Butt Weld Cap Dimensions
A cap closes up the end of a pipe run with a single butt weld. The standard profile is 2:1 ellipsoidal, which holds pressure a whole lot better than a flat closure, and dat's why a welded cap is the normal way to terminate a line permanently, yessir.
Why the domed profile.
A flat plate closin' a pressurised pipe carries bendin' stress across its whole face. Dat ellipsoidal head turns dat into membrane stress in a curved shell, so the cap can hold full line pressure at roughly the same wall thickness as the pipe it closes, I tell you what.
Cap or blind flange.
A cap is your answer when the end is meant to stay closed up: line terminations, future tie-in stubs, and dead legs. But when dat end has to be opened for cleanin', inspection, or a future connection, a blind flange on a weld neck is the right call, 'cause openin' a welded cap means you gotta cut it right out.
How To Read Dese Dimensions
ASME B16.9 dimensions the buttweld cap, includin' the 2:1 ellipsoidal profile that lets it hold line pressure at roughly pipe wall thickness. The overall height H down below is the standard figure.
- O.D.
- Outside diameterOutside diameter at the weldin' end, matchin' up perfect with the pipe it welds to.
- I.D.
- Inside diameterBore right through the fitting, set by dat wall thickness.
- T
- Wall thicknessNominal wall at the weldin' end, matched to the pipe schedule.
- H
- Overall heightFrom the welding face to the top of the dome.
121 sizes across 6 schedules · dimensions in inches, weights in pounds · ASME B16.9
Schedule STD
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.622 | 0.109 | 1.00 | 40 | 0.08 |
| ¾ | 1.05 | 0.824 | 0.113 | 1.00 | 40 | 0.14 |
| 1 | 1.32 | 1.049 | 0.133 | 1.50 | 40 | 0.21 |
| 1¼ | 1.66 | 1.380 | 0.140 | 1.50 | 40 | 0.33 |
| 1½ | 1.90 | 1.610 | 0.145 | 1.50 | 40 | 0.54 |
| 2 | 2.38 | 2.067 | 0.154 | 1.50 | 40 | 0.80 |
| 2½ | 2.88 | 2.469 | 0.203 | 1.50 | 40 | 1.00 |
| 3 | 3.50 | 3.068 | 0.216 | 2.00 | 40 | 1.70 |
| 3½ | 4.00 | 3.548 | 0.226 | 2.50 | 40 | 2.30 |
| 4 | 4.50 | 4.026 | 0.237 | 2.50 | 40 | 2.80 |
| 5 | 5.56 | 5.047 | 0.258 | 3.00 | 40 | 4.60 |
| 6 | 6.62 | 6.065 | 0.280 | 3.50 | 40 | 6.90 |
| 8 | 8.62 | 7.981 | 0.322 | 4.00 | 40 | 11.80 |
| 10 | 10.75 | 10.020 | 0.365 | 5.00 | 40 | 20.80 |
| 12 | 12.75 | 12.000 | 0.375 | 6.00 | * | 30.30 |
| 14 | 14.00 | 13.250 | 0.375 | 6.50 | 30 | 36.50 |
| 16 | 16.00 | 15.250 | 0.375 | 7.00 | 30 | 43.50 |
| 18 | 18.00 | 17.250 | 0.375 | 8.00 | * | 57.00 |
| 20 | 20.00 | 19.250 | 0.375 | 9.00 | 20 | 75.70 |
| 24 | 24.00 | 23.250 | 0.375 | 10.50 | 20 | 101.00 |
| 30 | 30.00 | 29.250 | 0.375 | 10.50 | * | 137.00 |
| 36 | 36.00 | 35.250 | 0.375 | 10.50 | * | 175.00 |
| 42 | 42.00 | 41.250 | 0.375 | 12.00 | * | 229.00 |
| 48 | 48.00 | 47.250 | 0.375 | 13.50 | * | 350.00 |
Schedule XS
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.546 | 0.147 | 1.00 | 80 | 0.10 |
| ¾ | 1.05 | 0.742 | 0.154 | 1.00 | 80 | 0.16 |
