Lap Joint Stub End Dimensions
A stub end butt welds right to the pipe and makes dat lapped face dat seals up the joint. The lap joint flange slides on behind the lap and bolts clear through to the flange on the other side of the joint, not to the stub end itself. Only dat stub end touches your process; the backing flange stays loose behind the lap and don't never see a drop of dat fluid.
Why the pair exists.
Since dat backin' flange don't get wet, y'all can use a cheaper material than the pipe itself. On them stainless or alloy systems, dat's the whole point: a stainless stub end with a carbon steel backin' flange gives you dat corrosion resistance right where it matters, and it won't cost you near as much as a solid alloy flange.
Bolt holes dat swing.
Dat loose backin' flange just rotates freely till the joint is made up, so y'all can align dem bolt holes right on site without havin' to spin the pipe. On large-diameter and awkward field fit-ups, dat right there can justify the joint, which is why lap joints are mighty common on tank nozzles and equipment connections that gotta come apart regular-like.
How To Read Dese Dimensions
The tables below are MSS SP-43 Type A, the long pattern, whose dimensions follow ASME B16.9. MSS SP-43 also defines a Type B short pattern and a Type C reducin' pattern, and the overall length J differs between 'em. Make sure y'all confirm which type the spool was drawn around before orderin'.
- T
- Wall and lap thicknessNominal wall at the weldin' end, which is also the thickness of the lap.
- K
- Lap diameterDiameter across the lapped face. It's gotta suit dat backing flange sittin' right behind it.
- N
- Fillet radiusRadius at the back of the lap. Dat backin' flange bears right against this face, so its bore has gotta clear the radius.
- J
- Overall lengthWeldin' face to the face of the lap. Now, this is the dimension that's different between dat Type A long pattern and the Type B short pattern.
113 sizes across 6 schedules · dimensions in inches, weights in pounds · MSS SP-43 Type A
Schedule STD
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.109 | 1.38 | 0.12 | 3.00 | 40 | 0.30 |
| ¾ | 1.106 | 1.019 | 0.113 | 1.69 | 0.12 | 3.00 | 40 | 0.40 |
| 1 | 1.376 | 1.284 | 0.133 | 2.00 | 0.12 | 4.00 | 40 | 0.75 |
| 1¼ | 1.716 | 1.629 | 0.140 | 2.50 | 0.19 | 4.00 | 40 | 1.10 |
| 1½ | 1.965 | 1.869 | 0.145 | 2.88 | 0.25 | 4.00 | 40 | 1.25 |
| 2 | 2.456 | 2.344 | 0.154 | 3.62 | 0.31 | 6.00 | 40 | 2.25 |
| 2½ | 2.966 | 2.844 | 0.203 | 4.12 | 0.31 | 6.00 | 40 | 3.50 |
| 3 | 3.596 | 3.469 | 0.216 | 5.00 | 0.38 | 6.00 | 40 | 4.75 |
| 3½ | 4.096 | 3.969 | 0.226 | 5.50 | 0.38 | 6.00 | 40 | 6.00 |
| 4 | 4.593 | 4.469 | 0.237 | 6.19 | 0.44 | 6.00 | 40 | 7.25 |
| 5 | 5.683 | 5.532 | 0.258 | 7.31 | 0.44 | 8.00 | 40 | 12.00 |
| 6 | 6.743 | 6.594 | 0.280 | 8.50 | 0.50 | 8.00 | 40 | 16.00 |
| 8 | 8.743 | 8.594 | 0.322 | 10.62 | 0.50 | 8.00 | 40 | 23.00 |
