Tech Tips

Air Consumption when operating an abrasive blast cabinet or air tools.

When purchasing an air compressor, allow for later growth, additional air equipment and for "pressure drop" through your air hoses and lines. We normally recommend twice as much capacity as your present requirements. However, if you have a limited budget, you can add another compressor at a later date.

When abrasive blasting within a cabinet, the air requirement of the nozzle or air jet is given in CFM. However, as blasting uses a continual supply of air, you should either have twice the recommended amount of air or plan on blasting on an intermittent basis. If your compressor runs more than 2/3 of the time, it is being overworked and will overheat and break down. A compressor should NEVER run on a continual basis.

In addition, the abrasive stream rapidly enlarges the orifice size of the nozzle. In 4-8 hours, this nozzle will wear to the next size, requiring even more air, increasing the overload on your air compressor. The compressor runs harder and gets hotter as this load increases.

All air contains a certain amount of relative humidity. In coastal locations or on high humidity days, this humidity is excessive. The temperature of the air is increased as it is compressed. If a compressor is running hard (continually running, without recycling or resting), the air temperature will become excessive, leading to the compressor tank becoming very hot to the touch. This results in a breakdown of the oil, with a resulting loss of efficiency. The only answer is to allow the compressor to "rest" until it cools down.

When running at high temperatures, as the moist air is compressed and heated, it transforms into a "vapor". This vapor-laden air will easily pass through most water separators, eventually condensing in the bottom of the abrasive blast cabinet funnel or power gun where it is combined with the abrasive. (Clogging results.) Also, as the nozzle orifice size increases in size (gets larger) through wear, the compressor works harder, puts out more moisture and the pressure starts dropping because the compressor cannot keep up with the increased load.

In summary, for satisfactory operation when cabinet blasting or using any air tool requiring large amounts of air, please observe the following recommendations:

1. Change nozzles frequently: Consider going to a smaller size to save air, or using a long-wearing Carbide Nozzle which will maintain its orifice size for a longer period of time.

2. Do not blast continually. Take a break every 5 minutes to allow air compressor to cool.

3. If air compressor tank feels hot (warm is normal), and is running continually, stop operating the cabinet or air tool and allow compressor to cool. Otherwise, compressor will overheat and eventually break down. Compressors are not guaranteed against this condition.

4. Compressor must recycle normally on and off and run no more than 2/3 the time. No air compressor is designed for continual operation. Know the capacity of your compressor and the amount of air required for your air tools, and allow a 50% overload factor for best results. (Example: Tool requires 10 CFM air. You need 15 CFM as an overload factor.)

5.Use a minimum 3/8" ID air hose up to 25 ft, from air compressor to cabinet and remember to consider air pressure drop as illustrated in table below. Example: If using 25 feet of 1/4" ID air hose, at 60 lbs pressure, you will experience a pressure drop of 19 lbs, meaning you actually have 41 lbs working pressure.

Metal piping is always preferred to air hose, as it allows the moisture-laden air to condense in the piping, where it can be removed later with the water separators. See Air Line Hookup - Metal Piping Information and Diagram.

6. Keep abrasive and dust away from the air compressor. Observe maximum air pressure requirements for abrasive blast cabinet, and either set your compressor to run within these limits or use a pressure regulator valve (air regulator), to reduce the air pressure to conform to the correct pressure requirements.

7. Always wear NIOSH/OSHA approved dust respirator and eye protection during operation, and when loading or unloading parts or abrasive. Disconnect air pressure from the unit before shutting down the unit or servicing.

8. As a general rule when cabinet blasting, use a small nozzle setup (4-8 cfm) for 3-5 HP single-stage compressors and then only plan on blasting on an intermittent basis (to allow proper cooling of the compressor). Most popular nozzle setup is medium (10-15 cfm) for larger 5 HP air compressors putting out about 15-20 CFM air. The 15-20 CFM air will keep up with the medium setup on a continual basis, but be sure to allow compressor to rest by turning off the power gun periodically. For 7-1/2 HP - 10 HP 2-stage air compressors, a large nozzle setup is recommended (20-25 cfm).

9. Use only approved Air Compressor Oil of the correct viscosity. This oil contains anti-foam agents and is especially formulated for air compressor use with rust, oil and oxidation inhibitors. Ordinary oil or automotive-type oil will break down rapidly and result in premature wear of inner parts. CHANGE OIL EVERY 100 HOURS OF OPERATION.

*NOTE - Under extreme hard usage where compressor runs hot, a higher viscosity oil is recommended.

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