0.15% max |
| Manganese (Mn) | 0.6–1.05% |
| Phosphorus (P) | 0.035% max |
| Sulfur (S) | 0.04% max |
| Silicon (Si) | 0.1% min |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 485 MPa |
| Yield Strength | 250 MPa |
| Elongation | 30% |
Features & Benefits
- Integrally reinforced branch outlet ensures high-pressure performance
- Available in carbon steel, alloy steel, stainless steel, and special alloys
- Suitable for high-temperature and corrosive environments
- Butt-weld, socket-weld, and threaded connection options
- Fully tested and certified for industrial and marine applications
How to Order
Example 1: ASTM A105 Weldolet
- Type: Weldolet, Butt Weld
- Size: 4″ × 2″
- Schedule: SCH 80
- Pressure: 3000#
- Material: ASTM A105
- Standard: MSS SP-97 / ASME B16.11
- Quantity: 50 PCS
Example 2: A105N Threadolet
- Type: Threadolet, Threaded
- Size: 2″ × 1/2″
- Schedule: SCH 40
- Pressure: 2000#
- Material: ASTM A105N
- Standard: MSS SP-97 / ASME B16.11
- Quantity: 30 PCS
Applications
- Petroleum & Gas Pipelines: High-pressure branch connections
- Chemical Industry: Corrosion-resistant lateral piping
- Power & Energy Plants: High-temperature and pressure piping
- Shipbuilding & Marine: Reinforced branch outlets for seawater and fuel lines
- Nuclear & Aerospace: High-integrity, high-strength branch connections
MSS SP-97-2019
Integrally Reinforced Forged Branch Outlet Fittings – Socket Welding, Threaded and Buttwelding Ends
MSS SP-97-2019 includes essential dimensions, finish, tolerances, testing, marking, material, and minimum strength requirements for 90° and 45° integrally reinforced forged branch outlet fittings of buttwelding, socket welding, and threaded types.
Unless specified otherwise by the manufacturer, conventional integrally reinforced forged branch outlet fittings are intended for the following header by branch combinations: STD × STD, XS × XS, SCH. 160 × SCH 160, XXS × XXS, XS × 3000, SCH 160 × 6000, and XXS × 9000. When the run and branch pipes are of differing or mixed schedules, then the selection of the branch connection shall be determined by contacting the manufacturer. Such selections shall be agreed upon by purchaser and manufacturer at time of order and may involve supplemental marking requirements determined by other standards (e.g., material grade determination, other factors). See Section 1.3. Mixed schedule branch outlet fittings are unique to the design of each system, and thus outside the scope of this Standard Practice. The adequacy of the design for light, intermediate, and heavy wall branch outlet fittings may be established by mathematical analysis as contained in the applicable pressure vessel or piping codes, or by finite element analysis.

