Polished stainless steel butt-weld reducer joining two tube sizes. DIN 11852 makes two patterns — concentric (RK) and eccentric (RE), the latter for horizontal lines that must drain — and the pattern must be stated when ordering.
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A reducer joins two tube sizes with a smooth conical transition, so the bore steps down without a shoulder that would trap product or disturb the flow. Like the other hygienic tubular fittings it is formed from tube and the internal finish carries through.
DIN 11852 distinguishes the concentric reducer, RK, from the eccentric, RE, and the choice is a process decision rather than a preference. A concentric reducer is symmetrical about the axis and is correct on a vertical line. On a horizontal line it leaves a pocket at the bottom of the cone that will not drain; the eccentric reducer, fitted flat side down, keeps the invert continuous so the line drains fully. Note also that on a reducer the DN size refers to the largest diameter.
Material is austenitic stainless steel, in practice 316L (1.4404) for wetted service, with the internal surface specified as an Ra value. Both ends are plain for butt welding, so the tube standard at each end must be given — a reducer between two different systems, say EN 10357-A on one end and ASME BPE on the other, is a special and has to be identified as one.
State both sizes and the tube standard at each end, the pattern — concentric or eccentric — the grade, the internal Ra and the surface condition, and ask for the EN 10204 3.1 certificate at the order stage.
| Patterns Stocked | Both the concentric (DIN 11852 RK) and the eccentric (RE) pattern are carried; state which on the order. Specify eccentric for a horizontal line that has to drain — a concentric reducer leaves a pocket at the bottom of the bore that CIP will not clear. |
|---|---|
| Fitting Type | Butt-weld reducer, plain ends. DIN 11852 patterns: RK concentric and RE eccentric. The eccentric pattern, fitted flat side down, is what a horizontal line that must drain requires. On a reducer the DN size refers to the largest diameter |
| Standard | DIN 11852 tubular fittings for DIN 11851 pipework; the ISO equivalents are ISO 2851 for bends and tees, and BS 4825-2 in the British hygienic series |
| Size Range | EN 10357-A (former DIN 11850 Reihe 2) tube, DN10 to DN200 — outside diameter 13, 19, 23, 29, 35, 41, 53, 70, 85, 104, 129, 154 and 204 mm. The DN label is neither the bore nor the outside diameter |
| Pressure Rating | DIN 11852 tubular fittings: 25 bar for DN10-DN50, falling above DN50 to between 5 and 10 bar at DN150-DN200, usable to a maximum of 150 °C. Bends, tees and reducers step down differently above DN50 |
| Material | Austenitic stainless steel; specify AISI 316L (1.4404) for wetted service or 304L (1.4307). DIN-system tube and fittings are normally EN 10217-7 |
| Surface Finish | Finely finished product-contact surfaces Ra < 1.0 µm, other surfaces Ra < 2.5 µm, weld seam Rmax ≤ 16 µm; hygienic practice for internal surfaces is Ra ≤ 0.8 µm |
| Applicable Hygiene Standard | 3-A 63-04 Sanitary Fittings is the applicable class for this type of equipment. The goods are not asserted to carry the 3-A Symbol |
| Certification to Specify | EN 10204 3.1 inspection certificate for wetted stainless steel parts |
