The answers to the most frequently asked questions.

Yes, the rule-of-of thumb is the bigger the better when it comes to air storage. Having a large volume of compressed air in reserve allows your system to 1) “ride through” peak air usage events without causing a major drop in system pressure and, 2) lowers your energy costs in allowing the compressor to operate more efficiently. Deploying 3 gallons of air storage per cfm that the compressor delivers vs the minimum 1 gallon per cfm typically recommended, represents a 15% reduction in your operating costs, on average.

Yes, an air dryer is highly recommended if you want clean, dry compressed air at your points of use. Consider that an aftercooler removes about 65% of the condensable water in compressed air. You will continue to see water in your air unless you deploy a properly sized refrigerated air dryer that removes the remaining 35% of condensable water.
For example, a 10 hp compressor operating 24/7 with air entering the system at 75 degrees and 75% relative humidity inhale atmospheric water vapor at the rate of 6.3 gallons per day. An air-cooled aftercooler with a separator would remove 4.3 gallons per day. A refrigerated air dryer would remove an additional 2 gallons for a total of 6 gallons removed. The remaining .3 gallons would exit the system in a vapor state essentially leaving your air lines devoid of liquid water.

The aftercooler and air dryer remove the moisture present in the compressed air stream. Air Dryers come in three basic technologies: refrigerated (+35˚F dew point), desiccant (to -100˚F dew point) or membrane (to -40˚F dew point).
Most facilities depend on refrigerated air dryers. Applications like spraying waterborne paints need a much lower dew point (+4˚F dew point) to achieve the 5-10% relative humidity required. Outdoor applications subject to freezing temperatures should deploy a desiccant dryer to achieve dewpoints as low as -40 degrees F. Dryer technology choice is based on the level of dryness your application requires.
Contaminant removal is accomplished with inline filtration which comes as particulate removal filters (1 to 5 micron), oil coalescing filters (0.01 micron) and, oil vapor filters (0.03 micron) that remove odors or hydrocarbon vapors.

Low oil levels can cause your air compressor to run hot as can dirty coolers or inadequate ventilation. Check the oil level as your first step and add the proper oil if low. If the over-heating is not corrected by adding oil, then focus on the cleanliness of the radiator. If the room is much hotter than the ambient air, the problem could be poor ventilation around the compressor.

Air dryers are not required but are highly recommended. They help to ensure your air system continues running at peak performance with the highest quality air downstream and the least investment in maintenance. If you use your air compressor system for auto body paint, you could experience paint spotting and rework if your air quality is poor.
Hidden costs of water in the system include rust and excessive maintenance costs and failure of pneumatically powered tools or devices. Clean, dry compressed air keeps your tools and air lines working reliably and at maximum air output. Waterborne painting applications should deploy a desiccant or membrane type dryer to achieve dewpoints as low as -40 degrees F.

Check automatic drain trap mechanisms to ensure they are working properly. Manually drain the air receiver. (Consider adding a Mattei Automatic Tank Drain for convenience). Additionally, implementing a moisture separator to the air line will reduce moisture in the future. If draining does not resolve your issue, have your air dryer serviced. If it is no longer serviceable, replace the air dryer.

Follow this checklist to rule out problems:

  • Clogged or worn filter elements
  • Holes in distribution piping
  • Leaks at the connection, valves or lines
  • Excess system pressure drop
  • Hose diameter too small for the length of the hose being used and flow required
  • Quick-disconnect bore too small for the flow required

The complete costs of and air compressor is comprised of 1) the purchase price, 2) the energy costs to operate it and 3) the maintenance and service costs.
The rule-of-thumb is the purchase price only reflects roughly 10% of the overall lifecycle cost of owning an air compressor. Maintenance costs reflect an additional 10%. Energy costs reflect the “big money” to run an air compressor as they equate to roughly 80% of the lifecycle costs. Best practices of providing adequate air storage and energy efficient inlet control schemes can have a major impact in lowering energy costs.
Consider the energy cost to run a 15 hp compressor that operates 12 hour/day, 5.5 days per week (3,432 hours/year) at a cost of 10 cent per kilowatt hour. Electricity alone costs the user $4,416.47 per year or, $368.04 per month or, $84.93 per week or, $1.29 per hour. Or, $44,165 just in electricity, over a 10-year period of ownership.