MRO Today - The trouble with pneumatic controls

The trouble with pneumatic controls

Pneumatic temperature controls provide an economic and effective solution for most commercial applications. Precise proportional control, environmental safety, extraordinary inch pounds of torque and quiet operation are all features of pneumatic controls. So why, then, are pneumatic controls held in such low regard by our industry today? The answer is inadequate, or improper maintenance. Most problems experienced with pneumatic controls begin at the air station itself. To avoid these problems, a well-planned, well-executed maintenance schedule must be put in to action.

Pneumatic controls require a source of clean, dry, oil-free air. A “climate control” compressor, usually located in the basement mechanical room (the darkest, dankest room in the building), provides control air. You take the dirtiest air in the building into the compressor and expect the filters and driers, located at the air station to clean it up. The filters and driers are up to the task, but only if you pay attention to them. The air cleaning starts with the compressor’s intake filter. The intake filter should be inspected and cleaned once every six months, at a minimum, more frequently depending upon the environment. When was the last time you inspected yours?

On a weekly basis, the compressor’s receiver tank should be drained, as well as all filters, bowls and airlines that have drain cocks. If excessive condensation is found, draining should be done more frequently. The compressor’s crankcase oil level should also be checked weekly. One more item for once a week is the safety relief valve (SRV). These valves are put in place to protect the controls that are downstream. To check them, adjust the pressure-regulating valve up beyond the SRV’s setting to insure that it relieves the excess pressure. Do not pull the ring on the SRV to test it. This does not test the operation of the SRV, but insures that you will be standing there to pull the ring in case of over pressure!

Once a month, the discharge air filter should be checked, as well as the setting for the pressure-reducing valve. Quarterly items include changing the crankcase oil, lubricating the compressor motor and checking the compressor’s pressure switches. Bi-annually, the airlines should be checked for oil and dirt, and check the compressor belt. Annually, cartridge-type intake filters should be changed.

Most trade schools today ignore pneumatic control training, even though pneumatic controls represent more than 50 percent of today's commercially installed base. As a result, most of the younger people in the trade are ill-equipped to work on pneumatic controls. Good pneumatic training is available through reputable wholesale distributors around the country. Quality service providers invest in as much pneumatic training as possible, insuring that their staff is able to satisfy the customers’ needs.

With a well-implemented maintenance schedule at the air station, and proper installation and calibration of the controls, pneumatic controls will do the job they are designed to do for many, many years.

Contact Mark McGann at National Energy Control Corporation for more information. He can be reached at (610) 449-9800 ext. 301 or by email at .