Understanding More about Pneumatic Actuators
Posted in Uncategorised, on March 23, 2016 By Admin
Pneumatic actuators are used in a number of industries today for a variety of reasons based on the benefits provided. As an example, pneumatic actuators are responsible for converting energy into mechanical motion, which in most cases is in the form of compressed air. The motion into which the energy is converted may be linear or rotary depending on the type of actuator used.
Types of Pneumatic Actuators
There are actually several different types of pneumatic actuators, as outlined below:
- Grippers
- Pneumatic Artificial Muscles
- Rodless Actuators (with mechanical linkage)
- Rodless Actuators (with magnetic linkage or rotary cylinders)
- Rotary Actuators
- Specialty Actuators (combines linear and rotary motion)
- Tie Rod Cylinders
- Vacuum Generators
The Construction of a Pneumatic Actuator
Pneumatic actuators are primarily comprised of a cylinder, piston, and ports or valves. A seal or diaphragm covers the piston so that air within the upper part of the cylinder is maintained. As a result, air pressure forces the seal downward, which in turn moves the piston below followed by moving the valve stem connected to the actuator's internal components.
Based on the required action, a pneumatic actuator may have just one location for a signal input and be located on the bottom or the top. This is important to note and check in the event of a needed repair. As a general rule, the larger the piston size the more output pressure. If air supply were low then a larger piston would prove to be advantageous since the same forces are allowed with lower input. The control signal forms the valve input pressure, which can come from numerous types of measuring devices.
To better understand the magnitude of these pressures, they are big enough to crush objects within the pipe. For instance, with a 100 kPa input, a small car up to 1,000 pounds could be lifted with ease. Keep in mind that this is using just a very small and basic type of pneumatic actuator valve. Of course, because resulting forces placed on the stem would be tremendous, the valve stem would fail.
The control signal equates to the pneumatic valve input pressure, which can come from different measuring devices and of unique pressures with different set points. For instance, within a vessel that has a constant out-flow along with varied in-flow, the valve can control pressure. Monitoring this pressure is a pressure transmitter, which then transmits a signal between 20 and 100 kPa. If the pressure level reaches 20 it indicates there is no pressure while at 100 pressure is at full range.
The transmitter output will rise as pressure in the vessel increases. This pressure increase is then sent to the valve cause it to stroke downward and begin to close. Known as a direct acting process, what happens is that flow into the vessel decreases and excess pressure evacuates through the out flow.
Summary
If your process utilizes a pneumatic actuator and a new unit needs to be purchased, be sure to procure a pneumatic actuator that is compatible with current operations. The best way to accomplish this this is by working one-on-one with a reputable manufacturer. This will not only ensure you purchase the right pneumatic actuator for the job but also prevent potential problems from arising sometime in the future such as downtime.
