Valves are mechanical or electromechanical devices that regulate the flow of liquids, gases, powders, and other materials through pipes or tubes and from tanks or other containers. Valves depend on a mechanical barrier—a plate, a ball, or a diaphragm, for example—that can be inserted and removed from the flow stream of the material going by in most cases. Some valves are designed to be on-off, while others allow for very fine control of media flow. We’ve gone through the specifics of various types of valves in this article.
Valves: Their Types and Functions
Aerosol Valves
The contents of aerosol cans are dispensed using aerosol valves. They are made up of two main parts: the housing and the stem. The intended use, output type, valve size, actuator type, and construction materials are important considerations. The type of media that is transmitted may also be a factor. Aerosol valves dispense creams, liquids, and ointments, gases, cleaning agents, and any other substance packaged in an aerosol can.
Air Logic Valves
Air Logic Valves are mechanical or electromechanical devices that regulate airflow in pneumatic systems and can be used instead of electrical control when electrical control is impractical, such as in dangerous atmospheres. Actuator type, number of ports, construction materials, switching speed, port thread size, pressure ratings, and input voltage are all essential specifications. Pilot valves, E-stops, one-shot valves, and other pneumatic logic valves are used in pneumatic systems.
Balancing Valves
Balancing Valves regulate fluid flow by splitting it equally between several flow branches. The number of port connections, ports, valve size, and construction materials are all essential considerations. Balancing valves are mainly used in HVAC and fluid control applications. They can be used in commercial heating/cooling systems, for example, to change water temperatures in response to changing load conditions. They can also be used to counterbalance double-acting cylinders.
Ball Valves
Ball valves are quarter-turn valves with swiveling ported spheres that block or allow flow in the pipe stream. There are special designs available that allow for some flow control. The number of ports, port layout, port connections, valve size, and the materials that make up the valve body, bench, seal, and stem packing are all essential specifications. Ball valves are used almost everywhere from a compressed-air line to a high-pressure hydraulic system; a fluid flow must be turned off. Since a ball valve port can be precisely matched to the pipe diameter, it can provide low head-loss characteristics. Ball valves seal better than butterfly valves, but they are more expensive to buy and maintain. They are normally operated with a lever that gives a visual indicator of the valve’s status.
Check Valves
Check valves allow only one direction of fluid flow through them. Lift-type check valves are similar to globe valves in that they use a ball or piston, which is also backed by a spring, to open at a certain pressure but close as the pressure drops, preventing backflow. These valves are sometimes used in high-pressure situations. The stop check valve, which also serves as a shut-off valve, is a variation.
Swing check valves have hinged gates, disc wafers, or spring-actuated wafers that close against ports as pressure drops. In low-pressure applications, these devices may be useful. The theme is changed slightly with a tilting disc check valve, which hinges the gate slightly inward to reduce the pressure needed for opening.
Rubber check valves come in a range of shapes and sizes, including flap and duckbill styles. Check valves are used on gas lines, airlines, and pumps—anywhere where fluid would flow in one direction. They can be miniaturized, made of plastic, and have a range of unique features, such as metal seats.
Faucet Valves
Faucet Valves are used to regulate the flow of water into basins or sinks. They usually do not have outlet connections, but some do have threads for connecting hoses, known as a hose bibb or spigot. Actuator type, Valve type, port connections, valve size, and the material that makes up the valve frame, including the seat, lining, seal, and stem packing, are important requirements. Another factor to remember is the mounting style.
Faucet valves are often used in labs, on containers, and as hose bibbs and can be made of low-cost materials that can be recycled after a container’s contents have been emptied.
Gate Valves
Gate valves are often used to stop fluid flow and are less commonly used for flow control. A gate valve uses a plate-like barrier that can be lowered into the flow stream to stop the flow. Its operation is alike to that of a globe valve, except that when the valve is completely opened, the gate delivers less flow constraint than a globe-valve plug. Port configuration, port connections, valve size, and the materials that make up the valve body, bench, seal, covering, and stem packing are essential requirements. Wedge-shaped plugs or parallel plates may be used in gate valves. Plugs typically seal the valve on both the upstream and downstream faces, while plates usually only seal the upstream face. Wedges come in a range of shapes and sizes to help minimize or accommodate sealing surface wear. While gate valves have a lower head loss when open than globe valves, they are not ideal for throttling and do not have the same positive shut-off as globe valves. Gate valves are used to cut off and separate operations in wastewater systems, power plants, and manufacturing plants.
Globe Valves
Globe Valves are named for using a globe-shaped disc that restricts flow by closing against a limiting orifice. They were once known for their spherically shaped bodies. The disc is opened and closed with a handwheel; on automatic valves, the disc is opened and closed with an actuator and sliding shaft. Valve shape, port connections, valve size, port configuration, and materials that make up the valve frame, such as the bench, seal, lining, and stem packing, are important considerations. Globe valves are used in wastewater treatment plants, food production plants, and processing plants, for example, shut-off and control. The Z-style valve is the most common type, so named because of the fluid’s path through the valve body. The design’s comparatively high head losses are due to the two right-angle turns that the fluid must make through the valve. The Y-style valve, which has the valve stem angled at 45 degrees to the valve frame, is a less restrictive design. The angle valve, which turns the flow 90 degrees, is another kind.