| 1 | 1.32 | 0.957 | 0.179 | 1.50 | 80 | 0.28 |
| 1¼ | 1.66 | 1.278 | 0.191 | 1.50 | 80 | 0.48 |
| 1½ | 1.90 | 1.500 | 0.200 | 1.50 | 80 | 0.67 |
| 2 | 2.38 | 1.939 | 0.218 | 1.50 | 80 | 0.92 |
| 2½ | 2.88 | 2.323 | 0.276 | 1.50 | 80 | 1.30 |
| 3 | 3.50 | 2.900 | 0.300 | 2.00 | 80 | 2.10 |
| 3½ | 4.00 | 3.364 | 0.318 | 2.50 | 80 | 3.00 |
| 4 | 4.50 | 3.826 | 0.337 | 2.50 | 80 | 3.50 |
| 5 | 5.56 | 4.813 | 0.375 | 3.00 | 80 | 5.80 |
| 6 | 6.62 | 5.761 | 0.432 | 3.50 | 80 | 9.30 |
| 8 | 8.62 | 7.625 | 0.500 | 4.00 | 80 | 16.00 |
| 10 | 10.75 | 9.750 | 0.500 | 5.00 | 60 | 26.00 |
| 12 | 12.75 | 11.750 | 0.500 | 6.00 | * | 38.00 |
| 14 | 14.00 | 13.000 | 0.500 | 6.50 | * | 47.00 |
| 16 | 16.00 | 15.000 | 0.500 | 7.00 | 40 | 57.00 |
| 18 | 18.00 | 17.000 | 0.500 | 8.00 | * | 78.00 |
| 20 | 20.00 | 19.000 | 0.500 | 9.00 | 30 | 100.00 |
| 24 | 24.00 | 23.000 | 0.500 | 10.50 | * | 145.00 |
| 30 | 30.00 | 29.000 | 0.500 | 10.50 | 20 | 634.00 |
| 36 | 36.00 | 35.000 | 0.500 | 10.50 | 20 | 913.00 |
| 42 | 42.00 | 41.000 | 0.500 | 12.00 | * | 1300.00 |
| 48 | 48.00 | 47.000 | 0.500 | 13.50 | * | 1675.00 |
Schedule 40
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.622 | 0.109 | 1.00 | 40 | 0.08 |
| ¾ | 1.05 | 0.824 | 0.113 | 1.00 | 40 | 0.14 |
| 1 | 1.32 | 1.054 | 0.133 | 1.50 | 40 | 0.21 |
| 1¼ | 1.66 | 1.380 | 0.140 | 1.50 | 40 | 0.33 |
| 1½ | 1.90 | 1.610 | 0.145 | 1.50 | 40 | 0.54 |
| 2 | 2.38 | 2.072 | 0.154 | 1.50 | 40 | 0.80 |
| 2½ | 2.88 | 2.474 | 0.203 | 1.50 | 40 | 1.00 |
| 3 | 3.50 | 3.068 | 0.216 | 2.00 | 40 | 1.70 |
| 3½ | 4.00 | 3.548 | 0.226 | 2.50 | 40 | 2.30 |
| 4 | 4.50 | 4.026 | 0.237 | 2.50 | 40 | 2.80 |
| 5 | 5.56 | 5.044 | 0.258 | 3.00 | 40 | 4.60 |
| 6 | 6.62 | 6.060 | 0.280 | 3.50 | 40 | 6.90 |
| 8 | 8.62 | 7.976 | 0.322 | 4.00 | 40 | 11.80 |
| 10 | 10.75 | 10.020 | 0.365 | 5.00 | 40 | 20.80 |
| 12 | 12.75 | 11.938 | 0.406 | 6.00 | 40 | 30.30 |
| 14 | 14.00 | 13.124 | 0.438 | 6.50 | 40 | 36.50 |
| 16 | 16.00 | 15.000 | 0.500 | 7.00 | 40 | 43.50 |
| 18 | 18.00 | 16.876 | 0.562 | 9.00 | 40 | 57.00 |
| 20 | 20.00 | 18.812 | 0.594 | 10.00 | 40 | 75.70 |
| 24 | 24.00 | 22.624 | 0.688 | 12.00 | 40 | 101.00 |
Schedule 80
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.546 | 0.147 | 1.00 | 80 | 0.10 |
| ¾ | 1.05 | 0.742 | 0.154 | 1.00 | 80 | 0.16 |
| 1 | 1.32 | 0.962 | 0.179 | 1.50 | 80 | 0.28 |
| 1¼ | 1.66 | 1.278 | 0.191 | 1.50 | 80 | 0.48 |
| 1½ | 1.90 | 1.500 | 0.200 | 1.50 | 80 | 0.67 |
| 2 | 2.38 | 1.944 | 0.218 | 1.50 | 80 | 0.92 |
| 2½ | 2.88 | 2.328 | 0.276 | 1.50 | 80 | 1.30 |
| 3 | 3.50 | 2.900 | 0.300 | 2.00 | 80 | 2.10 |
| 3½ | 4.00 | 3.364 | 0.318 | 2.50 | 80 | 3.00 |
| 4 | 4.50 | 3.826 | 0.337 | 2.50 | 80 | 3.50 |
| 5 | 5.56 | 4.810 | 0.375 | 3.00 | 80 | 5.80 |
| 6 | 6.62 | 5.756 | 0.432 | 3.50 | 80 | 9.30 |
| 8 | 8.62 | 7.620 | 0.500 | 4.00 | 80 | 16.00 |
| 10 | 10.75 | 9.562 | 0.594 | 6.00 | 80 | 26.00 |
| 12 | 12.75 | 11.374 | 0.688 | 7.00 | 80 | 38.00 |
| 14 | 14.00 | 12.500 | 0.750 | 7.50 | 80 | 47.00 |
