Pneumatic valves circulate air throughout a larger pneumatic system by either allowing or inhibiting the flow of pressurized air, whose force is then used to power a device. Because valves can have varying numbers of entryways for air, creating different flow patterns, valves are classified according to the number of ports they possess and the flow-paths they create. Additionally, because they can move air in a variety of ways they can suit a variety of applications. Aside from the commonly used directional control valves, there are valves that are designed to serve more specific purposes, such as pressure regulator, venting-type regulator valves, and needle valves. Pressure and venting-type valves both help control pressure, whereas needle valves help control the flow within a pneumatic system.
A pressure regulator is responsible for preventing pressure fluctuation by controlling pressure as it is coursed through an actuator or another part of a pneumatic system. In order to air pressure within an appropriate pressure range, the pressure should be set low enough so that it can fluctuate between 3 and 5 psi without altering the minimum and maximum pressure system requirements. In certain applications, a pressure regulator valve must ensure that air-pressure output stays at a constant regardless of changes in pressure at earlier points in the system and changes in flow. Other applications require pressure regulators to lower pressure so that air isn’t wasted while still meeting the basic pressure requirements of the device.
Pressure regulators work with sensors to monitor the pressure as it expands as it moves through a pneumatic system. Once the pressure has reached the maximum level of expansion, a sensor is triggered by the high pressure, which in turn signals to the pressure valve to close thus cutting off pressure. As a result of the pressure valves opening and closing in response to pressure levels, pressure is kept at a relatively constant level as it reaches the actuator or other pneumatic device.
A venting-type regulator functions in much the same way as a pressure regulator does, but also acts as a small exhaust valve to help maintain a constant pressure balance be allowing some of the pressure to exit. There are two ways the excess pressure can be released: an internal bleeding system or an external bleeding system. In an internal bleeding system a venting regulator simply re-routes the additional pressure. In an external bleeding system a venting regular allows the excess pressure to completely exit the system. However, this kind of venting system is not suggested for use with large-flow systems because large volumes of air cannot be released through a venting-type regulator. Additionally, instead of letting the pressure expand, a venting-type regulator monitors the pressure to ensure it remains at a level below that at which it enters the pneumatic system and passes through the venting-type regulator.
Needle valves are used to help control flow by resticting the amount of air the allow through. In order to restrict of slow down flow, the valve features an adjustable component positioned so as to prevent an actuator or other device from releasing more air than the system can handle at a given time, thus helping maintain a constant flow rate. The adjustable component resembles a needle, which can be screwed into place to block the actuator. As a result of a tightened needle valve, the flow of air not only decreases but backs up inside the actuator, inhibiting the actuator from generating more pressue because of the increase in resistance. A needle valve can be used to reverse the flow of a system or to maintain a constain flow rate.
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