Pneumatic valves control the pressure, flow rate, direction, and amount of air that travels through a pneumatic system. Pneumatic systems are integral in countless industrial applications where they control a power source. While the medium in the system is fluid, such as in a hydraulic system, the way in which it is controlled is different. There are many types of pneumatic valves that can be used to control the pressure and flow of fluid. The most common of these are pressure relief valves, flow control valves, and directional control valves. In this blog, we will take a look at each type and its unique characteristics.
The pressure relief valve is a type of safety valve used to control or limit pressure in a system that might otherwise build up and create a process upset, instrument or equipment failure, or fire. The valve relieves pressure by allowing pressurized fluid to flow from an auxiliary passage out of the system. The valve is designed to open at a predetermined pressure such that the equipment is not exposed to pressure exceeding their design limits. If the set pressure is exceeded, the relief valve is forced open and a portion of the fluid is diverted through the auxiliary route. In a system with flammable fluids, such as gas, the diverted fluid is typically routed through a piping system known as a flare header to a central gas flare where it is burned off and the resulting gases are released into the atmosphere. Once the system returns to a stable pressure, the valve closes.
Flow control valves are used to regulate the flow and/or pressure of a fluid. Valves of this type commonly respond to signals generated by devices including flow meters and temperature gauges. They are commonly fitted with actuators and positioners. Pneumatically-actuated globe valves and diaphragm valves are predominantly used, although modified ball and butterfly valves are also used. Control valves can also work in conjunction with hydraulic actuators in a type of valve known as automatic control valves. The hydraulic actuators respond to changes in pressure and flow and respond by opening or closing the valve.
Finally, directional control valves are a type of flow control valve and one of the most fundamental parts of any hydraulic or pneumatic system. They allow for the flow of hydraulic oil, water, air, or other fluids into different paths from one or more sources. The typical directional control valve consists of a mechanically- or electrically-actuated spool inside a cylinder. The spool consists of lands and grooves. Lands block the flow of fluid through the valve body, while grooves allow the fluid to flow around the spool and through the valve body. The positioning of the spool either restricts or permits flow, thereby controlling the fluid flow rate.
Other types of pneumatic valves include poppet valves and spool valves, both of which have unique characteristics tailored to the application they are designed for. When considering which type of valve is ideal for your use, not that most come with either standard or non-standard mounting configurations. It is always best practice to research before purchasing a valve, as there will likely be inconsistencies in valves from different manufacturers.
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