SS 904L CapASTM A403 · ASME B16.9 · Manufacturer, trader & exporter, India
Alloy 904L · UNS N08904
An SS 904L cap is a fitting that closes the end of a pipe, made from SS 904L to ASTM A403 WP904L (buttweld) · ASTM A182 F904L (forged). Buttweld caps are dished ends welded to the pipe; forged caps are threaded or socket-weld. Used at dead ends and future connection points.
For the full 904L fittings range, see SS 904L pipe fittings.
- ASTM A403
- ASME B16.9
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 904L Cap?
- What it is
- A fitting that closes the end of a pipe
- Material
- ASTM A403 WP904L (buttweld) · ASTM A182 F904L (forged)
- Dimensions
- ASME B16.9 · B16.11
- Grade
- SS 904L · UNS N08904
- Best at
- Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water
SS 904L Cap Specification
| Product | SS 904L Cap |
|---|---|
| Material standard | ASTM A403 WP904L (buttweld) · ASTM A182 F904L (forged) |
| Dimensional standard | ASME B16.9 · B16.11 |
| Sizes | Buttweld ½" – 48" · forged ⅛" – 4" |
| Wall / class | Schedule to match pipe · Class 3000 / 6000 (forged) |
| Ends | Bevelled to ASME B16.25 |
| Testing | PMI (as specified in the PO) · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 or 3.2 on request / as specified in the PO |
When to Choose a Cap
Buttweld caps are dished ends welded to the pipe; forged caps are threaded or socket-weld. Used at dead ends and future connection points.
- Buttweld dished caps
- Threaded and socket-weld caps
- Wall to match the pipe
More on choosing: Cap guide.
SS 904L Cap: Why 904L for caps
Buttweld caps are dished ends welded to the pipe; forged caps are threaded or socket-weld. Used at dead ends and future connection points. In SS 904L, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless fittings keep the line clean and corrosion-free. SS 904L is picked for dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water. |
|---|---|
| Typical service | Sulphuric acid plants — Coolers, piping and tanks for dilute sulphuric acid. |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER385 (AWS A5.9) |
SS 904L Cap Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Nickel | As specified |
| Chromium | As specified |
| Molybdenum | As specified |
| Copper | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Nitrogen | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS N08904.
SS 904L Cap Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS N08904 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 904L grade page.
Other SS 904L pipe fittings
SS 904L Cap dimensions — ASME B16.9
Values in mm, the same for every material; the wall thickness matches the pipe schedule.
| NPS | OD | Cap length E |
|---|---|---|
| ½" | 21.3 | 25 |
| ¾" | 26.7 | 25 |
| 1" | 33.4 | 38 |
| 1½" | 48.3 | 38 |
| 2" | 60.3 | 38 |
| 3" | 88.9 | 51 |
| 4" | 114.3 | 64 |
| 6" | 168.3 | 89 |
| 8" | 219.1 | 102 |
| 10" | 273.1 | 127 |
| 12" | 323.9 | 152 |
| 16" | 406.4 | 178 |
| 20" | 508.0 | 229 |
| 24" | 610.0 | 267 |
Full chart: ASME B16.9 fitting dimensions.
SS 904L Cap — questions buyers ask
Can a cap take full line pressure?
Yes — a buttweld cap of matching schedule is rated like the pipe it closes.
Can SS 904L caps be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
Which standard covers SS 904L caps?
The material is ASTM A403 WP904L (buttweld) · ASTM A182 F904L (forged); dimensions follow ASME B16.9 · B16.11. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 904L cap?
The alloy price, the size and schedule or class, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 or 3.2 certificates available on request / as specified in the PO; dimensional reports as required. PMI can be arranged depending on product and requirements, as specified in the PO.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026