Stainless steel reducing coupling, female/female 316, BSP threaded
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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 reducing coupling, female/female 316, BSP threaded
Stainless steel reducing coupling, female/female 316, tapped BSP (Rp to ISO 7-1) at both ends. This stainless steel BSP reducing socket joins two R male components of different sizes, in 21 size pairs from 1/4" × 1/8" to 3" × 2"1/2 (DN8 × DN6 to DN80 × DN65). PN 20 up to 40 °C, drinking water compliant.
Description of the stainless steel BSP reducing coupling
In plumbing, this threaded stainless steel pipe fitting takes a straight run from one diameter to another, with no welding or soldering. It is investment cast (lost wax) in CF8M (AISI 316) stainless steel, and designed, manufactured and inspected to ISO 4144.
The size pair is read large end first: a 3/4" × 1/2" (French size 20x27 × 15x21, DN20 × DN15) takes a 3/4" R male thread at one end and a 1/2" one at the other. The body has no flats: each end finishes in a band.
Stainless steel reducing coupling: technical specifications
| Material | CF8M (AISI 316) stainless steel |
| Manufacture | Investment casting (lost wax) |
| Standard | Designed, manufactured and inspected to ISO 4144 |
| Thread | Rp1 and Rp2 tapped (parallel) to ISO 7-1 (BSP, R series). Mate with an R male thread (taper). Not compatible with NPT |
| Connection | Female/female |
| 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 | 21 size pairs, from 1/4" × 1/8" to 3" × 2"1/2 |
| 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 reducing coupling is used on drinking water systems and on circuits carrying fluids compatible with 316 stainless steel. For two male threads of the same size, choose a stainless steel female/female coupling; between two tapped ports, a stainless steel male/male reducing nipple. Check fluid compatibility and the permissible pressure at the working temperature.
- Thread sealing: an Rp/R joint seals on the threads, using PTFE or jointing compound suited to the fluid and the working temperature.
- Galling: with stainless steel on stainless steel, the thread can gall. Screw in gradually, without forcing.
- Tightening: as the reducing coupling has no flats, hold it with a strap wrench. Tighten with an open-ended or adjustable spanner on the flats of the male component (a strap wrench on pipe), not with pipe grips or pliers, which mark stainless steel.
- Dissimilar metals: on a water system, stainless steel forms a galvanic couple with galvanized steel or cast iron. On the brass side, with few exceptions, our flat-seal and conical-seat fittings are threaded to ISO 228-1 (BSPP, parallel), not R male.
Technical drawing
Dimensions (mm)
Dimensions in millimetres, PN in bar, weight in kilograms. ØB and ØD: outside diameters of the large end (Rp1), at the band and on the body. ØA and ØC: the same diameters at the small end (Rp2). L1: length of the small end. L2: overall length. ØC for the 3/4" × 3/8" and ØD for the 1" × 1/4" are not currently available: contact us if you need them.
