Specifications

Air Compressor Unit Sizing Guide
Six Steps to Assist in Selecting the Right Size Compressor
In order to provide a customer with a meaningful quotation that reflects a Compressor Unit that will handle their
compressed air requirements, one must first determine what air volumes and pressures are required on site, and then
choose a Unit to suit. To follow is a 'Six Step' Method in selecting the right sized Compressor for your customer's air
requirements.
1. Separate the Equipment into two categories.
This should be based on both Continuous and Intermittent
use. Make a list of all the air tools and equipment intended for
use with the Compressor. Hand triggered tools (air impact
wrenches, nailers, etc.) are generally considered Intermittent.
Air motors or sand blasters, on the other hand, create a
steady demand on the Compressor all the while they are
operating, and can therefore be considered Continuous.
2. Determine the total CFM requirements for each
type of equipment being used.
Using 'Chart 1' on 'Page 10', list the free air consumption for
the items in each category and multiply the CFM required for
each tool by the number of similar tools to be used.
Example: If there are two different stations, each using a 5"
body sander, the total consumption would be
2 sanders x 5 CFM each = 10 CFM
3. Total the CFM for the items in both the Intermittent
and Continuous categories.
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Example:
Intermittent Use:
1/2" Impact
Body Sander
Spray Gun
Item:
Total Consumption:
CFM:
4 4
5
10
10
10
24 CFM
Qty:
1
2
1
Total:
Continuous Use:
3/32 Sand Blaster
Item:
Total Consumption:
CFM:
7 7
7 CFM
Qty:
1
Total:
4. Combine the Total Consumption for Intermittent
and Continuous Use.
For Intermittent use, the total consumption is generally
multiplied by a factor of .40 to reflect an approximate 40%
intermittent use of the various tools. Using our example in '3',
24 CFM x .40 = 9.6 CFM
For continuous use, you must use the full value of the various
tools.
The Total Consumption for the Compressor would then be as
follows:
9.6 CFM (Int.) + 7.0 CFM (Cont) = 16.6 CFM
Note: If a number of intermittent air tools are to be used
simultaneously in a continual demand situation, replace the
40% (.40) in the formula with a figure that better represents
the actual percentage of operation, ie 60% (.60) or 70% (.70).
5. Divide the ‘Total Consumption for the Compressor’
as determined in ‘4’ by .75 .
In order to allow the Compressor to cool properly, we must
allow for downtime between cycles. The dividing of the Total
Consumption by .75 allows for this.
6. Apply the total CFM requirement as calculated in '5’
to the Devair Compressor units as noted in 'Chart
2' on Page 10.
Ensure that the maximum output pressure of the Compressor
Unit is sufficient to handle any of the tools used. In an instance
where two tools are used by the same operator, but never at
the same time, list only the tool with the higher air
consumption.
Adjusting the formula to suit individual shop requirements is
reliant on a first-hand knowledge of the total shop operation. If
care is taken to include all air consuming equipment, a good
assessment of the total consumption can be made.
How do I select a Unit to suit my Customer’s needs ?
Air Compressors
Information Bulletin IFB-01
March ‘07
For Sales & Service contact:
CENTRAIR Air Systems & Supplies 705-722-5747 [e-mail] www.centrair.ca