Everyone who owns a car knows that neglecting preventive maintenance ultimately leads to expensive repairs. Don’t change your motor oil? You’ll eventually destroy your engine. Neglect your brakes? You’ll face expensive repairs and risk dangerous brake failure. Don’t rotate your tires? You’ll see premature tread wear and the possibility of a dangerous blow out. The list goes on and on.
Regenerative desiccant compressed air dryers also require preventive maintenance. All too often, the routine maintenance on air dryers is overlooked. Many air dryers simply run until something breaks. At this point, water, oil, or desiccant dust might have migrated downstream, causing damage to sensitive equipment, or contamination of products. Expensive dryer components might require complete replacement, such as switching valves, desiccant, and electronic components. I can’t count how many air dryers I’ve inspected where the equipment has broken due to neglect. In such a case, a customer often needs to rent expensive back-up equipment while the dryer is repaired. Simple routine maintenance prevents major expenses and downtime.
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Let’s start with the filters. The pre-filter is one of the most critical components of a regenerative desiccant dryer system. The purpose of the pre-filter is to protect the desiccant and dryer components from compressor oil, condensed water, and particulates. In the case of a heat regenerated dryer, the ingress of compressor oil could even pose a fire hazard! A differential pressure indicator or gauge shows when the filter elements need to be changed. Filter element change-outs can also be scheduled on a routine basis, usually every 6 to 12 months.
Coalesced liquids accumulate in the pre-filter sump and must be drained away, usually with an automatic drain valve. The pre-filter does no good without a properly operating drain valve. If the automatic drain is not operating – or if a manual drain is neglected – water and oil will accumulate in the filter housing and eventually spill into the dryer, contaminating the desiccant and dryer components. The drain valves must be regularly inspected and tested. Always replace or repair a defective drain. Just by maintaining a pre-filter and automatic drain valve, you will extend the life of the desiccant for years.
Every regenerative dryer must had a particulate after-filter. No exceptions. The after-filter prevents desiccant dust from migrating downstream of the dryer. As with the pre-filter, element change outs can be based on a differential pressure indicator or gauge, or scheduled every 6 to 12 months.
Regenerative dryers also have a control air filter. The control air filter protects the switching valves and solenoid valves from desiccant dust. The switching valve is normally the most expensive component on the dryer. Protecting it through regular maintenance of the control air filter is a sure investment. I suggest replacing the control air filter element whenever replacing pre-filter and after-filter elements.
Regenerative desiccant dryers use a variety of control valves to operate. These normally include an inlet switching valve, purge exhaust valves, check valves, and solenoid valves. All of these valves should be cleaned and inspected on a yearly basis. Worn or damaged parts should be replaced as needed. Repair kits are available for most of these valves. It is much less expensive to replace a few o-rings and valve seats than to replace the entire valve.
The purge adjusting valve or purge pressure setting should also be checked periodically to insure it is set correctly. The dryer manual or documentation will indicate the proper purge setting. Excessive purge amounts to wasted energy. Not enough purge will diminish the dryer’s dew point performance.
Purge exhaust mufflers reduce the noise level during depressurization and purging. Over time the mufflers will become clogged with desiccant dust. A higher than normal back pressure on the regenerating desiccant tower is an indication of clogged mufflers. If the off stream tower is showing a few pounds of pressure during regeneration, the muffler could be clogged. I suggest replacing mufflers every 6-12 months. Here’s a quick tip. If you think a dryer’s desiccant is contaminated with oil, here is a troubleshooting tip: feel the surface of the purge exhaust mufflers. If the muffler is slick the desiccant has probably been contaminated and needs to be replaced.
With proper maintenance of pre-filters, activated alumina desiccant should last up to 5 years in heatless dryers. For heat-regenerated dryers the desiccant should last 2 to 3 years. Desiccant can be visually inspected to look for discoloration and oil contamination. We also offer a free desiccant testing service. Contact me for details.
Your regenerative desiccant air dryer is designed to give you many years of trouble-free operation. A little preventive maintenance will ensure maximum life with minimum operation costs.