Butt Weld Cap Dimensions
A cap closes the end of a pipe run with a single butt weld. The standard profile is 2:1 ellipsoidal, which carries pressure far better than a flat closure, and is why a welded cap is the normal way to terminate a line permanently.
Why the domed profile.
A flat plate closing a pressurised pipe carries bending stress across its whole face. The ellipsoidal head turns that 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.
Cap or blind flange.
A cap is the answer when the end is meant to stay closed: line terminations, future tie-in stubs, and dead legs. When the end has to be opened for cleaning, inspection, or a future connection, a blind flange on a weld neck is the right call, because opening a welded cap means cutting it out.
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 will confirm the right one.
| 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 |
Common Questions
What is a butt weld cap used for?
Permanently closing the end of a pipe. It butt welds to the pipe with a single circumferential weld and, with its 2:1 ellipsoidal profile, holds the full pressure rating of the line.
Should I use a cap or a blind flange?
A cap where the closure is permanent. It is cheaper, lighter, and has no gasket or bolts to maintain. A blind flange where the end has to be opened again for cleaning, inspection, or a future connection, since removing a welded cap means cutting it off.
What is the 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 is listed for every size and schedule in the tables above.
