The Basic Principles of How Valves Function
Valves are essential for keeping fluids moving in the right direction. They are found in many systems, including plumbing valves, taps for water and gas, safety devices fitted to hot-water heaters, and in the human heart and blood vessels. The basic principles of how valves function are the same, regardless of type or size. Valves can be manually operated or powered by pneumatic, hydraulic, electric, or mechanical actuators. The way a valve operates is determined by its design.
A valve is a membranous structure that temporarily closes a passage or orifice, permitting movement of a fluid in one direction only. A valve may consist of a muscle, two or three membranous flaps or folds called cusps, or a combination of these. Generally speaking, a valve will close when the pressure upstream exceeds the dynamic pressure downstream, which is caused by flow velocity. The difference between the dynamic and static pressure is called the valve’s differential.
The main job of a heart valve is to prevent blood from flowing backwards after the heart pumps blood. This happens when the tricuspid and mitral valves open and the aortic valve closes. The cusps of a heart valve help create the seal needed to keep blood from flowing backwards. If a heart valve becomes damaged or scarred (stenotic) and can’t form a tight seal, the heart must pump even harder to move blood forward through the valves.
Similarly, valves in industrial systems function to control rate of flow and maintain a desired level or pressure. The control valves used in such systems are designed to modulate flow through movement of the valve plug in relation to ports located within the valve body. The control valve’s port size and trim, and the way in which it is actuated, determine how quickly it can open or shut, and how precisely it can maintain a set point. For a Valve Manufacturer, contact https://orseal
Some valves are manually operated by turning a handle or crank. This moves a piston, plug, plate, or other controlling obstruction into the path of the pipe blocking access to it. Manually operated valves have a wide range of operating differentials allowing them to open or close at varying speeds. A manually operated valve can be actuated with handwheels, levers, gear wheels, or chains.
Pneumatic actuators, which are usually used to actuate ball valves, use an air or gas signal from an external source to produce a modulating control action. The signal passes through a diaphragm on the actuator, which, when energized, produces a force that acts across the valve stem to stroke the valve plug. This creates a gap or hole in the valve seat that stops or opens the flow of fluid passing through the valve.
