Maintenance Tips for Compressed Air Systems

With summer approaching it’s a good time to check your compressed air system.  Some much needed maintenance prior to summer heat and humidity will keep the air system running well.

The best place to start is at the compressor or compressors.  Start your inspection by checking the suction filters for any tears, bypassed seals, excessive dirt and back pressure. Change or clean these filters as required.

Next check that the compressor is properly cooled and there are no blockages or excessive dirt on heat transfer surfaces.  Automated louvers should be checked and adjusted.  Clean coolers and inlet filter mats where applicable.   If the compressor is water cooled, make sure the heat exchanger is clean and there are no restrictions in water flow.  Verify your cooling water cleanliness, pressure and temperature.

Check oil levels and service with an oil change or by adding oil as required per the recommendations of the compressor manufacturer.

If the compressor’s load hours to service intervals indicate too much idling, consider adjusting the sequencing controls per the manufacturer's recommendations.

Once the compressor system is fully serviced and verified to be operating at the proper temperature and pressure, it is time to check the treatment and distribution systems.

Walk around the plant and listen for leaks in piping, fittings, and air operated equipment.  Better yet, purchase an ultrasonic leak detector and find all the sub-audible leaks too.  Repair all leaks.

Check all receiver tanks for operational relief valves and automatic drains.  Pay special attention to the drain on the receiver tank between the compressor and the dryer.  This is called the wet receiver, and it will see the highest volume of condensate.  Be sure that this drain in excellent repair.  If you’re depending on manual drains to remove condensate, switch to automated drains.

Also inspect drains on separators, drop legs, and dryers.  Repair and replace as necessary.

A little bit of compressor lubricant is normal in the condensate being drained from the wet receiver, separator, and coalescing filter.  But if there is a substantial amount of oil, there’s likely a problem with the compressor, such as a failed air-oil separator.  Consult your compressor supplier for assistance fixing the problem.

Next service the air treatment equipment – the filters and dryer.

Coalescing filters can have trace oil in the drain condensate with no ill system effects.  A flooded coalescing filter can indicate a failed automatic drain either at the filter or upstream.

Check pressure differential across filters when flowing near or at capacity.  If the differential is more than 5 PSID across a filter, it’s time to replace the elements.    Watch out for zero pressure differential, as you might have a torn or ruptured filter element.  Replace as necessary.

For deliquescent dryers, be sure to check the desiccant level and add tablets as necessary. Safely isolate and depressurize the vessel before opening the filler hatch.  Also replace the hatch gasket during every service interval.

If you have a refrigerated dryer, check that the condenser is clean.  Never situate the dryer against a wall such that air flow across a condenser is restricted.  Check for pressure drop across the evaporator.  If it is high you will need to verify capacity and cleanliness. Check that the evaporator temperature is within specification. If not you will need to have the system serviced by a qualified refrigeration service technician.

In the case of dual tower regenerative dryers, check the outlet moisture content.  Many dryers include a color changing indicator, where blue means dry and pink means wet.  Hygrometers are even better instruments for verifying dryer performance.  Remember that hygrometers need periodic sensor recalibration.  If you find the color change indicator is pink or the hygrometer indicates high dew point, verify the dryer is switching properly, that the purge setting is correct, and that there is no oil or liquid water present at the purge exhaust.   If the purge exhaust mufflers are oily to the touch, you’ve likely got a problem.  If you suspect oil contamination of a desiccant bed, block the dryer in, verify it is fully depressurized, and obtain several desiccant samples from as deep in the bed as possible.  If the desiccant is tan or brown, it needs replacing.

Always verify that your dryer is operating within its design conditions with respect to temperature, pressure and flow capacity.  Most dryers are designed for 100⁰F inlet compressed air.  Performance of the dryer will degrade as the inlet temperature rises.  If the dryer is not performing and everything appears to be functioning properly, the desiccant is in good condition and there are no alarm conditions, you’ll need to consult a qualified service technician or call the dryer manufacturer for support.

Once you have walked the entire system and are satisfied everything is functioning satisfactorily it is a good time to set up your next preventative maintenance in your schedule. Be prepared for unexpected problems and avoid expensive down time by ordering high fail and wear parts to stock in your maintenance department. Items such as filter elements, spare desiccant, and spare drain valves are critical. Spare switching valves, check valves, and block and bypass valve repair kits, component seal kits, hatch covers and instruments are often overlooked items.

As always, call (814-774-2631) or email (info@vanairsystems.com) Van Air Systems if we can be of support.