Selecting a new air pump to install in your shop is no small decision. Industrial air compressors are major investments and making the wrong decision can be costly in the long-run. The right compressor will efficiently meet the needs of your business without forcing you to spend more than is necessary on initial purchase, installation, or long-term operation. There are many considerations to take into account before you make your decision, so having a solid grasp of the fundamentals is a necessary first step.

Determine Your Needs

Is this the first compressor that you will be installing in your shop? If not, are you replacing an existing unit that has failed or that no longer meets your needs, or is this an additional unit that will supplement your existing compressors? Whatever the case, it is important that you take a detailed accounting of the overall demands that your shop will place on the equipment.

The first step is to determine the total cubic feet per minute (cfm) of air required by the tools or machinery in your shop that will be driven by the compressor. Once you have this number, you can narrow your requirements by evaluating the maximum load on the compressor at one time. You want to avoid choosing an undersized compressor, so it pays to be generous in your estimation and base it on the worst-case scenario for usage. Once you have this number, it will pay to add a 15-20% margin just to stay on the safe side.

Consider Power vs. Capacity vs. Pressure

Air compressors are rated with a dizzying array of specifications, many of which can be hard to understand if you are not intimately familiar with how they operate. The basic specifications to consider are generally the power output of the motor (measured in horsepower) and the output capacity (measured in cubic feet per minute, or cfm). The output capacity is the maximum amount of air that the compressor is able to push and this is the key value to look at to determine if a compressor is able to meet the demands of your shop. If a compressor cannot output enough air to run your equipment, it will not be suitable for your needs.

Less commonly considered but equally important is the amount of pressure the compressor produces. This is rated in pounds per square inch gauge (PSIG). The capacity rating is in fact somewhat dependent on this, as a compressor's capacity is the amount of air that it pushes at a specific pressure. In other words, a compressor which produces 90 PSIG of pressure and outputs 250 CFM is pushing 250 CFM of air at 90 PSIG pressure. Your shop equipment will have a minimum amount of pressure that is required to operate, so it is vital that you choose a compressor sufficient to meet this need.

So, where does horsepower fit into the equation? The purpose of a compressor is to pressurize air, so the power of the motor is being used to this end. As a general rule of thumb, more power is not actually better. Instead, consider power as a rating of a compressor's efficiency. If two compressors output the same amount of air at the same pressure, the one with the smaller engine is operating more efficiently since less power is being used to produce the same result.

Consider Tank Size and Duty Cycle

While pressure, capacity, and power take center stage, tank size and duty cycle are worth considering as well. Put simply, these two specifications will determine how long your compressor can run under heavy load. Tank size is, unsurprisingly, the amount of air that the compressor can store at one time. The larger the tank size, the longer you will be able to supply air to your equipment without requiring the compressor to run its motor. Meanwhile, duty cycle is the amount of time that the motor can run before needing to shut down.

Choosing a compressor with a tank size and duty cycle that suits your usage can be a somewhat more complex process. Larger tanks can obviously run for longer, but generally cost more and will occupy a greater amount of shop space. Likewise, more efficient pumps with smaller engines can potentially save you operating costs in the long run, but they may also have shorter duty cycles. Ultimately, you will want to carefully examine your normal operations to make a proper decision. If you expect significant periods of high loads, then tank size should be a priority. If, on the other hand, your compressor will see only light duty, then a smaller tank or a pump with a shorter duty cycle may not negatively impact you at all. 

Contact a service, like Compressed Air Systems, for more help.