DIN 11851 Coupling
The DIN 11851 coupling, better known as the dairy coupling, has been the most widely used screw coupling in the food industry for many years. Thanks to its round thread design and generous tolerances, this coupling can be closed without issues in nearly all practical situations. Even under less ideal conditions, a leak-free connection is possible, if necessary with a modified gasket. This makes the coupling extremely user-friendly and explains its continued popularity.
Although more modern alternatives are now available, this classic remains a favourite due to its easy installation and wide range of applications. The DIN 11851 coupling is officially standardised in NW sizes, but versions are also available in inch and ISO dimensions. Many fittings and instruments are equipped with a DIN 11851 coupling part, ensuring a high level of compatibility within existing installations.
SKS offers both forged and cast versions in its range. However, the cast version is not available with certificates at SKS. The couplings comply with the dimensional and material standards according to DIN 11850 and EN 10357. To ensure quality, the standard requires the use of forged raw material.
DIN 405-1 and 2, DIN 11887, DIN ISO 2768-1, ISO 48, FDA and BGA Versions and codes:
- Point D,
- Threaded piece C,
- Gland F and seal G; internal Ra value < 1.6µm
Other connections not standardized: Blind, Hose tail, screw-in or screw-on. Seals EPDM, FKM (Viton), HNBR, MVQ (silicone), NBR or PTFE (Teflon)
Seals
EPDM, FKM (Viton), HNBR, MVQ (silicone), NBR or PTFE (Teflon)
- DN10 – DN40 max. 40 bar
- DN50 – DN100 max. 25 bar
- DN125 – DN150 max. 16 bar
- DN200 max. 10 bar
Particularities
In accordance with EHEGD if fitted with SKS seal or in combination with the SKS adapter and seal.
DIN 11851 dimensions
DIN Reihe 1 and 2 tube sizes adhere to the DIN 11851 standard, with SKS providing these couplings in various systems including DIN Reihe 1, DIN Reihe 2, inch, and ISO. While DIN Reihe 1 dairy couplings may be scarce in the market, SKS consistently maintains them in stock, serving as your premier distributor.
| DIN Reihe I (standard) | DIN Reihe II (standard) | ISO | INCH |
| 12 x 1,5 | 13 x 1,5 | 17,2 x 1,6 | 12,7 x 1,65 |
| 18 x 1,5 | 19 x 1,5 | 21,3 x 1,6 | 19,05 x 1,65 |
| 22 x 1,5 | 23 x 1,5 | 26,9 x 1,6 | 25,4 x 1,65 |
| 28 x 1,5 | 29 x 1,5 | 33,7 x 2,0 | 38,1 x 1,65 |
| 34 x 1,5 | 35 x 1,5 | 42,4 x 2,0 | 50,8 x 1,65 |
| 40 x 1,5 | 41 x 1,5 | 48,3 x 2,0 | 63,5 x 1,65 |
| 52 x 1,5 | 53 x 1,5 | 60,3 x 2,0 | 76,2 x 1,65 |
| 70 x 2,0 | 70 x 2,0 | 76,1 x 2,0 | 101,6 x 2,10 |
| 85 x 2,0 | 85 x 2,0 | 88,9 x 2,0 | |
| 104 x 2,0 | 104 x 2,0 | 114,3 x 2,3 | |
| 129 x 2,0 | 129 x 2,0 | 139,7 x 2,6 | |
| 154 x 2,0 | 154 x 2,0 | 168,3 x 2,6 | |
| 204 x 2,0* | 204 x 2,0* | ||
- Tube size 12 mm to 41 mm: 40 bar
- Tube size 52 mm to 104 mm: 25 bar
- Tube size 129 mm to 154 mm: 16 bar
- Tube Size: Denoted by DN size, measuring pipe size.
- Standards: Adhering to DIN 11851.
- Material: Typically 1.4301 / 1.4307 / 1.4404 / 1.4432.
- Heat Number: Unique code for product origin identification.
One common query is, "Which part should be welded onto the installation?" Typically, the threaded piece is welded, as it maintains the seal and is less prone to damage.
SKS produces these couplings from forged materials, offering options in 1.4301 (304) and 1.4404 (316L) grades, complying with DIN EN 10088-3 standards. Default internal roughness is Ra <0.8μm, with available 3.1 certificates according to EN 10204.a
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