What design considerations apply to severe service control valves?

Severe service applications involve high pressure drop, cavitation, flashing, high temperature, corrosion, or erosion. Design features: multi-stage trim (reduces pressure in steps, avoiding cavitation), hardened materials (Stellite, ceramic for erosion), special metallurgy (Hastelloy, Inconel for corrosion/temperature), heavy-duty construction (thick walls, reinforced packing), and extended bonnets (cryogenic or high temperature). Example applications: letdown valves (high delta P), boiler feedwater (cavitation), sour gas (H2S corrosion), and cryogenic (LNG). Require detailed analysis, testing, and often custom designs.