Semiconductor and pharmaceutical ultrapure media lines demand far more than ordinary industrial stainless:

1) Material: mainly 316L (or 316L VAR), low carbon and low inclusions; EP (electropolished) internal surfaces commonly require Ra ≤0.25–0.4 μm to reduce particle adhesion and ion release. 2) Fittings: use EP fittings of the same grade; avoid internal steps and crevices. 3) Welding: automatic orbital TIG with internal purge gas, smooth oxide-free internal welds; inspect with borescope and helium leak test. 4) Cleaning and packaging: ultrapure cleaning and double bagging in cleanroom bags; keep dry before installation. 5) Validation: particle, TOC and metal-ion release tests per project specification.

Purchasing reminder: require EP internal surface reports (Ra, SEM/EDS), welding procedure and clean packaging documentation; do not substitute ordinary BA/2B tube.

The core of ultrapure lines is not the grade but the system control of surface, welding and cleanliness.