For those that learned how to use a slide rule, you may remember air logic or air controls. The rest of you are saying to yourselves “Air What…?” There was a time when we would provide control packages which included only air activated components such as relays, push buttons, timers, counters, indicators and any other items needed to control the logic of machine functions. We could, and did design these controls without having any electricity on the machine. Many of these machines would be very complex even to a point of being called Robots. Then along came the advent of electric programmable controllers.
I’m not here to tell you to go backwards in technology. The electrical controls of today are so much more efficient and capable with complicated detailed packages that there is a cost savings in many cases to do the same job. The lines of code or number of available relays are virtually unlimited. So adding redundancy in your logic comes, in many cases, with no additional cost. The positioning capabilities of multi axis servo controllers are all great features of the electrical controls of today.
The question is, “Is there still a place for Air Controls?”
Let’s take a closer look at a very simple motion of an actuator. A cylinder, which is extending out and then retracting or even reciprocating back and forth. The logic is simple and so be should the controls. You will need the Air Prep unit and control or main valve even if the controls are to be electric controls. So that cost is already there. You will then add a start/stop switch and the extend and retract limit switches. These three components can be air components that will provide a signal to the Control Valve. Add a few fittings and the job is done. The cost in many cases will be less than the cost of similar electrical components such as limit switches or prox. switches.
The difference is when using electric controls, besides the air needed to move the cylinder, you also have to add another control media, electricity. Unless you use 110VAC (not always the safest) you will need a power supply. You will also need to add a control box, terminal blocks and all the other items that are necessary to contain the electrical items. Running the power to the limit switches, especially on higher voltages, you may need to put the wires in conduit. These items all cost money and in many cases do not add benefit to a simple control package.
The pneumatic industry offers air components that perform almost any basic function needed in a simple control package. Push buttons, selector switches, timers, counters, indicators and limit switches just to name a few. We can sense when a cylinder reaches the end of stroke by using a sensor that monitors pressure differential or flow, and then gives us an output signal. We have very accurate adjustable timers but simple timing can be done with a flow control and volume chamber which may even be as simple as just a length of tubing.
A short simple list of advantages to using air controls:
- One control media
- Simple
- Cost effective on simple logic
- Explosion proof
- Dependable when properly designed
- Control Box may not be needed
- Power supply or transformer not needed
So next time you are in need of a simple control package or the need for explosion proof controls, give air logic some consideration. If you think there might be a need, or just not sure, give us here at FCI Automation a call and let us review the application and maybe, just maybe you will agree,” Yes, there still is a place for Air Controls”
Written by: Nelson H. Tansey PE - Account Manager FCI Automation