| Please help improve this article by adding citations to | | | | large enough to crush object in the pipe. On 100 kPa |
| reliable sources. Unsourced material may be | | | | input, you could lift a small car (upwards 1,000 lbs) |
| challenged and removed. (December 2009) | | | | easily, and this is only a basic, small pneumatic valve. |
| A pneumatic actuator converts energy (in the form of | | | | However, the resulting forces required of the stem |
| compressed air, typically) into motion. The motion can | | | | would be too great and cause the valve stem to fail. |
| be rotary or linear, depending on the type of actuator. | | | | This pressure is transferred to the valve stem, which is |
| Some types of pneumatic actuators include: | | | | hooked up to either the valve plug (see plug valve), |
| Tie rod cylinders | | | | butterfly valve etc. Larger forces are required in high |
| Rotary actuators | | | | pressure or high flow pipelines to allow the valve to |
| Grippers | | | | overcome these forces, and allow it to move the |
| Rodless actuators with magnetic linkage or rotary | | | | valves moving parts to control the material flowing |
| cylinders | | | | inside. |
| Rodless actuators with mechanical linkage | | | | Valves input pressure is the "control signal." This can |
| Pneumatic artificial muscles | | | | come from a variety of measuring devices, and each |
| Speciality actuators that combine rotary and linear | | | | different pressure is a different set point for a valve. A |
| motionrequently used for clamping operations | | | | typical standard signal is 20100 kPa. For example, a |
| Vacuum generators | | | | valve could be controlling the pressure in a vessel |
| A Pneumatic actuator mainly consists of a piston, a | | | | which has a constant out-flow, and a varied in-flow |
| cylinder, and valves or ports. The piston is covered by | | | | (varied by the actuator and valve). A pressure |
| a diaphragm, or seal, which keeps the air in the upper | | | | transmitter will monitor the pressure in the vessel and |
| portion of the cylinder, allowing air pressure to force | | | | transmit a signal from 20100 kPa. 20 kPa means there |
| the diaphragm downward, moving the piston | | | | is no pressure, 100 kPa means there is full range |
| underneath, which in turn moves the valve stem, which | | | | pressure (can be varied by the transmiters calibration |
| is linked to the internal parts of the actuator. Pneumatic | | | | points). As the pressure rises in the vessel, the output |
| actuators may only have one spot for a signal input, | | | | of the transmitter rises, this increase in pressure is sent |
| top or bottom, depending on action required. Valves | | | | to the valve, which causes the valve to stroke |
| require little pressure to operate and usually double or | | | | downard, and start closing the valve, decreasing flow |
| triple the input force. The larger the size of the piston, | | | | into the vessel, reducing the pressure in the vessel as |
| the larger the output pressure can be. Having a larger | | | | excess pressure is evacuated through the out flow. |
| piston can also be good if air supply is low, allowing the | | | | This is called a direct acting process. |
| same forces with less input. These pressures are | | | | |