industrial instrumentation basics

Every process plant runs on valves — isolating equipment for maintenance, throttling flow, preventing backflow, and protecting against overpressure. While our Control Valve Basics post covers automated, actuated control valves specifically, this post covers the broader family of valve types you'll find throughout a plant — on/off, isolation, and specialty designs — and where each one fits. On/Off (Isolation) vs. Control Valves Before getting into specific types, it's worth separating valves into two broad functional categories: On/off (isolation) valves — designed to be either fully open or fully closed, used to isolate a section of pipe or equipment, typically for maintenance. Most aren't designed for throttling and will wear prematurely or perform poorly if used that way. Control valves — designed to modulate to any position between fully open and fully closed, precisely regulating flow, pressure, or level in response to a continuous control signal. Common V...