Refining

The CDU is the primary processing unit in a refinery, separating crude oil into fractions by distillation at 350-380°C. Atmospheric and vacuum distillation columns require high-temperature gate valves for isolation and globe control valves for flow regulation. Vacuum section valves handle sub-atmospheric pressure without air ingress.

FCC units convert heavy gas oil into gasoline and propylene using catalyst at 500-700°C. Slide valves control catalyst circulation between reactor and regenerator. Erosion from catalyst particles requires hardened trim (Stellite overlay). Expansion joints and hot-wall valve designs accommodate thermal growth in the 600°C+ service.

Hydrodesulfurization and hydrocracking units operate at 350-450°C and 50-200 bar with hydrogen-rich gas. Valves in hydrogen service require special material selection to prevent hydrogen embrittlement — low-alloy steel (F22) with controlled hardness. Globe control valves regulate feed/effluent exchanger bypass for temperature control.

Alkylation units produce high-octane gasoline using sulfuric acid (SA) or hydrofluoric acid (HF) catalysts. HF alkylation requires Monel 400 or Hastelloy C valves with zero-leakage bellows seals to prevent deadly HF release. Isomerization units convert normal butane/pentane to isomers using catalyst chloride — requiring corrosion-resistant alloy valves.