Q: Can an air dryer really make
much of a difference?
A: Hot air holds
more water. Every 20° F increase in temperature doubles the amount of moisture
suspended in air. Every 20° F decrease in temperature reduces the amount of
moisture suspended in air in half. An aftercooler or air dryer can eliminate this
fluctuation. Air entering a 10hp compressor at 75° F and 75 percent relative
humidity would produce 6.3 gallons of water per day. An air-cooled aftercooler
with a separator would remove 4.3 gallons per day and a refrigerated air dryer
would remove an additional 1.7 gallons. Only .3 gallons would be left within the
50,400 cubic foot of compressed air. Q:
How much water is generated by my air system?
A: One 100 cfm
compressor operating at 100 psig will generate 18 gallons per day at 90° F
and 50 percent RH. About 60 percent of this moisture will be removed by the aftercooler.
The remainder will pass into your compressed air system if a dryer is not installed. Q:
Which filters and dryers do I need for my application in order to eliminate moisture
and contaminants in my airlines?
A: This depends on the application
and required dewpoint. For most applications, a 35° F dewpoint is sufficient,
which can be provided by a refrigerated air dryer. For outdoor applications, a
desiccant dryer will be necessary to provide a -40° F dewpoint. Filters will
provide various levels of contaminant removal and can be selected according to
the application requirements. Q: How many cubic
feet does a receiver hold?
A: Only stored air above the pressure
being used is defined as useful free air. Majority of pneumatic tools and work
processes only require 90 to 100 spi. Storing compressed air above this working
pressure provides a surplus of useful air that can accommodate work demands. A
120-gallon receiver at 175 psi stored provides 193 cubic feet of compressed air. Q:
What size piping is needed in a properly designed system to minimize pressure
drop?
A: This would depend on the capacity (CFM) of your air
compressors, the required pressure and the total length of piping in the system.
By knowing those three factors, standard tables can be used to determine the size
of pipe required to minimize pressure drop. It is also important to know the number
of valves and elbows in the system, as each one counts as an equivalent length
of straight pipe. Size piping for the maximum CFM required and include the current
system capacity and possible future expansion in your piping plan. | 
