ASME B16.9 Table 10 provides dimensions for buttweld caps for size ranges ½” to 48”. Caps are mostly used to close the pipe ends on pipe racks when there is no future expansion of pipe is planned. They are also used at the bottom of condensate drip legs where a hole is drilled on cap head and a drain connection is added. There are also useful in installing drain and vent at the top and bottom of level instruments standpipe on process equipments. This page provides metric dimensions for buttweld caps.
Available Dimensions are: OD | Outside Diameter at Bevel, E | Cap Length, T | Limiting wall thickness for length E, E1 | Cap Length.
| NPS | OD | E | T | E1 |
|---|---|---|---|---|
| 1/2 | 21.3 | 25 | 4.57 | 25 |
| 3/4 | 26.7 | 25 | 3.81 | 25 |
| 1 | 33.4 | 38 | 4.57 | 38 |
| 1-1/4 | 42.2 | 38 | 4.83 | 38 |
| 1-1/2 | 48.3 | 38 | 5.08 | 38 |
| 2 | 60.3 | 38 | 5.59 | 44 |
| 2-1/2 | 73.0 | 38 | 7.11 | 51 |
| 3 | 88.9 | 51 | 7.62 | 64 |
| 3-1/2 | 101.6 | 64 | 8.13 | 76 |
| 4 | 114.3 | 64 | 8.64 | 76 |
| 5 | 141.3 | 76 | 9.65 | 89 |
| 6 | 168.3 | 89 | 10.9 | 102 |
| 8 | 219.1 | 102 | 12.7 | 127 |
| 10 | 273.0 | 127 | 12.7 | 152 |
| 12 | 323.8 | 152 | 12.7 | 178 |
| 14 | 355.6 | 165 | 12.7 | 191 |
| 16 | 406.4 | 178 | 12.7 | 203 |
| 18 | 457.0 | 203 | 12.7 | 229 |
| 20 | 508.0 | 229 | 12.7 | 254 |
| 22 | 559.0 | 254 | 12.7 | 254 |
| 24 | 610.0 | 267 | 12.7 | 305 |
| 26 | 660.0 | 267 | NA | NA |
| 28 | 711.0 | 267 | NA | NA |
| 30 | 762.0 | 267 | NA | NA |
| 32 | 813.0 | 267 | NA | NA |
| 34 | 864.0 | 267 | NA | NA |
| 36 | 914.0 | 267 | NA | NA |
| 38 | 965.0 | 305 | NA | NA |
| 40 | 1016.0 | 305 | NA | NA |
| 42 | 1067.0 | 305 | NA | NA |
| 44 | 1118.0 | 343 | NA | NA |
| 46 | 1168.0 | 343 | NA | NA |
| 48 | 1219.0 | 343 | NA | NA |
GENERAL NOTES:
(a) All dimensions are in millimeters.
(b) The shape of these caps shall be ellipsoidal and shall conform to the shape requirements as given in the ASME Boiler and Pressure Vessel Code.
NOTES:
(1) Length E applies for thickness not exceeding that given in column “Limiting Wall Thickness for Length, E.”
(2) Length E1 applies for thickness greater than that given in column “Limiting Wall Thickness” for NPS 24 and smaller. For NPS 26 and larger, length E1 shall be by agreement between the manufacturer and purchaser.