| 16 | 16.00 | 14.312 | 0.844 | 8.00 | 80 | 57.00 |
| 18 | 18.00 | 16.124 | 0.938 | 9.00 | 80 | 78.00 |
| 20 | 20.00 | 17.938 | 1.031 | 10.00 | 80 | 100.00 |
| 24 | 24.00 | 21.562 | 1.219 | 12.00 | 80 | 145.00 |
Schedule 160
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.464 | 0.188 | 1.00 | 160 | 0.30 |
| ¾ | 1.05 | 0.612 | 0.219 | 1.00 | 160 | 0.30 |
| 1 | 1.32 | 0.820 | 0.250 | 1.50 | 160 | 0.40 |
| 1¼ | 1.66 | 1.160 | 0.250 | 1.50 | 160 | 0.50 |
| 1½ | 1.90 | 1.338 | 0.281 | 1.50 | 160 | 0.60 |
| 2 | 2.38 | 1.692 | 0.344 | 1.75 | 160 | 1.30 |
| 2½ | 2.88 | 2.130 | 0.375 | 2.00 | 160 | 1.80 |
| 3 | 3.50 | 2.624 | 0.438 | 2.50 | 160 | 2.90 |
| 4 | 4.50 | 3.438 | 0.531 | 3.00 | 160 | 5.90 |
| 5 | 5.56 | 4.310 | 0.625 | 3.50 | 160 | 10.00 |
| 6 | 6.62 | 5.182 | 0.719 | 4.00 | 160 | 15.00 |
| 8 | 8.62 | 6.808 | 0.906 | 5.00 | 160 | 31.00 |
| 10 | 10.75 | 8.500 | 1.125 | 6.00 | 160 | 57.00 |
| 12 | 12.75 | 10.126 | 1.312 | 7.00 | 160 | 95.00 |
| 14 | 14.00 | 11.188 | 1.406 | 7.50 | 160 | 200.00 |
| 16 | 16.00 | 12.812 | 1.594 | 8.00 | 160 | 297.00 |
| 18 | 18.00 | 14.438 | 1.781 | 9.00 | 160 | 360.00 |
| 20 | 20.00 | 16.062 | 1.969 | 10.00 | 160 | 420.00 |
| 24 | 24.00 | 19.312 | 2.344 | 12.00 | 160 | 535.00 |
Schedule XXS
| Nom. Pipe Size | Outside Diameter O.D. | Inside Diameter I.D. | Wall Thickness T | Height H | Pipe Schedule Number | Approx. Weight in Pounds Lbs. |
|---|---|---|---|---|---|---|
| ½ | 0.84 | 0.252 | 0.294 | 1.00 | * | 0.50 |
| ¾ | 1.05 | 0.434 | 0.308 | 1.00 | * | 0.75 |
| 1 | 1.32 | 0.604 | 0.358 | 1.50 | * | 1.00 |
| 1¼ | 1.66 | 0.896 | 0.382 | 1.50 | * | 1.50 |
| 1½ | 1.90 | 1.100 | 0.400 | 1.50 | * | 2.50 |
| 2 | 2.38 | 1.508 | 0.436 | 1.75 | * | 3.00 |
| 2½ | 2.88 | 1.776 | 0.552 | 2.00 | * | 4.00 |
| 3 | 3.50 | 2.300 | 0.600 | 2.50 | * | 6.00 |
| 4 | 4.50 | 3.152 | 0.674 | 3.00 | * | 9.00 |
| 5 | 5.56 | 4.060 | 0.750 | 3.50 | * | 13.50 |
| 6 | 6.62 | 4.892 | 0.864 | 4.00 | * | 18.00 |
| 8 | 8.62 | 6.870 | 0.875 | 5.00 | * | 26.00 |
| 10 | 10.75 | 8.750 | 1.000 | 6.00 | 140 | 46.00 |
| 12 | 12.75 | 10.750 | 1.000 | 7.00 | 120 | 68.00 |
Materials We Supply
Cap to ASME B16.9 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 butt weld cap used for?
For permanently closin' up the end of a pipe. It butt welds to the pipe with a single circumferential weld and, with dat 2:1 ellipsoidal profile, it holds the full pressure rating of the line without breakin' a sweat.
Should I use a cap or a blind flange?
A cap is for when the closure is permanent. It's cheaper, lighter, and ain't got no gasket or bolts to mess with. A blind flange is for when the end gotta be opened again for cleanin', inspection, or a future connection, since takin' off a welded cap means you're fixin' to cut it off.
What's dat H dimension on a cap?
H is the overall height of the cap, measured from the welding end face to the top of the dome. It's listed for every size and schedule right up there in dem tables.