Dimensions Size on Size Weldolet STD – MSS SP97
| NPS | A | B | C | D | L | |
| 1/2 | INCH MM |
3/4 19.05 |
1-3/8 34.93 |
15/16 23.81 |
5/8 15.88 |
1-3/16 30.16 |
| 3/4 | INCH MM |
7/8 22.23 |
1-5/8 41.28 |
1-3/16 30.16 |
13/16 20.64 |
1-7/16 36.51 |
| 1 | INCH MM |
1-1/16 26.99 |
2 50.80 |
1-7/16 36.51 |
1-1/32 26.19 |
1-1/16 26.99 |
| 1¼ | INCH MM |
1-1/4 31.75 |
2-3/8 60.3 |
1-3/4 44.45 |
1-3/8 34.93 |
2-1/16 52.39 |
| 1½ | INCH MM |
1-5/16 33.34 |
2-7/8 73 |
2 50.80 |
1-5/8 41.28 |
2-1/4 57.15 |
| 2 | INCH MM |
1-1/2 38.10 |
3-1/2 88.90 |
2-9/16 65.09 |
2-1/16 52.39 |
2-11/16 68.26 |
| 2½ | INCH MM |
1-5/8 41.28 |
4-1/16 103.19 |
3 76.20 |
2-7/16 61.91 |
3-1/16 77.79 |
| 3 | INCH MM |
1-3/4 44.45 |
4-13/16 122.24 |
3-11/16 93.66 |
3-1/16 77.79 |
3-1/2 88.90 |
| 3½ | INCH MM |
2 50.80 |
5-3/8 136.53 |
3-7/8 98.43 |
3-9/16 90.49 |
3-7/8 98.43 |
| 4 | INCH MM |
2 50.80 |
6 152.40 |
4-3/4 120.65 |
4 101.60 |
4-1/4 107.95 |
| 5 | INCH MM |
2-1/4 57.15 |
7-1/8 180.98 |
5-9/16 141.29 |
5-1/16 128.59 |
5-1/16 128.59 |
| 6 | INCH MM |
2-3/8 60.3 |
8-1/2 215.90 |
6-11/16 169.86 |
6-1/16 153.99 |
5-11/16 144.46 |
| 8 | INCH MM |
2-3/4 69.85 |
10-3/8 263.53 |
8-11/16 220.66 |
7-15/16 201.61 |
7-1/16 179.39 |
| 10 | INCH MM |
3-1/16 77.79 |
12-9/16 319.09 |
10-13/16 274.64 |
10 254.00 |
8-7/16 214.31 |
| 12 | INCH MM |
3-3/8 85.73 |
14-7/8 377.83 |
12-13/16 325.44 |
12 304.80 |
9-3/4 247.65 |
| 14 | INCH MM |
3-1/2 88.90 |
16-1/8 409.58 |
14-1/16 357.19 |
13-1/4 336.55 |
10-1/2 266.70 |
| 16 | INCH MM |
3-11/16 93.66 |
18-1/4 463.55 |
16-1/16 407.99 |
15-1/4 387.35 |
11-11/16 296.86 |
| 18 | INCH MM |
4-1/16 103.19 |
20-3/4 527.05 |
18-5/8 473.08 |
17-1/4 438.15 |
13-1/16 331.79 |
| 20 | INCH MM |
4-5/8 117.48 |
23-1/16 585.79 |
20-1/16 509.59 |
19-1/4 488.95 |
14-5/8 371.48 |
| 24 | INCH MM |
5-3/8 136.53 |
27-7/8 708.03 |
25-1/8 638.18 |
23-1/4 590.55 |
17-3/8 441.33 |
| NPS | A | B | C | D | L |
Dimensions Weldolet Reducing – STD – MSS SP97

| NPS | A | B | C | |
| 1/2 | INCH MM |
3/4 19.05 |
1-3/8 34.93 |
15/16 23.81 |
| 3/4 | INCH MM |
7/8 22.23 |
1-3/4 44.45 |
1-3/16 30.16 |
| 1 | INCH MM |
1-1/16 26.99 |
2-1/8 53.98 |
1-7/16 36.51 |
| 1¼ | INCH MM |
1-1/4 31.75 |
2-9/16 65.09 |
1-3/4 44.45 |
| 1½ | INCH MM |
1-5/16 33.34 |
2-7/8 73 |
2 50.80 |
| 2 | INCH MM |
1-1/2 38.10 |
3-1/2 88.90 |
2-9/16 65.09 |
| 2½ | INCH MM |
1-5/8 41.28 |
4-1/16 103.19 |
3 76.20 |
| 3 | INCH MM |
1-3/4 44.45 |
4-13/16 122.24 |
3-11/16 93.66 |
| 3½ | INCH MM |
1-7/8 47.63 |
