In the field of pipeline engineering, the ASME B16.9 standard serves as the core specification for pipe fitting manufacturing, providing a unified basis for the dimensions, materials, and performance of various butt weld fittings. Among them, the ASME B16.9 Stub End dimensions, valued for its convenience and reliability in pipeline connections, is widely used in industries such as petroleum, chemical, and power generation.
ASME B16.9 defines the technical requirements for butt weld pipe fittings made from carbon steel, alloy steel, and stainless steel, covering dimensions, tolerances, marking, testing, and material properties. In particular, the dimensional accuracy of Lap Joint Stub Ends—including carbon steel stub ends and stainless steel stub ends—directly affects the sealing integrity, pressure-bearing capacity, and overall adaptability of the piping system. Therefore, these parameters are closely monitored by engineers, procurement teams, and construction personnel alike.
In addition to ASME B16.9, the MSS SP-43 standard also applies to Stub Ends and other wrought stainless steel butt weld fittings, particularly for lightweight and corrosion-resistant applications. While ASME B16.9 primarily covers fittings designed for higher pressure and heavier wall thicknesses, MSS SP-43 specifies dimensions for fittings with schedule 5S, 10S, and 40S wall thicknesses, commonly used in low-pressure or non-critical stainless steel piping systems.
By understanding the relationship between ASME B16.9 and MSS SP-43, industry professionals can accurately select the proper Stub End type based on pressure rating, material grade, and installation requirements—ensuring both performance and cost-effectiveness in pipeline design and construction.
Butt Weld Stub End Specification
ASME B16.9 Standard
This Standard covers overall dimensions, tolerances, ratings, testing, and markings for wrought factory-made buttwelding fittings in sizes NPS 1;2 through 48 (DN 15 through 1200).
Generally speaking, the maximum size of a stub end is 24 inches. This is because it is often used with a lap joint flange. According to the ASME B16.5 standard, the maximum size range of a lap joint flange is only 24 inches. Therefore, the size of the stub end is also limited to this range.
A Stub End is a common butt weld pipe fitting typically used with Lap Joint Flanges. One end is designed for butt welding to steel pipes, while the other features a flanged structure for mating with lap joint flanges.
Stub Ends are categorized into Short Pattern and Long Pattern based on length, with dimensions specified by the ASME B16.9 standard.
Long Pattern Stub End Dimensions
| Nominal Size | OD of Cylinder | Length | Radius of Fillet | Diameter of Lap | |||
| DN | NPS | OD | F | R | |||
| Max. | Min. | Long Type | A | B max | G | ||
| 15 | 1/2 | 22.8 | 20.5 | 76 | 3 | 0.8 | 35 |
| 20 | 3/4 | 28.1 | 25.9 | 76 | 3 | 0.8 | 43 |
| 25 | 1 | 35.0 | 32.6 | 102 | 3 | 0.8 | 51 |
| 32 | 1 1/4 | 43.6 | 41.4 | 102 | 5 | 0.8 | 64 |
