valves

Valves are mechanical devices in piping and fluid handling systems that regulate the flow of liquids, gases, or slurries by opening, closing, or partially restricting passages. They provide isolation, direction, throttling, and pressure control and are used across industrial, commercial, and municipal infrastructures.

Common valve types include gate valves, globe valves, ball valves, butterfly valves, and check valves. Gate valves use a rising or non-rising metal gate to provide a straight path when open and are typically used for full-flow isolation but not throttling. Globe valves employ a baffle-like disc and provide good throttling control. Ball valves use a spherical ball with a bore that aligns with the flow; they offer rapid on/off action and are suitable for many applications. Butterfly valves use a rotating disc to regulate flow and are lightweight for large diameters. Check valves are non-return devices that prevent backflow. Other varieties include needle valves for precise small-flow control, diaphragm valves for corrosive or hygienic services, and pinch valves for granular media.

Actuation can be manual or automatic. Manual actuators include handwheels, levers, and taps. Automated actuation uses electric motors, pneumatic cylinders, or hydraulic cylinders linked to control systems, sometimes with positioners, sensors, and interlocks to respond to process signals and safety requirements.

Valves are made from materials chosen for chemical compatibility, temperature, and pressure, including brass, bronze, stainless steel, cast iron, and ductile iron. Sizing involves flow coefficient (Cv) and pressure rating (ANSI/ASME, API, or DIN standards). Installation considerations include orientation, downstream leakage, seating surface, and accessibility for maintenance.

Maintenance typically involves inspection of packing, seals, seating surfaces, and actuators, along with periodic testing for leaks and proper operation. Proper selection and sizing are essential to ensure reliable performance and system efficiency.