Trim is everything inside that controls and seals the flow, as opposed to the pressure-containing body and bonnet. Material choice is driven by erosion, corrosion and galling: gate and globe valves carry API trim numbers such as Trim 8, which pairs a 13 percent chromium stem with hardfaced seats, while control valves get hardened or staged trims for severe pressure drops. Changing the trim can resize a control valve without touching the body.
Valve's in fine shape, it just needs reduced trim, we can't control at 8 percent open all day.
Ordering a gate valve with the wrong trim number for the service is a common way to get galled seats in a year.
Also heard as
- internals
- valve trim
Related terms
Seat
The surface inside a valve that the closure member presses against to stop flow.
Disc
The movable closure element that seats to stop flow in globe, check, safety and butterfly valves.
Cage
A slotted or drilled sleeve around a control valve plug that guides it and shapes how flow changes with travel.
Control valve
A power-operated valve that modulates flow on a controller signal to hold pressure, level, flow or temperature at setpoint.
Stem
The rod that carries motion from the handwheel, lever or actuator through the bonnet to the closure member.