The Importance of Prefilter Maintenance and Drainage

When it comes to proper desiccant dryer performance one of the most common culprits resulting in poor dew point performance, is lack of prefilter maintenance and/or faulty prefilter drain operation. Most oil coalescing prefilter elements should be replaced at 2000 hours of service. Without a disciplined PM schedule to replace these elements and to confirm proper prefilter bowl drain operation, you run the risk of contaminating the desiccant bed.

Manual drain valves on the bottom of these filters are often problematic when not drained in a timely fashion, allowing oil to re-entrain into the airstream, causing oil to enter the desiccant chamber. Float type drains (internal or external) must be checked for correct operation as they may become fouled with oil/water emulsion and fail to operate properly. Electronic solenoid auto drains complete with off/on settable timers are most favorable when used with a strainer, as they allow periodic draining to … Read the rest


Twintower Desiccant Air Dryer Sizing

Twintower Desiccant Air DryerWhen it comes to properly sizing a dryer, there are some misconceptions that often lead to incorrect, or over-sizing of a compressed air dryer.

Most people charged with the responsibility of designing the compressed air system or installation of a correctly sized air dryer, typically match the inlet capacity with the compressor maximum output.  This is especially incorrect when sizing for an air-cooled reciprocating air compressor.  Reciprocating air compressors are typically air cooled, and use pitched vanes on the pump flywheel which drive cooling air across finned cylinders to allow/assist in the air cooling and heat dissipation.  These pumps are typically designed for a maximum duty cycle of between 50 to 75%.

If the duty cycle of a compressor that produces 20 CFM is 65%, then the maximum output or constant should be based upon no greater than 13 CFM, therefore the matching dryer size would only require 13 CFM … Read the rest