| 10 | 10.913 | 10.719 | 0.365 | 12.75 | 0.50 | 10.00 | 40 | 36.00 |
| 12 | 12.913 | 12.719 | 0.375 | 15.00 | 0.50 | 10.00 | * | 47.00 |
| 14 | 14.170 | 13.969 | 0.375 | 16.25 | 0.50 | 12.00 | 30 | 35.40 |
| 16 | 16.180 | 15.969 | 0.375 | 18.50 | 0.50 | 12.00 | 30 | 44.80 |
| 18 | 18.190 | 17.969 | 0.375 | 21.00 | 0.50 | 12.00 | * | 57.20 |
| 20 | 20.240 | 19.969 | 0.375 | 23.00 | 0.50 | 12.00 | 20 | 71.00 |
| 24 | 24.240 | 23.969 | 0.375 | 27.25 | 0.50 | 12.00 | 20 | 102.00 |
Schedule XS
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.147 | 1.38 | 0.12 | 3.00 | 80 | 0.38 |
| ¾ | 1.106 | 1.019 | 0.154 | 1.69 | 0.12 | 3.00 | 80 | 0.51 |
| 1 | 1.376 | 1.284 | 0.179 | 2.00 | 0.12 | 4.00 | 80 | 1.00 |
| 1¼ | 1.716 | 1.629 | 0.191 | 2.50 | 0.19 | 4.00 | 80 | 1.25 |
| 1½ | 1.965 | 1.869 | 0.200 | 2.88 | 0.25 | 4.00 | 80 | 1.75 |
| 2 | 2.456 | 2.344 | 0.218 | 3.62 | 0.31 | 6.00 | 80 | 3.00 |
| 2½ | 2.966 | 2.844 | 0.276 | 4.12 | 0.31 | 6.00 | 80 | 4.50 |
| 3 | 3.596 | 3.469 | 0.300 | 5.00 | 0.38 | 6.00 | 80 | 6.50 |
| 3½ | 4.096 | 3.969 | 0.318 | 5.50 | 0.38 | 6.00 | 80 | 7.75 |
| 4 | 4.593 | 4.469 | 0.337 | 6.19 | 0.44 | 6.00 | 80 | 9.50 |
| 5 | 5.683 | 5.532 | 0.375 | 7.31 | 0.44 | 8.00 | 80 | 17.00 |
| 6 | 6.743 | 6.594 | 0.432 | 8.50 | 0.50 | 8.00 | 80 | 23.00 |
| 8 | 8.743 | 8.594 | 0.500 | 10.62 | 0.50 | 8.00 | 80 | 32.00 |
| 10 | 10.913 | 10.719 | 0.500 | 12.75 | 0.50 | 10.00 | 60 | 53.00 |
| 12 | 12.913 | 12.719 | 0.500 | 15.00 | 0.50 | 10.00 | * | 62.00 |
| 14 | 14.170 | 13.969 | 0.500 | 16.25 | 0.50 | 12.00 | * | 89.00 |
| 16 | 16.180 | 15.969 | 0.500 | 18.50 | 0.50 | 12.00 | 40 | 96.00 |
| 18 | 18.190 | 17.969 | 0.500 | 21.00 | 0.50 | 12.00 | * | 112.00 |
| 20 | 20.240 | 19.969 | 0.500 | 23.00 | 0.50 | 12.00 | 30 | 125.00 |
| 24 | 24.240 | 23.969 | 0.500 | 27.25 | 0.50 | 12.00 | * | 151.00 |
Schedule 40
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.109 | 1.38 | 0.12 | 3.00 | 40 | 0.30 |
| ¾ | 1.106 | 1.019 | 0.113 | 1.69 | 0.12 | 3.00 | 40 | 0.40 |
| 1 | 1.376 | 1.284 | 0.133 | 2.00 | 0.12 | 4.00 | 40 | 0.75 |
| 1¼ | 1.716 | 1.629 | 0.140 | 2.50 | 0.19 | 4.00 | 40 | 1.10 |
| 1½ | 1.965 | 1.869 | 0.145 | 2.88 | 0.25 | 4.00 | 40 | 1.25 |
| 2 | 2.456 | 2.344 | 0.154 | 3.62 | 0.31 | 6.00 | 40 | 2.25 |
| 2½ | 2.966 | 2.844 | 0.203 | 4.12 | 0.31 | 6.00 | 40 | 3.50 |
| 3 | 3.596 | 3.469 | 0.216 | 5.00 | 0.38 | 6.00 | 40 | 4.75 |
| 3½ | 4.096 | 3.969 | 0.226 | 5.50 | 0.38 | 6.00 | 40 | 6.00 |
| 4 | 4.593 | 4.469 | 0.237 | 6.19 | 0.44 | 6.00 | 40 | 7.25 |
| 5 | 5.683 | 5.532 | 0.258 | 7.31 | 0.44 | 8.00 | 40 | 12.00 |
| 6 | 6.743 | 6.594 | 0.280 | 8.50 | 0.50 | 8.00 | 40 | 16.00 |
| 8 | 8.743 | 8.594 | 0.322 | 10.62 | 0.50 | 8.00 | 40 | 23.00 |
| 10 | 10.913 | 10.719 | 0.365 | 12.75 | 0.50 | 10.00 | 40 | 36.00 |
| 12 | 12.913 | 12.719 | 0.406 | 15.00 | 0.50 | 10.00 | 40 | 52.00 |
| 14 | 14.170 | 13.969 | 0.438 | 16.25 | 0.50 | 12.00 | 40 | 73.00 |
| 16 | 16.180 | 15.969 | 0.500 | 18.50 | 0.50 | 12.00 | 40 | 97.00 |
