SS 310 / 310S CapASTM A403 · ASME B16.9 · Manufacturer, trader & exporter, India
AISI 310S · UNS S31008
An SS 310 / 310S cap is a fitting that closes the end of a pipe, made from SS 310 / 310S to ASTM A403 WP310S (buttweld) · ASTM A182 F310 (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.
- 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 310 / 310S Cap?
- What it is
- A fitting that closes the end of a pipe
- Material
- ASTM A403 WP310S (buttweld) · ASTM A182 F310 (forged)
- Dimensions
- ASME B16.9 · B16.11
- Grade
- SS 310 / 310S · UNS S31008
- Best at
- Furnaces, burners and heat treatment at high temperature
SS 310 / 310S Cap Specification
| Product | SS 310 / 310S Cap |
|---|---|
| Material standard | ASTM A403 WP310S (buttweld) · ASTM A182 F310 (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 310 / 310S Cap: Why 310S 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 310 / 310S, 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 310 / 310S is picked for furnaces, burners and heat treatment at high temperature. |
|---|---|
| Typical service | Furnace parts — Muffles, retorts, radiant tubes and conveyor belts. |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER310 (AWS A5.9) |
SS 310 / 310S Cap Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
| Iron | 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 S31008.
SS 310 / 310S 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 S31008 — Annealed plate & sheet.
Full chemistry, properties and equivalents are on the SS 310 / 310S grade page.
Other SS 310 / 310S pipe fittings
SS 310 / 310S 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 310 / 310S 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 310 / 310S 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 310 / 310S caps?
The material is ASTM A403 WP310S (buttweld) · ASTM A182 F310 (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 310 / 310S 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