| 40 | 1 1/2 | 49.9 | 47.5 | 102 | 6 | 0.8 | 73 |
| 50 | 2 | 62.4 | 59.5 | 152 | 8 | 0.8 | 92 |
| 65 | 2 1/2 | 75.3 | 72.2 | 152 | 8 | 0.8 | 105 |
| 80 | 3 | 91.3 | 88.1 | 152 | 10 | 0.8 | 127 |
| 90 | 3 1/2 | 104.0 | 100.8 | 152 | 10 | 0.8 | 140 |
| 100 | 4 | 116.7 | 113.5 | 152 | 11 | 0.8 | 157 |
| 125 | 5 | 144.3 | 140.5 | 203 | 11 | 1.6 | 186 |
| 150 | 6 | 171.3 | 167.5 | 203 | 13 | 1.6 | 216 |
| 200 | 8 | 222.1 | 218.3 | 203 | 13 | 1.6 | 270 |
| 250 | 10 | 277.2 | 272.3 | 254 | 13 | 1.6 | 324 |
| 300 | 12 | 328.0 | 323.1 | 254 | 13 | 1.6 | 381 |
| 350 | 14 | 359.9 | 354.8 | 305 | 13 | 1.6 | 413 |
| 400 | 16 | 411.0 | 405.6 | 305 | 13 | 1.6 | 470 |
| 450 | 18 | 462.0 | 456.0 | 305 | 13 | 1.6 | 533 |
| 500 | 20 | 514.0 | 507.0 | 305 | 13 | 1.6 | 584 |
| 550 | 22 | 565.0 | 558.0 | 305 | 13 | 1.6 | 641 |
| 600 | 24 | 616.0 | 609.0 | 305 | 13 | 1.6 | 692 |
Short Pattern Stub End Dimensions
| Nominal Size | OD of Cylinder | Length | Radius of Fillet | Diameter of Lap | |||
| DN | NPS | OD | F | R | |||
| Max. | Min. | Short Type | A | B max | G | ||
| 15 | 1/2 | 22.8 | 20.5 | 51 | 3 | 0.8 | 35 |
| 20 | 3/4 | 28.1 | 25.9 | 51 | 3 | 0.8 | 43 |
| 25 | 1 | 35.0 | 32.6 | 51 | 3 | 0.8 | 51 |
| 32 | 1 1/4 | 43.6 | 41.4 | 51 | 5 | 0.8 | 64 |
| 40 | 1 1/2 | 49.9 | 47.5 | 51 | 6 | 0.8 | 73 |
| 50 | 2 | 62.4 | 59.5 | 64 | 8 | 0.8 | 92 |
| 65 | 2 1/2 | 75.3 | 72.2 | 64 | 8 | 0.8 | 105 |
| 80 | 3 | 91.3 | 88.1 | 64 | 10 | 0.8 | 127 |
| 90 | 3 1/2 | 104.0 | 100.8 | 76 | 10 | 0.8 | 140 |
| 100 | 4 | 116.7 | 113.5 | 76 | 11 | 0.8 | 157 |
| 125 | 5 | 144.3 | 140.5 | 76 | 11 | 1.6 | 186 |
| 150 | 6 | 171.3 | 167.5 | 89 | 13 | 1.6 | 216 |
| 200 | 8 | 222.1 | 218.3 | 102 | 13 | 1.6 | 270 |
| 250 | 10 | 277.2 | 272.3 | 127 | 13 | 1.6 | 324 |
| 300 | 12 | 328.0 | 323.1 | 152 | 13 | 1.6 | 381 |
| 350 | 14 | 359.9 | 354.8 | 152 | 13 | 1.6 | 413 |
| 400 | 16 | 411.0 | 405.6 | 152 | 13 | 1.6 | 470 |
| 450 | 18 | 462.0 | 456.0 | 152 | 13 | 1.6 | 533 |
| 500 | 20 | 514.0 | 507.0 | 152 | 13 | 1.6 | 584 |
| 550 | 22 | 565.0 | 558.0 | 152 | 13 | 1.6 | 641 |
| 600 | 24 | 616.0 | 609.0 | 152 | 13 | 1.6 | 692 |
Stainless Steel Lap Joint Stub End Tolerance as per ASME B16.9
| DN | NPS | OD | ID | H F | G | R | t |
| 15-65 | 1/2 -21/2 | +1.6 -0.8 | ± 0.8 | ± 2 | 0 -1 | 0 -1 | +1.6 0 |
| 80-90 | 3-31/2 | ± 1.6 | ± 1.6 | ± 2 | 0 -1 | 0 -1 | +1.6 0 |
| 100 | 4 | ± 1.6 | ± 1.6 | ± 2 | 0 -1 | 0 -2 | +1.6 0 |
| 125-200 | 5-8 | +2.4 -1.6 | ± 1.6 | ± 2 | 0 -1 | 0 -2 | +1.6 0 |
| 250-450 | 10-18 | +4.0 -3.2 | ± 3.2 | ± 2 | 0 -2 | 0 -2 | +3.2 0 |
| 500-600 | 20-24 | +6.4 -4.8 | ± 4.8 | ± 2 | 0 -2 | 0 -2 | +3.2 0 |
MSS SP-43 Standard
MSS SP-43 standard lap joint stub ends are available in sizes ranging from NPS ½ to NPS 24. Manufactured from stainless steel, MSS SP-43 stub ends are suitable for use with Schedule 5S and Schedule 10S pipes, while stub ends are compatible with Schedule 40S pipes. MSS Type A stub ends conform to industry specifications for use with standard flat lap flanges.