5-5/8 142.88 |
4 101.60 |
| 4 | INCH MM |
2 50.80 |
6 152.40 |
4-3/4 120.65 |
| 5 | INCH MM |
2-1/4 57.15 |
7-1/16 179.39 |
5-9/16 141.29 |
| 6 | INCH MM |
2-3/8 60.3 |
8-1/2 215.90 |
6-11/16 169.86 |
| 8 | INCH MM |
2-3/4 69.85 |
10-3/8 263.53 |
8-11/16 220.66 |
| 10 | INCH MM |
3-1/16 77.79 |
12-11/16 322.26 |
10-13/16 274.64 |
| 12 | INCH MM |
3-3/8 85.73 |
14-7/8 377.83 |
12-13/16 325.44 |
| 14 | INCH MM |
3-1/2 88.90 |
16-1/8 409.58 |
14-1/16 357.19 |
| 16 | INCH MM |
3-11/16 93.66 |
18-1/4 463.55 |
16-1/16 407.99 |
| 18 | INCH MM |
3-13/16 96.84 |
20-1/2 520.70 |
18-1/16 458.79 |
| 20 | INCH MM |
4 101.60 |
22-1/2 571.50 |
20 508.00 |
| 24 | INCH MM |
4-9/16 115.89 |
27-1/8 688.98 |
24-3/16 614.36 |
| NPS | A | B | C |
Dimensions (L) Center Line of Run Pipe to Face of Weldolet
| NPS | Outlet Sizes STD and XS NPS 1/2 – 4 | ||||||||||
| 1/2 | 3/4 | 1 | 11/4 | 11/2 | 2 | 21/2 | 3 | 31/2 | 4 | ||
| 3/4 | INCH MM |
1-1/4 31.75 |
|||||||||
| 1 | INCH MM |
1-3/8 34.92 |
1-1/2 38.10 |
||||||||
| 1¼ | INCH MM |
1-9/16 39.68 |
1-11/16 42.86 |
1-7/8 47.62 |
|||||||
| 1½ | INCH MM |
1-11/16 42.86 |
1-13/16 46.03 |
2 50.80 |
2-3/16 55.56 |
||||||
| 2 | INCH MM |
1-15/16 49.21 |
2-1/16 52.38 |
2-1/4 57.15 |
2-7/16 61.91 |
2-1/2 63.50 |
|||||
| 2½ | INCH MM |
2-3/16 55.56 |
2-5/16 58.73 |
2-1/2 63.50 |
2-11/16 68.26 |
2-3/4 69.85 |
2-15/16 74.61 |
||||
| 3 | INCH MM |
2-1/2 63.5 |
2-5/8 66.67 |
2-13/16 71.43 |
3 76.20 |
3-1/16 77.78 |
3-1/4 82.55 |
3-3/8 85.72 |
|||
| 3½ | INCH MM |
2-3/4 69.85 |
2-7/8 73.02 |
3-1/16 77.78 |
3-1/4 82.55 |
3-5/16 84.13 |
3-1/2 88.9 |
3-5/8 92.07 |
3-3/4 95.25 |
||
| 4 | INCH MM |
3 76.2 |
3-1/8 79.37 |
3-5/16 84.13 |
3-1/2 88.90 |
3-9/16 90.48 |
3-3/4 95.25 |
3-7/8 98.42 |
4 101.60 |
4-1/8 104.77 |
|
| 5 | INCH MM |
3-9/16 90.48 |
3-11/16 93.66 |
3-7/8 98.42 |
4-1/16 103.18 |
4-1/8 104.77 |
4-5/16 109.53 |
4-7/16 112.71 |
4-9/16 115.88 |
4-11/16 119.06 |
4-13/16 122.23 |
| 6 | INCH MM |
4-1/16 103.18 |
4-3/16 106.36 |
4-3/8 111.12 |
4-9/16 115.88 |
4-5/8 117.47 |
4-13/16 122.23 |
4-15/16 125.41 |
5-1/16 128.58 |
5-3/16 131.76 |
5-5/16 134.93 |
| 8 | INCH MM |
5-1/16 128.58 |
5-3/16 131.76 |
5-3/8 136.52 |
5-9/16 141.28 |
5-5/8 142.87 |
5-13/16 147.63 |
5-15/16 150.81 |
6-1/16 153.98 |
6-3/16 157.16 |
6-5/16 160.3 |
| 10 | INCH MM |
6-1/8 155.57 |
6-1/4 158.75 |
6-7/16 163.51 |
6-5/8 168.27 |
6-11/16 169.86 |
6-7/8 174.62 |
7 177.8 |
7-1/8 180.97 |
7-1/4 184.15 |
7-3/8 187.32 |
| 12 | INCH MM |
7-1/8 180.97 |
7-1/4 184.15 |
7-7/16 188.91 |
7-5/8 193.67 |
7-11/16 195.26 |
7-7/8 200.02 |
8 203.20 |
8-1/8 206.37 |
8-1/4 209.55 |
8-3/8 212.72 |
