Sizing diesel air compressors

Knowing your application is the first step towards choosing the right diesel air compressors. Most tools and machines powered by compressed air will give you two important pieces of information: the required air pressure and air flow. The air pressure will usually be measured in PSI – pounds per square inch. Air flow is typically measured in CFM – cubic feet per minute. Each piece of equipment will have requirements for both: “3 CFM at 90 PSI,” for example. You can run multiple tools off of one diesel air compressor, too, so gather this information for every piece of equipment that will be run off the compressor.

Once you’ve gathered the requirements, add up the CFM for all the tools that will be used simultaneously. The rule of thumb is then to multiply that number by 1.5. This will give you a good margin of error and keep you from overworking your diesel air compressor.

Next, take the single highest PSI requirement from any tool, and bump that up slightly as well. If your tools require 90 PSI, buying an air compressor that provides the CFM you need at 100 PSI will make sure you always have enough pressure to run your equipment. Don’t overdo it, though: running a compressor at 120 or 150 PSI when you only need 90 is a waste of diesel fuel.

Once you have both these figures, choose a diesel air compressor than can meet the CFM and PSI requirements at the same time. Some dealers will list CFM ratings at 45 PSI, then tell you that the same compressor is capable of 90 PSI. It may be – but it might not be able to provide the same air flow at that pressure. Don’t hesitate to describe exactly what tools you’ll be running and ask the dealer point-blank if the diesel air compressors you’re considering are adequate for the job – then compare his answers to the written specs.