Stainless steel butt weld union 316, PN 20, weld ends both sides
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| Product Type | Delivery Method | Preparation Time | Transport Time | Delivery Time |
|---|---|---|---|---|
| All Parts | Pickup Point | 0 to 3 days | 3 to 6 days | 3 to 9 days |
| All Parts | Home Delivery | 0 to 3 days | 3 to 5 days | 3 to 8 days |
| Tubes > 90cm | Home Delivery | 0 to 3 days | 3 to 5 days | 3 to 8 days |
| Tubes < 200cm | Home Delivery | 0 to 3 days | 3 to 5 days | 3 to 8 days |
| Tubes > 200cm | Home Delivery | 0 to 6 days | 6 to 10 days | 6 to 16 days |
| Assembled Products | Home Delivery & Pickup Point | 0 to 5 days | (see methods) | 3 to 11 days |
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Stainless steel butt weld union 316, PN 20, weld ends both sides
Stainless steel butt weld union 316, PN 20, with plain butt weld (BW) ends on both sides, from Ø 13.5 to Ø 60.3 mm (sizes 1/4" to 2", DN8 to DN50). It provides a point of disconnection on welded pipework. PN 20 up to 40 °C, drinking water compliant, for all fluids compatible with stainless steel.
Description of the stainless steel butt weld union 316 PN 20
This 3-piece stainless steel union consists of two weld ends and a nut. Both connections to the pipework are welded. Between the ends, the seal is metal to metal at the conical seat. Undoing the nut is enough to open the line, without cutting the pipe.
The whole union is investment cast (lost wax) in CF8M (AISI 316) stainless steel, and designed, manufactured and inspected to ISO 4144. The ends have no flats; only the nut has them.
At your temperature, does the working pressure exceed the PN 20 limit? See the stainless steel butt weld union 316L PN 40, from Ø 21.3 to Ø 60.3 mm, which has no high-temperature figures: for hot applications, contact us before choosing. Does one side need to screw on? Choose the stainless steel female/butt weld union PN 20 or the stainless steel male/butt weld union PN 20.
Stainless steel butt weld union: technical specifications
| Material | CF8M (AISI 316) stainless steel |
| Manufacture | Investment casting (lost wax) |
| Standard | Designed, manufactured and inspected to ISO 4144 |
| Type | Conical (taper) seat union, 3-piece: two weld ends and a nut |
| Seal at the seat | Metal to metal |
| Shape | Plain ends without flats, nut with flats |
| Connection | Butt weld (BW) at both ends; Ø = outside diameter of the end |
| Ends | 2 weld ends |
| Nominal pressure | PN 20: 20 bar from −20 to 40 °C, lower above that |
| Temperature | −20/+220 °C, permissible pressure reduced above 40 °C |
| Fluids | All fluids compatible with stainless steel |
| Sizes | 8 sizes, from Ø 13.5 to Ø 60.3 mm (1/4" to 2") |
| Compliance | 4MS; drinking water: French order of 25 June 2020 |
Pressure and temperature
PN 20 applies from −20 to 40 °C. Above that, the permissible pressure falls. Values marked ≈ are read from the pressure/temperature curve in the technical data sheet.
| Temperature (°C) | Max. pressure (bar) |
|---|---|
| −20 → 40 | 20 |
| 100 | ≈ 16.5 |
| 150 | ≈ 15 |
| 220 | ≈ 13.5 |
Certification and compliance
According to the technical data sheet for the series:
- 4MS: compliant with the 4MS requirements, the harmonized European rules for materials and products in contact with drinking water.
- Drinking water: compliant with the French order (arrêté) of 25 June 2020 on metallic materials and products in contact with water intended for human consumption.
Uses and installation advice
This union goes on welded pipework, wherever part of the line must be removable, on drinking water systems and on circuits carrying fluids compatible with 316 stainless steel. Check fluid compatibility and the permissible pressure at the working temperature.
- Welding: to be carried out by a qualified welder. The welding process and filler metal depend on the installation.
- Before welding: dismantle the union and separate the ends to protect the conical seat. Keep the seat clean at every reassembly.
- Galling: with stainless steel on stainless steel, the nut can gall. Screw it on gradually, without forcing.
- Tightening: tighten the nut with an open-ended or adjustable spanner, not with pipe grips or pliers, which mark stainless steel. As the ends have no flats, hold them with a strap wrench.
Technical drawing
Dimensions (mm)
A: overall length. Ø: outside diameter of the weld ends. B: outside dimension of the nut. Dimensions in millimetres, PN in bar, weight in kilograms.
| Size | French size | Ø | A | B | PN (bar) | Weight (kg) |
|---|---|---|---|---|---|---|
| 1/4" | 8x13 | 13.5 | 31.5 | 33 | 20 | 0.069 |
| 3/8" | 12x17 | 17.2 | 38 | 37 | 20 | 0.110 |
| 1/2" | 15x21 | 21.3 | 40.5 | 40 | 20 | 0.135 |
| 3/4" | 20x27 | 26.9 | 46 | 49.5 | 20 | 0.195 |
| 1" | 26x34 | 33.7 | 49 | 56 | 20 | 0.250 |
| 1"1/4 | 33x42 | 42.4 | 54 | 67 | 20 | 0.380 |
| 1"1/2 | 40x49 | 48.3 | 56 | 73 | 20 | 0.442 |
| 2" | 50x60 | 60.3 | 64 | 90 | 20 | 0.739 |
Size conversion
Conversion between the French size designation, inches, DN and the outside diameter stated in the designation (a rounded value, not a pipe dimension). The actual diameter of the end is dimension Ø.
| French size | 8x13 | 12x17 | 15x21 | 20x27 | 26x34 | 33x42 | 40x49 | 50x60 |
|---|---|---|---|---|---|---|---|---|
| Inches | 1/4" | 3/8" | 1/2" | 3/4" | 1" | 1"1/4 | 1"1/2 | 2" |
| DN | DN8 | DN10 | DN15 | DN20 | DN25 | DN32 | DN40 | DN50 |
| OD (French size) | 13 mm | 17 mm | 21 mm | 27 mm | 34 mm | 42 mm | 49 mm | 60 mm |
Stainless steel butt weld union: frequently asked questions
Why a union rather than a direct weld?
The nut opens the joint without cutting the pipework. The seal is then restored by metal-to-metal contact at the conical seat.
How do I read the diameter?
The size option gives the outside diameter of the end, followed by the size designation in inches: Ø 21.3 mm (1/2"). Approving the weld on your pipe is a matter for your welder.
What is the pressure rating at 100 °C?
≈ 16.5 bar, against 20 bar from −20 to 40 °C.
The appearance of the part may vary depending on the batch in stock. Contact us for confirmation.
See also
Full range: all stainless steel BSP fittings
Other stainless steel fittings: stainless steel female/female union PN 20 or stainless steel male/female union PN 20 for a screwed joint at both ends.
Other materials: brass fittings, black malleable iron unions.
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