Caps look simple and are not. A butt weld cap is a dished head — the common profile is ellipsoidal — and it carries end pressure the way a vessel head does, which is why its crown depth and minimum wall are standardised rather than left to the maker. A cap is welded on where a line ends permanently, or where a future extension is planned but the line must be pressure-tight and testable now.
Order a cap exactly as you would the pipe it closes: nominal size, schedule (which sets the skirt wall and bevel), and grade. Where the cap closes a large line and will see full hydrotest pressure, say so — wall selection follows the same logic as the pipe.
| Item | Range / Options |
|---|---|
| Types | Butt weld end caps |
| Standards | Confirmed per product at enquiry |
| Size range | Confirmed per product at enquiry — state the size and wall of the line the cap closes |
| Wall thickness | Confirmed per product at enquiry — state the schedule of the connecting pipe on the enquiry |
| Materials | Carbon and stainless executions are listed in the catalogue; the grade is confirmed per product at enquiry |
| Surface | Surface finish confirmed per product at enquiry |
Cap, Blind Flange or Plug?
Three ways to close a line end, three different logics. A welded cap is permanent and needs no bolting or gasket — cheapest and lightest, but cutting it off is the only way back in. A blind flange closes a flanged end and can be unbolted for access. A forged plug closes a small threaded or socket weld outlet. Most line ends that will never open get caps; most equipment nozzles get blinds.
Forming and Finishing
Caps are pressed from plate or pipe and trimmed; the crown depth and skirt length follow the standard's dimensions for the size. The skirt wall and bevel for a specific cap are confirmed against the schedule of the pipe it closes before order. Surface finish and packing for caps are agreed at quotation — state any finish requirement, and any protection the bevel edge needs in transit, on the enquiry.
On the Same Order
Caps are usually the last line on a fitting list, ordered with the elbows, tees and reducers of the same line. Put them on one consolidated list with the enquiry: each item's grade and schedule is assessed and confirmed for the specific product before order, and the list is quoted and packed as one package.
Frequently Asked Questions
Is a butt weld cap pressure rated like the pipe?
A butt weld cap is designed to be used with pipe of the corresponding schedule; its dished profile and minimum wall follow the fitting standard so the cap is not the weak point of the line. Keep the cap schedule equal to the pipe schedule.
Can caps be supplied in large diameters?
Larger caps are formed from plate and welded rather than pressed from seamless pipe. State the size and wall on your enquiry and the construction will be confirmed for that product.
Do you also make threaded and socket weld caps?
Small-bore caps belong to the forged fittings family — see the forged fittings page for the range; the execution for a specific cap is confirmed per product at enquiry.
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Send Your Specification
Tell us the size, schedule or pressure class, material grade and quantity for the butt weld caps you need. MOQ and lead time are confirmed in the quotation for your exact specification.