Compressed Air Purity Levels and Application of Dryers and Filters

In industries using compressed air, there is a requirement to ensure that the air quality meets the standard for its intended use. Compressed air usage is generally broken down into two categories, being “power” and “process”.
  • “Power” applications include such things as air tools, air cylinders, air motors and devices that require compressed air to actuate a mechanical component.
  • “Process” applications include processes where air is being mixed with, or is in direct contact with a chemical, gas or product to agitate, fluidize, convey, clean, shape or in some manner, finish the final product.

Before a dryer can be selected, the air purity requirement must be established. The “International Organization for Standardization” (ISO) has created a table for air purity levels under document 8573.1. This document defines purity levels based on particulate levels, water vapor levels and oil aerosol levels. The first reality, will be to understand that the process

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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

Desiccant Air Dryer Types, Application Considerations and Solutions

AP-100-FP-A-compressorAlthough heatless dryers are simple in design, very reliable, and generally a low maintenance machine, the high cost to produce purge air for their use is a drawback to their use. Purge consumption may actually represent a higher percentage of actual air demand, as heatless dryers on a fixed time cycle will continue to use the same volume of purge air regardless of system demand. This excess purging will result in lower dew points which are usually not a requirement. As the dryers are normally over-sized to account for peak demand, and that demand may be reduced substantially throughout the production cycle, it is beneficial to invest in the option of “Purge Economizer Control” which will maintain a constant dew point control (within 2-4ºF), and will reduce purge flow through the monitoring of the outlet dew point. Purge consumption can be reduced substantially using this optional control system,

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