# Butt-weld caps (ASME B16.9), NPS 1/2 to 12: overall length E and E1 by wall thickness

> How long is a butt-weld pipe cap (length E) for Schedule 40 and 80?

- Category: Tri-clamp & pipe › Pipe, tube & threads
- Kind: Standard part
- Basis: Length E / E1 (mm) and the wall that separates them from Wermac's ASME B16.9 cap table; Schedule 40 and 80 heights H (in) and walls T from Texas Flange; numbers only
- Page: https://xemstudio.com/objects/butt-weld-caps/ · JSON: https://xemstudio.com/api/geometry?object=butt-weld-caps · Plain text: https://xemstudio.com/objects/butt-weld-caps/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
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**Exact dimensions.** True size, with no tolerance added.

## Notes

- B16.9 gives each cap size two lengths: E for walls up to a limit and E1 for thicker walls. Wermac prints both and the limiting wall (column 'wall limit'): E applies when the fitting wall is not more than the limit, E1 when it is more. Texas Flange's per-schedule heights H (weld face to the top of the dome) agree with this rule: for NPS 10 Sch 40 (wall 0.365 in, under the 12.7 mm limit) H = 5.00 in = E 127 mm; for NPS 10 Sch 80 (wall 0.594 in, over the limit) H = 6.00 in = E1 152 mm. Sch 80 at NPS 2 (wall 0.218 in = 5.54 mm, under the 5.59 mm limit) is still the short E (1.50 in = 38 mm). One boundary case disagrees: NPS 6 Sch 80 has a 0.432 in (10.97 mm) wall, 0.05 mm over Wermac's 10.92 mm limit, so the rule gives E1 = 102 mm while Texas Flange prints H = 3.50 in (89 mm, the short E); both are shown and neither is resolved here.
- Wermac lists the limit as 12.70 mm from NPS 8 up through NPS 24; above NPS 24 it prints no E1 (by agreement between maker and buyer), and this page stops at NPS 12.
- Where inch and mm disagree it is rounding: Texas Flange's 1.50 in at NPS 1 is Wermac's 38 mm (1.496 in).
- No file: E, OD and wall define the length, the weld end and the wall, but not the crown. Where the straight part ends and the dome (and its knuckle radius) begin is not given as numbers in any source read, so a drawn dome would be an invention. McMaster-Carr sells butt-weld end caps with per-part STEP; its category is linked, not copied.
- OD: Wermac prints mm (21.3 ... 323.8), Texas Flange inches as printed (0.84 ... 12.75); both are rounded figures.

## Sizes

| NPS | OD, mm (in) | E, mm | E1, mm | wall limit between E and E1, mm | Sch 40 height H, in (Texas Flange) | Sch 80 height H, in (Texas Flange) |
|---|---|---|---|---|---|---|
| 1/2 | 21.3 (0.84 in) | 25 | 25 | 4.57 | 1.00 (wall 0.109) | 1.00 (wall 0.147) |
| 3/4 | 26.7 (1.05 in) | 25 | 25 | 3.81 | 1.00 (wall 0.113) | 1.00 (wall 0.154) |
| 1 | 33.4 (1.32 in) | 38 | 38 | 4.57 | 1.50 (wall 0.133) | 1.50 (wall 0.179) |
| 1-1/4 | 42.2 (1.66 in) | 38 | 38 | 4.83 | 1.50 (wall 0.140) | 1.50 (wall 0.191) |
| 1-1/2 | 48.3 (1.90 in) | 38 | 38 | 5.08 | 1.50 (wall 0.145) | 1.50 (wall 0.200) |
| 2 | 60.3 (2.38 in) | 38 | 44 | 5.59 | 1.50 (wall 0.154) | 1.50 (wall 0.218) |
| 2-1/2 | 73.0 (2.88 in) | 38 | 51 | 7.11 | 1.50 (wall 0.203) | 1.50 (wall 0.276) |
| 3 | 88.9 (3.50 in) | 51 | 64 | 7.62 | 2.00 (wall 0.216) | 2.00 (wall 0.300) |
| 3-1/2 | 101.6 (4.00 in) | 64 | 76 | 8.13 | 2.50 (wall 0.226) | 2.50 (wall 0.318) |
| 4 | 114.3 (4.50 in) | 64 | 76 | 8.64 | 2.50 (wall 0.237) | 2.50 (wall 0.337) |
| 5 | 141.3 (5.56 in) | 76 | 89 | 9.65 | 3.00 (wall 0.258) | 3.00 (wall 0.375) |
| 6 | 168.3 (6.62 in) | 89 | 102 | 10.92 | 3.50 (wall 0.280) | 3.50 (wall 0.432) |
| 8 | 219.1 (8.62 in) | 102 | 127 | 12.70 | 4.00 (wall 0.322) | 4.00 (wall 0.500) |
| 10 | 273.0 (10.75 in) | 127 | 152 | 12.70 | 5.00 (wall 0.365) | 6.00 (wall 0.594) |
| 12 | 323.8 (12.75 in) | 152 | 178 | 12.70 | 6.00 (wall 0.406) | 7.00 (wall 0.688) |

## Where the files are

- Wermac: [ASME B16.9 butt-weld cap dimensions: E, E1 and the wall that separates them (mm)](https://wermac.org/fittings/dim_caps.html) — web — Publisher's page; dimensions are facts
- Texas Flange (manufacturer / distributor): [Butt-weld caps: OD, ID, wall T and height H for STD, XS, Sch 40, 80, 160, XXS](https://texasflange.com/butt-weld-fittings/cap/) — web — Publisher's page; dimensions are facts
- McMaster-Carr: [Butt-weld end caps (free STEP/IGES per part, for your own design use; no redistribution)](https://www.mcmaster.com/products/end-caps/fitting-connection~butt-weld/) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution (verify at link)

## Questions

**How long is a 2 inch Schedule 40 butt-weld cap?**

E = 38 mm (1.50 in) for Sch 40 and Sch 80 (walls under the 5.59 mm limit); a thicker wall (over 5.59 mm) uses E1 = 44 mm.

**What is E1 on a weld cap?**

The longer length used when the fitting wall is thicker than the size's limit (for example over 12.7 mm from NPS 8 up).

## Fits with

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- [Butt-weld reducers, concentric and eccentric (ASME B16.9), NPS ¾ to 12](https://xemstudio.com/objects/butt-weld-reducers/)
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