In an earlier article in this e-zine I wrote about "Why use a regulator?". In this installment, the question posed is what do you do when you can't get at your pressure regulator due to it's location?
You can control a remote compressed air regulator electrically or you can control the remote regulator with an air signal, therefore, wherever the regulator is on the machine or in the building, it can be controlled from afar by an operator or a programmable logic device.
With an air piloted regulator a small "pilot" air regulator is installed in an accessible location. It's output signal is plumbed to the air-in signal port usually on the top of the remote 'main' air regulator. As the pressure from the pilot regulator is adjusted this will increase or reduce the downstream air pressure emanating from the remote main unit by increasing or decreasing the pressure on the internal diaphragm, much as if an operator were turning the adjusting screw.
A 50 PSI air pilot pressure may product a corresponding 50 PSI output on the main regulator. Correlation between the pilot and the main air regulator isn't really necessary, however. If a small air line is plumbed from a 'T' in the downstream line of the main regulator and run to a visible remote air pressure gauge located near the pilot regulator, by monitoring that remote gauge, the operator can adjust the pressure to the main regulator as needed to "dial in" the downstream pressure that is required for the application.
Another benefit of the air piloted regulator it that it can be adjusted remotely and safely for operation in explosive for flammable locations since air piloted regulators - unlike their electrical cousins - do not generate a spark when they function.
Some electric regulators may contain a simple electric motor that, when activated by an operator, will adjust the regulator to increase or decrease the downstream pressure. A remote air gauge plumbed from the downstream side of the remote unit, would be useful in providing pressure feedback information to allow the operator to adjust the downstream air pressure to the correct level for that application.
An I/P controlled regulator is another option. This type of electronic regulator will adjust the downstream pressure depending on the current that is being sent to it by the programmable logic controller on the machine. A 4 milliamp signal might correspond to 0 PSI downstream pressure and 20 milliamps might equal 100 PSI downstream pressure. A current somewhere between would adjust the pressure accordingly. If the regulator was being sent 12 milliamps, then the corresponding downstream pressure might be 50 PSI, for example.
As the application either demanded an increased or reduced pressure, a pressure sensing device at the application would read the pressure and provide the controller with the pressure information. If a change in air pressure was necessary the PLC would adjust the current to the I/P regulator to effect change, until the pressure sensor signaled the controller that the pressure level was now within the programmed pressure range.
An electronic E/P regulator works in a similar fashion to the I/P type, but the E/P style works on voltage. A 0 Volt signal might represent 0 PSI downstream pressure, while a 10 Volt signal might represent 100 PSI. As the application demanded greater or less pressure a sensing device would send the pressure level to the controller which would increase or decrease the voltage to the unit, thereby adjusting downstream pressure.
Compressed air regulators usually work best when they are installed close to the application for which they are controlling the pressure. Sometimes that means that they are located inaccessibly, or even in another building from the operator interface or control center. Air piloted and electric air regulators allow the optimal location for the main regulator, and provide convenience for the human or computer operator that has to control them from afar.
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Bill Wade's experience in compressed air and other industries spans decades; from field sales positions through to the corporate presidential office. His sales agency represents a select group of industrial firms. Mr. Wade writes about all facets of compressed air at www.about-air-compressors.com.
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