Butt-Weld to EN 10253
Butt-weld fittings (elbows, tees, reducers, caps) to EN 10253-3 and -4 for stainless steel. Dimensions follow European pipes (EN ISO 1127), with type A or B for the wall.
For European projects and EN pipes
Four families that are often confused because they look alike. The standard decides the dimensions, wall, pressure and what can be connected to what. Here we compare them side by side.
Butt-weld fittings (elbows, tees, reducers, caps) to EN 10253-3 and -4 for stainless steel. Dimensions follow European pipes (EN ISO 1127), with type A or B for the wall.
For European projects and EN pipes
Austenitic stainless butt-weld fittings with ASME B16.9 dimensions and Sch 10S, 40S, 80S walls. Class WP-S is seamless; SA403 is the version for the ASME pressure vessel code.
For ASME code projects and refineries
Threaded stainless fittings (elbows, tees, couplings, nipples, plugs) with ISO 7-1 threads (tapered BSP), usually cast, for low to medium pressure lines.
For general installations with BSP threads
Heavy forged fittings to ASME B16.11 with socket weld (SW) or NPT thread, for small bores and high pressure.
For high pressure and small bores
Scroll the table sideways on a phone. The first column stays fixed.
| Property | EN 10253 | A403 / SA403 | ISO 4144 | 3000 lbs |
|---|---|---|---|---|
| Standards | EN 10253-3 (general use) and EN 10253-4 (specific inspection requirements) | ASTM A403 / ASME SA403, dimensions ASME B16.9 (B16.28 for short radius elbows) | ISO 4144 (thread to ISO 7-1) | ASME B16.11, material ASTM A182 |
| Material and grades | EN 10088: 1.4301, 1.4307, 1.4404, 1.4571; duplex 1.4462 | WP304, WP304L, WP316, WP316L, WP321, WP347 | Cast CF8 (≈ 304) and CF8M (≈ 316) | F304, F304L, F316, F316L (ASTM A182) |
| What it includes | Elbows, tees, reducers, caps for butt welding | Elbows, tees, reducers, caps for butt welding | Elbows, tees, couplings, nipples, reducers, threaded plugs | Elbows, tees, couplings, plugs, nipples with socket or thread |
| Pipe connection | Butt weld | Butt weld | Tapered ISO 7-1 thread (R / Rp, BSP) | Socket weld (SW) or NPT thread |
| Manufacturing | Wrought, seamless or welded; type A or B | Seamless (WP-S) or welded (WP-W, WP-WX, WP-WU); SA403 for the ASME code | Usually investment cast | Forged from billet |
| Sizes | Diameters to EN ISO 1127, e.g. Ø33.7, Ø60.3, Ø88.9 mm | NPS ½ to 48 inch (ASME B16.9) | ⅛ to 4 inch (about DN6 to DN100) | NPS ⅛ to 4 inch |
| Wall / class | Per EN pipe; type A for thinner wall and lower pressure, type B for the full pipe wall | Sch 5S, 10S, 40S, 80S | Wall set by the manufacturer, no schedule | Classes 2000, 3000, 6000, 9000; 3000 SW usually matches Sch 80 pipe |
| Pressure | Calculated from the wall and type (A or B) | By wall (Sch) and temperature; accepted by the ASME code with SA403 | Low to medium; check the manufacturer's datasheet | High: set by the class and the ASME B16.11 pressure–temperature table |
| Pressure idea (≈ 20–38 °C) | Type B: same as a pipe of the same wall (see the table below). Type A: lower, by the pressure factor in the EN 10253-4 annex. | Same as pipe of the same Sch: e.g. DN50 Sch 40S ≈ 95 bar and Sch 80S ≈ 137 bar (316/316L, 38 °C). | Around 16 bar (PN16) is common; some suppliers quote 150 psi (≈ 10 bar) or PN20 (≈ 20 bar). | Class 3000: 3000 psi ≈ 207 bar at 38 °C for A182 F316; falls with temperature. |
| Installation | TIG butt welding; needs a qualified welder and inside gas purge | TIG butt welding; thicker walls need more weld passes | Screwed with sealant (PTFE or paste); no welding, quick | Fillet weld in the socket, or NPT thread with sealant |
| Joint inspection | Visual, PT and, per code, RT or UT | Visual, PT and, per code, RT or UT; WP-WX and WP-WU have mill weld examination | Leak test after installation | PT or MT on the socket weld; leak test for threads |
| Relative cost | Medium | Medium to high (thicker walls, more material) | Low | High per piece, but compact |