| 14 | INCH MM |
7-3/4 196.85 |
7-7/8 200.02 |
8-1/16 204.78 |
8-1/4 209.55 |
8-5/16 211.13 |
8-1/2 215.90 |
8-5/8 219.07 |
8-3/4 222.25 |
8-7/8 225.42 |
9 228.60 |
| 16 | INCH MM |
8-3/4 222.25 |
8-7/8 225.42 |
9-1/16 230.18 |
9-1/4 234.95 |
9-5/16 236.53 |
9-1/2 241.30 |
9-5/8 244.47 |
9-3/4 247.65 |
9-7/8 250.82 |
10 254.00 |
| 18 | INCH MM |
9-3/4 247.65 |
9-7/8 250.82 |
10-1/16 255.58 |
10-1/4 260.35 |
10-5/16 261.93 |
10-1/2 266.70 |
10-5/8 269.87 |
10-3/4 273 |
10-7/8 276.22 |
11 279.40 |
| 20 | INCH MM |
10-3/4 273 |
10-7/8 276.22 |
11-1/16 280.98 |
11-1/4 285.75 |
11-5/16 287.33 |
11-1/2 292.10 |
11-5/8 295.27 |
11-3/4 298.45 |
11-7/8 301.62 |
12 304.80 |
| 24 | INCH MM |
12-3/4 323.9 |
12-7/8 327.02 |
13-1/16 331.78 |
13-1/4 336.55 |
13-5/16 338.13 |
13-1/2 342.90 |
13-5/8 346.07 |
13-3/4 349.25 |
13-7/8 352.42 |
14 355.60 |
| NPS | 1/2 | 3/4 | 1 | 11/4 | 11/2 | 2 | 21/2 | 3 | 31/2 | 4 | |
| Outlet Sizes STD and XS NPS 1/2 – 4 | |||||||||||
Dimensions (L) Center Line of Run Pipe to Face of Weldolet
| NPS | Outlet Size STD NPS 5 – 20 | |||||||||
| 5 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | ||
| 6 | INCH MM |
5-9/16 141.28 |
||||||||
| 8 | INCH MM |
6-9/16 166.68 |
6-11/16 169.86 |
|||||||
| 10 | INCH MM |
7-5/8 193.67 |
7-3/4 196.85 |
8-1/8 206.37 |
||||||
| 12 | INCH MM |
8-5/8 219.07 |
8-3/4 222.25 |
9-1/8 231.77 |
9-7/16 239.71 |
|||||
| 14 | INCH MM |
9-1/4 234.95 |
9-3/8 238.12 |
9-3/4 247.65 |
10-1/16 255.58 |
10-3/8 263.52 |
||||
| 16 | INCH MM |
10-1/4 260.35 |
10-3/8 263.52 |
10-3/4 273 |
11-1/16 280.98 |
11-3/8 288.92 |
11-1/2 292.10 |
|||
| 18 | INCH MM |
11-1/4 285.75 |
11-3/8 288.92 |
11-3/4 298.45 |
12-1/16 306.38 |
12-3/8 314.32 |
12-1/2 317.50 |
12-11/16 322.26 |
||
| 20 | INCH MM |
12-1/4 311.15 |
12-3/8 314.32 |
12-3/4 323.9 |
13-1/16 331.78 |
13-3/8 339.72 |
13-1/2 342.90 |
13-11/16 347.66 |
13-13/16 350.83 |
|
| 24 | INCH MM |
14-1/4 361.95 |
14-3/8 365.12 |
14-3/4 374.65 |
15-1/16 382.58 |
15-3/8 390.52 |
15-1/2 393.70 |
15-11/16 398.46 |
15-13/16 401.63 |
16 406.40 |
| NPS | 5 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | |
| Outlet Size STD NPS 5 – 20 | ||||||||||
General notes:
- Root Gap – X – “Space” for welding the O’let is raised off the run pipe to establish proper weld gap by placing spacers, e.g. welding rods, under the fitting. This provides a uniform welding gap between the curvature of the run and base of fitting.
- X = Root Gap not included in L measure.
- L = Dimensions Center Line of Run Pipe to Face of Weldolet.
- Bevelled Ends ASME B16.9 and B16.25.
Please send inquiry to bill@cnpipefitting.com
