Troubleshooting a Compressed Air Dryer for Malfunction or Failure

Compressed air applications range from shop air to, to instrument air, to breathing air with a wide range of applications in between. There is not a best compressed air dryer type. There is only the best type of dryer for the application. The application ultimately determines the type of air treatment required. So when anyone asks me what the number one troubleshooting tip is for a compressed air dryer, my answer is always the same, “Select the right compressed air treatment equipment for the application at the outset.”

A refrigerated dryer is a poor choice if it's to be installed outdoors and subjected to low ambient temperatures. A heatless regenerative dryer is a poor choice for an air system used to blow dust off the floor. And a deliquescent type dryer is a poor selection for a pharmaceutical company needing instrument quality air. Remember, choosing a compressed air dryer wisely prevents long term maintenance and performance headaches. If you choose the right type of dryer at the outset, often no troubleshooting is required.

But as we all know, blankety-blank sometimes happens, even when considerable time and effort has gone into the process of dryer selection. Yes, compressed air dryers do break and need parts or service. Many times problems with air dryer performance derive from some other problem in the compressed air system, rather than direct failure of the dryer itself.

High Inlet Air Temperature

Most compressed air dryers are designed to operate with at a 100⁰F compressed air inlet temperature. Any departure from this operating temperature will have a dramatic effect on an air dryer's performance. Many air compressors have an integral cooler. But often these coolers will not lower the compressed air temperature to 100⁰F. I often recommend the use of a secondary "trim" cooler upstream of any dryer. Remember this: every 20⁰F degrees the amount of water in a compressed air system doubles. In other words, excessively hot compressed air holds a lot of moisture and can overwhelm a dryer.

Drain Failure

A common phrase here at Van Air is death by drowning. A typical compressed air dryer system will produce 10 gallons of water per day per 100 SCFM. So installation of dependable condensate drain valves is not a luxury, but a necessity. 80% of this moisture is removed at the moisture separator installed after the air cooled after-cooler.

A drain valve failure here guarantees that the compressed air dryer will be flooded and that liquid water will be pushed further downstream with, of course, disastrous consequences for valves, air tools and processes. It is always baffling to me when a customer spends thousands of dollars on a compressed air dryer but then selects the most inexpensive condensate drain valve on the market. Penny wise, pound foolish as they say.

Don't view drains as an expense. View them as an investment, as insurance that protects your dryer and downstream equipment.

Filter Maintenance

Coalescing and particulate filters protect an air dryer. If the air dryer is malfunctioning, regardless of what type it may be, often the root causes is a failed or bypassed coalescing pre-filter. Replace filter elements on a regular schedule. Do not depend exclusively on differential pressure indicators or gauges for determining when to chance elements. A failed filter element will register no differential pressure!

It is not uncommon to hear a customer say that that the filter element hasn’t been replaced in several years. So many times the end result is very similar to not having a filter installed in the first place. Oil and particulate clog air lines, damage air operated equipment, contaminate desiccant beds and increase pressure drop in the compressed air system. All of these things decrease the compressed air dryer performance and increase the cost of operating a compressed air system.

So pay attention to these areas, and you'll avoid lots of trouble with air dryers: good cooling, well operating drains, continuously serviced filters.

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