| 18 | 18.190 | 17.969 | 0.562 | 21.00 | 0.50 | 12.00 | 40 | 126.00 |
| 20 | 20.240 | 19.969 | 0.594 | 23.00 | 0.50 | 12.00 | 40 | 147.00 |
| 24 | 24.240 | 23.969 | 0.688 | 27.25 | 0.50 | 12.00 | 40 | 205.00 |
Schedule 80
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.147 | 1.38 | 0.12 | 3.00 | 80 | 0.38 |
| ¾ | 1.106 | 1.019 | 0.154 | 1.69 | 0.12 | 3.00 | 80 | 0.51 |
| 1 | 1.376 | 1.284 | 0.179 | 2.00 | 0.12 | 4.00 | 80 | 1.00 |
| 1¼ | 1.716 | 1.629 | 0.191 | 2.50 | 0.19 | 4.00 | 80 | 1.25 |
| 1½ | 1.965 | 1.869 | 0.200 | 2.88 | 0.25 | 4.00 | 80 | 1.75 |
| 2 | 2.456 | 2.344 | 0.218 | 3.62 | 0.31 | 6.00 | 80 | 3.00 |
| 2½ | 2.966 | 2.844 | 0.276 | 4.12 | 0.31 | 6.00 | 80 | 4.50 |
| 3 | 3.596 | 3.469 | 0.300 | 5.00 | 0.38 | 6.00 | 80 | 6.50 |
| 3½ | 4.096 | 3.969 | 0.318 | 5.50 | 0.38 | 6.00 | 80 | 7.75 |
| 4 | 4.593 | 4.469 | 0.337 | 6.19 | 0.44 | 6.00 | 80 | 9.50 |
| 5 | 5.683 | 5.532 | 0.375 | 7.31 | 0.44 | 8.00 | 80 | 17.00 |
| 6 | 6.743 | 6.594 | 0.432 | 8.50 | 0.50 | 8.00 | 80 | 23.00 |
| 8 | 8.743 | 8.594 | 0.500 | 10.62 | 0.50 | 8.00 | 80 | 32.00 |
| 10 | 10.913 | 10.719 | 0.594 | 12.75 | 0.50 | 10.00 | 80 | 63.00 |
| 12 | 12.913 | 12.719 | 0.688 | 15.00 | 0.50 | 10.00 | 80 | 87.00 |
| 14 | 14.170 | 13.969 | 0.750 | 16.25 | 0.50 | 12.00 | 80 | 123.00 |
| 16 | 16.180 | 15.969 | 0.844 | 18.50 | 0.50 | 12.00 | 80 | 161.00 |
| 18 | 18.190 | 17.969 | 0.938 | 21.00 | 0.50 | 12.00 | 80 | 205.00 |
| 20 | 20.240 | 19.969 | 1.031 | 23.00 | 0.50 | 12.00 | 80 | 251.00 |
| 24 | 24.240 | 23.969 | 1.219 | 27.25 | 0.50 | 12.00 | 80 | 359.00 |
Schedule 160
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.188 | 1.38 | 0.12 | 3.00 | 160 | 0.75 |
| ¾ | 1.106 | 1.019 | 0.219 | 1.69 | 0.12 | 3.00 | 160 | 0.95 |
| 1 | 1.376 | 1.284 | 0.250 | 2.00 | 0.12 | 4.00 | 160 | 1.13 |
| 1¼ | 1.716 | 1.629 | 0.250 | 2.50 | 0.19 | 4.00 | 160 | 1.51 |
| 1½ | 1.965 | 1.869 | 0.281 | 2.88 | 0.25 | 4.00 | 160 | 2.02 |
| 2 | 2.456 | 2.344 | 0.344 | 3.62 | 0.31 | 6.00 | 160 | 4.51 |
| 2½ | 2.966 | 2.844 | 0.375 | 4.12 | 0.31 | 6.00 | 160 | 6.02 |
| 3 | 3.596 | 3.469 | 0.438 | 5.00 | 0.38 | 6.00 | 160 | 8.80 |
| 4 | 4.593 | 4.469 | 0.531 | 6.19 | 0.44 | 6.00 | 160 | 14.10 |
| 5 | 5.683 | 5.532 | 0.625 | 7.31 | 0.44 | 8.00 | 160 | 26.40 |
| 6 | 6.743 | 6.594 | 0.719 | 8.50 | 0.50 | 8.00 | 160 | 36.40 |
| 8 | 8.743 | 8.594 | 0.906 | 10.62 | 0.50 | 8.00 | 160 | 60.00 |
| 10 | 10.913 | 10.719 | 1.125 | 12.75 | 0.50 | 10.00 | 160 | 113.00 |
| 12 | 12.913 | 12.719 | 1.312 | 15.00 | 0.50 | 10.00 | 160 | 160.00 |
| 14 | 14.170 | 13.969 | 1.406 | 16.25 | 0.50 | 12.00 | 160 | 190.00 |
| 16 | 16.180 | 15.969 | 1.594 | 18.50 | 0.50 | 12.00 | 160 | 245.00 |
| 18 | 18.190 | 17.969 | 1.781 | 21.00 | 0.50 | 12.00 | 160 | 309.00 |
| 20 | 20.240 | 19.969 | 1.969 | 23.00 | 0.50 | 12.00 | 160 | 379.00 |
| 24 | 24.240 | 23.969 | 2.344 | 27.25 | 0.50 | 12.00 | 160 | 542.00 |
Schedule XXS