MSS SP-43 Stub End Dimensions
| Dimensions of Lap-Joint Stub Ends and Caps | |||||
| Dimensions are in inches. | |||||
| NPS | Nominal O. D. at Bevel | Length F | Diameter of Lap G (Nominal & Max.) | Radius of Fillet | |
| A Nominal&Max | B (Max.) | ||||
| 1/2 | 0.84 | 2.00 | 1.38 | 0.12 | 0.03 |
| 3/4 | 1.05 | 2.00 | 1.69 | 0.12 | 0.03 |
| 1 | 1.32 | 2.00 | 2.00 | 0.12 | 0.03 |
| 1 1/4 | 1.66 | 2.00 | 2.50 | 0.19 | 0.03 |
| 1 1/2 | 1.90 | 2.00 | 2.88 | 0.25 | 0.03 |
| 2 | 2.38 | 2.50 | 3.62 | 0.31 | 0.03 |
| 2 1/2 | 2.88 | 2.50 | 4.12 | 0.31 | 0.03 |
| 3 | 3.50 | 2.50 | 5.00 | 0.38 | 0.03 |
| 3 1/2 | 4.00 | 3.00 | 5.50 | 0.38 | 0.03 |
| 4 | 4.50 | 3.00 | 6.19 | 0.44 | 0.03 |
| 5 | 5.56 | 3.00 | 7.31 | 0.44 | 0.06 |
| 6 | 6.62 | 3.50 | 8.50 | 0.50 | 0.06 |
| 8 | 8.62 | 4.00 | 10.62 | 0.50 | 0.06 |
| 10 | 10.75 | 5.00 | 12.75 | 0.50 | 0.06 |
| 12 | 12.75 | 6.00 | 15.00 | 0.50 | 0.06 |
| 14 | 14.00 | 6.00 | 16.25 | 0.50 | 0.06 |
| 16 | 16.00 | 6.00 | 18.50 | 0.50 | 0.06 |
| 18 | 18.00 | 6.00 | 21.00 | 0.50 | 0.06 |
| 20 | 20.00 | 6.00 | 23.00 | 0.50 | 0.06 |
| 24 | 24.00 | 6.00 | 27.25 | 0.50 | 0.06 |
| NOTES: (a) Minimum lap thickness shall not be less than nominal wall thickness. (b) Connect faces of stub ends shall have a modified spiral or concentric serration. (c) These lengths and radii for use with Schedule 40S or thinner pipe. | |||||
Lap Joint Stub End Weights
| Nominal Size | Sch10S | Sch40S | Sch80S | ||||
| DN | NPS | Long Pattern | Short Pattern | Short Pattern | Long Pattern | Short Pattern | Long Pattern |
| 15 20 25 | 1/2 3/4 1 | 0.07 0.09 0.15 | 0.09 0.12 0.25 | 0.09 0.12 0.18 | 0.12 0.16 0.32 | 0.12 0.15 0.24 | 0.16 0.21 0.43 |
| 32 40 50 | 11/4 11/2 2 | 0.19 0.22 0.35 | 0.34 0.39 0.71 | 0.25 0.31 0.52 | 0.43 0.52 1.02 | 0.33 0.43 0.73 | 0.57 0.75 1.49 |
| 65 80 90 | 21/2 3 31/2 | 0.46 0.62 0.70 | 0.95 1.22 1.36 | 0.81 1.10 1.52 | 1.60 2.11 2.55 | 1.10 1.50 2.09 | 2.22 2.98 3.65 |
| 100 125 150 | 4 5 6 | 0.94 1.30 1.75 | 1.59 2.80 3.30 | 1.80 2.25 3.59 | 3.05 5.42 7.02 | 2.58 3.60 5.76 | 4.44 7.86 11.3 |
| 200 250 300 | 8 10 12 | 2.90 4.79 7.20 | 4.95 8.50 10.9 | 5.98 10.2 14.9 | 10.6 18.4 22.8 | 9.18 13.7 19.5 | 16.2 24.9 30.2 |
| 350 400 450 | 14 16 18 | 7.95 9.50 11.1 | 15.0 17.3 19.8 | 15.8 18.9 22.0 | 28.7 33.1 38.0 | 21.6 25.2 29.3 | 38.6 44.5 51.1 |
| 500 550 600 | 20 22 24 | 14.1 16.5 19.8 | 25.9 28.2 35.0 | 24.3 – 29.6 | 42.3 – 51.2 | 32.6 – 39.7 | 56.8 – 68.8 |
Stub End Material
Stainless Steel Buttweld Long Stub End :
ASTM A403 WP316/316L, ASTM A403 SA / A 774 WP-S, WP-W, WP-WX 304/304L, ASTM A182 F316L, 304L, DIN 1.4301, DIN1.4306, DIN 1.4401, DIN 1.4404
Duplex & Super Duplex Steel Buttweld Long Stub End :
ASTM A 815, ASME SA 815 UNS NO S31803, S32205. UNS S32750, S32950. Werkstoff No. 1.4462
Carbon Steel Buttweld Long Stub End :
ASTM A234, ASME SA234 WPB , WPBW, WPHY 42, WPHY 46, WPHY 52, WPH 60, WPHY 65 & WPHY 70.
Low Temperature Carbon Steel Buttweld Long Stub End :
ASTM A420 WPL3/WPL6
Alloy Steel Buttweld Long Stub End :
ASTM / ASME A/SA 234 Gr. WP 1, WP 5, WP 9, WP 11, WP 12, WP 22, WP 91
Nickel Alloy Buttweld Long Stub End :
ASTM B336, ASME SB336, Nickel 200 (UNS No. No2200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No. N10276), Alloy 20 (UNS No. N08020), Titanium (Grade I & II), Cupro-Nickel 70/30, CuNi10Fe1Mn, CuNi30Mn1Fe.