What is valve trim and why is material selection important?

Valve trim includes the internal wetted parts that contact the process fluid: plug, seat ring, cage, stem, and guides. Material selection based on: corrosion resistance (process fluid compatibility), erosion resistance (high velocity, particulates), temperature capability (cryogenic to high-temperature), and hardness (for tight shutoff and wear resistance). Common materials: 316SS (general purpose), Alloy 6 (Stellite for erosion), Hastelloy (corrosive), and ceramic (severe erosion). Proper trim selection ensures reliable operation and long service life. Material combinations affect galling tendency.