Ra 0.8 µm or smoother is the number usually quoted for stainless surfaces that touch product, based on EHEDG and 3-A guidance. It isn’t needed on every surface in the plant. A University of Southampton review found no clear link between roughness and bacteria sticking up to about Ra 1.37 µm, and concluded heavy polishing is rarely worth it. So set the finish by area: product contact, splash zones and structure can each have their own requirement.
Where the wash-down water is chlorinated, use 316; 304 gets attacked over time. Welding leaves heat tint, which is where corrosion tends to start. TIG gives a clean, controlled weld with little spatter and tint, so the seam can be finished flush without heavy grinding. If your spec calls for pickling or passivation (ASTM A380 and A967 cover cleaning and passivating stainless parts), tell us and we’ll confirm how we handle it.
180 m of trench in 2 mm 316 stainless, 300 mm wide and 200 mm deep, with a 1% fall. Parts were CNC cut and folded on the press brake to one profile, then laser marked so the long run went together in the right order on site. Every weld was TIG, continuous and ground flush, and a removable grating sits on top. Read the full case study.
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Not everywhere. It makes sense where wash-down is chlorinated, as at Baladi, because 304 gets attacked over time. Dry areas often use 304. Follow your food safety consultant and audit requirements.
Ra 0.8 µm or smoother is usual for product contact surfaces. Set it by area rather than one number everywhere.
We fabricate in our workshop and install finished sections, so time on site is short. Put your shutdown window in the RFQ.
Check the numbers against the current edition of each standard and your project spec.