| Nom. Pipe Size | Outside Dia. (Max.) | Outside Dia. (Min.) | Wall & Lap Thickness T | Lap Diameter K | Fillet Radius N | Overall Length (Long) J | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|---|---|
| ½ | 0.896 | 0.809 | 0.294 | 1.38 | 0.12 | 3.00 | * | 1.75 |
| ¾ | 1.106 | 1.019 | 0.308 | 1.69 | 0.12 | 3.00 | * | 2.50 |
| 1 | 1.376 | 1.284 | 0.358 | 2.00 | 0.12 | 4.00 | * | 4.00 |
| 1¼ | 1.716 | 1.629 | 0.382 | 2.50 | 0.19 | 4.00 | * | 6.25 |
| 1½ | 1.965 | 1.869 | 0.400 | 2.88 | 0.25 | 4.00 | * | 6.50 |
| 2 | 2.456 | 2.344 | 0.436 | 3.62 | 0.31 | 6.00 | * | 9.00 |
| 2½ | 2.966 | 2.844 | 0.552 | 4.12 | 0.31 | 6.00 | * | 14.00 |
| 3 | 3.596 | 3.469 | 0.600 | 5.00 | 0.38 | 6.00 | * | 18.50 |
| 4 | 4.593 | 4.469 | 0.674 | 6.19 | 0.44 | 6.00 | * | 27.50 |
| 5 | 5.683 | 5.532 | 0.750 | 7.31 | 0.44 | 8.00 | * | 39.00 |
| 6 | 6.743 | 6.594 | 0.864 | 8.50 | 0.50 | 8.00 | * | 54.00 |
| 8 | 8.743 | 8.594 | 0.875 | 10.62 | 0.50 | 8.00 | * | 73.00 |
| 10 | 10.913 | 10.719 | 1.000 | 12.75 | 0.50 | 10.00 | 140 | 116.00 |
| 12 | 12.913 | 12.719 | 1.000 | 15.00 | 0.50 | 10.00 | 120 | 167.00 |
Materials We Supply
Lap Joint Stub End to MSS SP-43 Type A in the grades below. Tell us the service and we'll confirm the right one for y'all.
| Material | Specification | Typical Service |
|---|---|---|
| Carbon Steel | ASTM A234 WPB / WPC | General process, steam, oil and gas gathering and utility lines |
| Low-Temp Carbon Steel | ASTM A420 WPL6 | Cold service to −50°F; LNG and northern pipeline work |
| Chrome-Moly Alloy | ASTM A234 WP11 / WP22 / WP91 | Elevated temperature; refinery heaters, power plant steam |
| Stainless Steel | ASTM A403 WP304/304L, WP316/316L | Corrosive service, chemical, food and beverage, water treatment |
| Duplex & Super Duplex | ASTM A815 UNS S31803 / S32750 | Chloride and seawater service, offshore, desalination |
Questions Folks Ask Us
What's a lap joint stub end?
Dat's a short butt weld fitting with a lapped face. It welds right to the pipe and makes up the sealin' face, while a separate lap joint backing flange slides on behind the lap and carries the bolting on through to the mating flange. The flange bears down on the back of the lap instead of hookin' to the stub end. Only dat stub end ever touches your process fluid, I tell you what.
Why use a stub end and backin' flange 'stead of a weld neck flange?
Cost and alignment. Dat backing flange never touches the fluid, so it can be carbon steel behind a stainless or alloy stub end. It also rotates freely, so bolt holes line up on site without turnin' the pipe.
What's the difference 'tween long and short pattern stub ends?
Overall length J, and the standard that defines it. Dem tables above are MSS SP-43 Type A, the long pattern, dimensioned to follow ASME B16.9. Type B is the short pattern and Type C is a reducin' pattern, both of 'em shorter. Y'all better confirm which type dat spool was drawn around before orderin', 'cause they ain't interchangeable in a fixed spool, no sir.
