Clearing a food plant’s CIP hygiene audit with a surface finish change
Wetted surface roughness, verified per lot
Ra 3.2 µm (previous supply)Ra 0.6 µm average, 0.8 µm maximum
Measured over a 110-day programme
Volume
1,240 flanges, DN40–DN80, in two campaigns
Client
Dairy processor, Italy
The situation
A dairy processor in northern Italy failed a CIP (clean-in-place) hygiene audit because product residue was retained in flange surface irregularities at Ra 3.2 µm, which was the finish its previous supplier quoted as standard.
What was done
- The requirement was re-specified against a measurable acceptance test before any price was discussed — in this case wetted surface roughness, verified per lot measured on incoming goods, not on a supplier’s own paperwork.
- Process control was changed to hold that measurement: standard at DIN 2633 (EN 1092-1 Type 11 Form B), nominal size at DN50 (2").
- Evidence was tied to each lot so the buyer could verify the claim rather than trust it. That is why the programme ran 110 days: the first 6 lots were used to prove stability before volume was released.
Evidence you can ask to see
Surface roughness measurement records per lot, 100% positive material identification reports, ASTM A380 passivation certificates
These are buyer-side or third-party records, not supplier marketing. Where a document is commercially sensitive we will ask the buyer for permission before sending it, and say so rather than sending a redacted page that proves nothing.
The part involved
| Standard | DIN 2633 (EN 1092-1 Type 11 Form B) |
|---|---|
| Nominal size | DN50 (2") |
| Pressure rating | PN16 |
| Material | 316L stainless (1.4404), forged blank |
| Wetted surface roughness | Ra ≤ 0.8 µm, internal |
| Surface finish | Pickled and passivated to ASTM A380 |