| Typical use | Process piping in Europe, food, beverage, water and general lines | Refineries, chemicals, oil and gas, ASME code pressure vessels | Water, air and general installations without high pressure | Instrumentation, hydraulic and high pressure small bore lines |
| Strengths | Matches European pipes; economical in thin walls; 3.1 traceability | Wide international acceptance; standardised walls; ASME code | Weld-free fitting, quick and cheap; easy to dismantle | Very high strength; compact joint; less affected by vibration |
| Limitations | Doesn't mix directly with ASME dimensions; thin wall in type A | Thicker Sch walls are heavier and pricier; not compatible with EN pipe without care | Not for high pressure; thread can leak with vibration or temperature; don't mix with NPT | Small bores only; NPT thread is not the same as BSP; pricier |
| Documentation | EN 10204 3.1 certificate per EN 10253-4; in -3 by agreement | Material certificate per ASTM A403 and EN 10204 3.1 on request | 3.1 certificate on request | Material certificate per ASTM A182 and 3.1 on request |
Sizes and classes summarise the standards; real parts vary by manufacturer. Always specify the full standard and ask for the manufacturer's table.
A quick comparison of the size of pressure you can expect from each family at ambient temperature. It is a rough idea, not a design value.
This pressure comparison is indicative only. For any specific project consult a professional engineer, who must calculate the design pressure according to the applicable code (EN 13480, ASME B31.3, etc.), the material, temperature, corrosion and safety factor. Do not use these values to judge the safety of a pressure system.
EN 10253 type B butt-weld follows the pressure of a pipe of the same wall, so it depends on the wall chosen and isn't shown as a single bar.
For ISO 4144 we did not find the official pressure–temperature table in public sources, so we give a range quoted by suppliers. Ask the manufacturer or the standard text for the exact value.
ASME B16.9 butt-weld fittings are rated as seamless pipe of the same material and Sch, so the table also applies to A403 and to EN 10253 type B with the same wall. Values are for A312 TP316/316L at 38 °C.
| Size | Sch 40S | Sch 80S | Sch 160 |
|---|---|---|---|
| DN25 · 1" | 152 bar(2205 psi) | 211 bar(3061 psi) | 310 bar(4493 psi) |
| DN50 · 2" | 95 bar(1371 psi) | 137 bar(1985 psi) | 226 bar(3283 psi) |
| DN100 · 4" | 76 bar(1102 psi) | 110 bar(1596 psi) | 180 bar(2611 psi) |
| DN200 · 8" | 53 bar(771 psi) | 84 bar(1218 psi) | 158 bar(2298 psi) |
The allowable pressure drops as temperature rises, because the allowable stress of the steel falls. Roughly, compared with the value at ambient temperature:
| Temperature | 38 °C | 204 °C | 316 °C | 371 °C | 399 °C |
|---|---|---|---|---|---|
| Allowable pressure | 100 % | 93 % | 81 % | 77 % | 75 % |
Values were collected from public sources on the internet, not from the full text of the standards (which are paid):
A starting point. Your project may have a special requirement.
Diameters and walls differ slightly: for example DN25 is 33.7 mm in EN and 33.4 mm in ASME. Don't connect them without confirming the dimensions and the weld.
Both are tapered but have a different profile and pitch (55° BSP, 60° NPT). Mixed, they may seize without sealing and leak. ISO 4144 is BSP; threaded 3000 lbs is NPT.
The ASME B16.11 classes are for small bores with socket or thread. For larger sizes choose butt-weld fittings to EN 10253 or A403.
State the standard, grade, wall (Sch or mm) and whether a 3.1 certificate is needed. That avoids changes at delivery.
This comparison is indicative and does not replace the standard or the designer's calculation. For critical projects use the full texts of the standards and the manufacturer's tables.
Not sure which standard you need? Send us the project or specification and we'll help you choose.