Stainless steel gate valves: which media need them and how to pick the grade
A stainless steel gate valve costs several times more than a carbon steel one, so it is chosen where carbon steel or iron would fail quickly. Stainless steel is not universal either: some media attack it.
TAZ Engineering Team · · 6 min
Where stainless is needed
Chemical and petrochemical plants handling acids and alkalis, food and pharmaceutical production where product purity matters, demineralised water, some wastewater streams and cryogenic service. TAZ 30nzh41nzh austenitic gate valves are catalogued for temperatures up to 560 °C.
Main grades
12Kh18N9TL is a titanium-stabilised cast chromium-nickel steel to GOST. CF8 is the cast equivalent of AISI 304; CF8M of AISI 316 with molybdenum, more resistant to chlorides and some acids. CF3 and CF3M are low-carbon versions less prone to intergranular corrosion after welding.
Limits
Chlorides are the main threat to austenitic steels: at elevated temperature they cause pitting and stress corrosion cracking. Seawater and brines often need duplex steels or other alloys, and stainless steels are not resistant to hydrochloric acid. Always check the grade against corrosion data for the actual concentration and temperature.
Seats and packing
Seats are stainless or hardfaced; packing is PTFE or graphite depending on medium and temperature. In food plants all wetted materials need food-contact compliance.
Ordering
State the exact composition, concentration, temperature, chloride content, pressure and material certificate requirements. TAZ will propose the steel grade and sealing materials.
Checklist
- composition and concentration
- temperature
- chlorides
- pressure
- steel grade
- seat and packing materials
- food-contact requirements
- material certificates