| Rp1 × Rp2 size | French size | ØA | ØB | ØC | ØD | L1 | L2 | PN (bar) | Weight (kg) |
|---|---|---|---|---|---|---|---|---|---|
| 1/4" × 1/8" | 8x13 × 5x10 | 14.5 | 21 | 13 | 18 | 9 | 26 | 20 | 0.029 |
| 3/8" × 1/8" | 12x17 × 5x10 | 14.5 | 23.5 | 12.5 | 21.5 | 9 | 28 | 20 | 0.037 |
| 3/8" × 1/4" | 12x17 × 8x13 | 17.5 | 24 | 15.5 | 22 | 11 | 30 | 20 | 0.041 |
| 1/2" × 1/4" | 15x21 × 8x13 | 17.5 | 27.5 | 15.5 | 25.5 | 13.5 | 34.5 | 20 | 0.056 |
| 1/2" × 3/8" | 15x21 × 12x17 | 21 | 27.5 | 19 | 25.5 | 13 | 34 | 20 | 0.053 |
| 3/4" × 1/4" | 20x27 × 8x13 | 17.5 | 32.5 | 15.5 | 30.5 | 10 | 34 | 20 | 0.062 |
| 3/4" × 3/8" | 20x27 × 12x17 | 21 | 32.5 | – | 30 | 12 | 35.5 | 20 | 0.068 |
| 3/4" × 1/2" | 20x27 × 15x21 | 27.5 | 32 | 25 | 30 | 13.5 | 37 | 20 | 0.076 |
| 1" × 1/4" | 26x34 × 8x13 | 17 | 40 | 15 | – | 10.5 | 37 | 20 | 0.098 |
| 1" × 3/8" | 26x34 × 12x17 | 21 | 40.5 | 19 | 38 | 12 | 38.5 | 20 | 0.116 |
| 1" × 1/2" | 26x34 × 15x21 | 28 | 40.5 | 25.5 | 38.5 | 18 | 42 | 20 | 0.124 |
| 1" × 3/4" | 26x34 × 20x27 | 32.5 | 40.5 | 30 | 38 | 15 | 42 | 20 | 0.128 |
| 1"1/4 × 1/2" | 33x42 × 15x21 | 27.5 | 49.5 | 25.5 | 47.5 | 17 | 48 | 20 | 0.186 |
| 1"1/4 × 3/4" | 33x42 × 20x27 | 32.5 | 49.5 | 30.5 | 47 | 18.5 | 48.5 | 20 | 0.171 |
| 1"1/4 × 1" | 33x42 × 26x34 | 40 | 49.5 | 38.5 | 48 | 20.5 | 48 | 20 | 0.190 |
| 1"1/2 × 3/4" | 40x49 × 20x27 | 32.5 | 55.5 | 30.5 | 53.5 | 18.5 | 51.5 | 20 | 0.239 |
| 1"1/2 × 1" | 40x49 × 26x34 | 39.5 | 55.5 | 37.5 | 53.5 | 21 | 52 | 20 | 0.232 |
| 1"1/2 × 1"1/4 | 40x49 × 33x42 | 49 | 55.5 | 47.5 | 53.5 | 23.5 | 52.5 | 20 | 0.232 |
| 2" × 1"1/4 | 50x60 × 33x42 | 49.5 | 67.5 | 47.5 | 65.5 | 23.5 | 58.5 | 20 | 0.350 |
| 2" × 1"1/2 | 50x60 × 40x49 | 55.5 | 67.5 | 53.5 | 65.5 | 23.5 | 57 | 20 | 0.364 |
| 3" × 2"1/2 | 80x90 × 66x76 | 84.5 | 97.5 | 82 | 95 | 29.5 | 71.5 | 20 | 0.817 |
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).
| French size | 5x10 | 8x13 | 12x17 | 15x21 | 20x27 | 26x34 | 33x42 | 40x49 | 50x60 | 66x76 | 80x90 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Inches | 1/8" | 1/4" | 3/8" | 1/2" | 3/4" | 1" | 1"1/4 | 1"1/2 | 2" | 2"1/2 | 3" |
| DN | DN6 | DN8 | DN10 | DN15 | DN20 | DN25 | DN32 | DN40 | DN50 | DN65 | DN80 |
| OD (French size) | 10 mm | 13 mm | 17 mm | 21 mm | 27 mm | 34 mm | 42 mm | 49 mm | 60 mm | 76 mm | 90 mm |
Stainless steel reducing coupling: frequently asked questions
Reducing coupling or male/female reducing bush?
The reducing coupling takes two R male threads. The stainless steel male/female reducing bush screws into a tapped port of the larger size and takes a male thread of the smaller size. At 3/4" × 1/2", the reducing coupling is 37 mm long and the reducing bush 26 mm.
What if the size pair you need does not exist?
Combine two fittings: for a 2" × 1", screw a 1"1/2 × 1" reducing bush into a 2" × 1"1/2 reducing coupling.
What is the pressure rating at 150 °C?
≈ 15 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 male/female reducing bush, stainless steel union PN 20.
Other materials: brass reducers, black malleable iron reducers.
Useful guides:
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