Buyers Guide Autobody
Selecting the Right Air Compressor for Automotive Body Shops
Body shops rely on air for many different applications, from painting cars, and inflating tires to powering air tools such as air grinders, impact wrenches, and air drills.
Every auto shop is different, and there is no one size fits all. The best air compressor for a given body shop will largely depend on the size of the business, hours of operation, and the types of vehicles and applications.
Asking yourself these basic questions will make your search much more manageable.
1. What's your compressor's duty cycle?
Depending on the total daily amount of time you'll be using your compressor, you'll need a compressor that fits your shop's workload. Are you using your air-powered tools and equipment for just a few hours, or are these in consistent use until day's end? Choose a compressor that will match your duty cycle to supply the correct amount of pressure throughout the day.
A piston compressor is excellent for intermittent work, like in an automotive garage where a worker may be using air tools for just part of the day. In this application, a rotary screw compressor would be too large and not the optimal choice.
Rotary screw type compressors are better suited for applications with higher demand so that they can run continuously.
2. What size air compressor does my shop need?
One of the biggest challenges for a collision repair shop is to get the right sized air compressor to guarantee you always have air when you need it.
Below are some sizing questions you should ask when selecting an air compressor.
- What amount of pressure (PSI) do I need? Pressure refers to the amount of force required to do a certain amount of work at any given point in time. It is essential to understand the pressure requirements of your shop equipment in-order-to size your compressor correctly; otherwise, you will be faced with problems.
Most equipment has specific requirements for air volume and pressure. For instance, while air tools need 90 air psi to operate, tire equipment requires around 130 psi and paint guns need between 35 psi to 60 psi. It's always important to check your tool specifications for their specific requirements! A compressor must meet these requirements for the tool to work properly.
When sizing equipment, consider all the tools you are wanting to power. Determine which one requires the highest PSI. You will need a compressor that delivers pressure to match the largest demand.
Equipment with higher psi needs may require a two-stage or multi-stage compressor to boost psi output.
Use regulators to lower the air pressure to those tools that do not require higher pressure. Using too high of a pressure when not required will damage tools and waste electricity.
- What is the right airflow (CFM) for my compressor? Flow is the compressor's ability to perform a task within a given time frame continually. The amount of flow required is determined by the length of time needed to complete a given task.
The compressor will cycle off and on and refill the storage tank for the next use. Most tools or pieces of machinery will have their CFM requirements specified, so use this information to size your compressor properly.
Determine which air tool requires the highest CFM at the highest PSI. Add 50% to the required CFM for a margin of safety and look for a compressor that meets the specification. For instance, if a tool requires 5 CFM at 90 PSI, select a compressor that delivers at least 7.5 CFM at 90 PSI.
- How much horsepower do you need? The horsepower of a motor is more or less proportional to the CFM the compressor is capable of producing. Generally, the higher the horsepower, the more CFM it can put out. However, horsepower is not a good indication of your requirements. Your PSI and CFM needs should be the main deciding factor as to which compressor is right for you. As technology improves, compressor companies have engineered ways to get more CFM per horsepower. If you are upgrading to a newer compressor, you may be able to buy a smaller horsepower compressor and save yourself money both on the purchase and every month going forward with lower electricity bills.
- How big should your tank be? Tank size determines how much-pressurized air is stored and at the ready. Larger tanks require the compressor to run less to meet the minimum pressure needed in the system. Smaller tank compressors will run more as air is used to replenish the amount of pressurized air available.
Tanks can be vertical or horizontal. This doesn't affect the capabilities of the air compressor but will affect the amount of physical space they take up. Vertical tanks are preferred in smaller spaces, while horizontal tank compressors are generally fitted to larger horsepower compressors.
- What size air tank for Rotary Screw Compressor: A rule of thumb is that for fixed speed rotary screw compressors, you should purchase 4 gallons of tank per CFM of air produced by the compressor and 1 gallon per CFM for VSD compressors.
- What size air tank for Piston Air Compressor: For piston compressors, larger tanks will allow the compressor to cycle less often. A larger tank is not a replacement for a larger compressor, so if you find your piston compressor running more than 60% of the time, it's time to start looking into upgrading it.
3. What compressed air application requirements for auto body work?
It is also important to think of any special application requirements for automotive bodywork when selecting a compressor to guarantee the best results.
- Air Compressor Requirements for Automotive Painting - Water-based paints and solvent-based paints are unique and require different levels of compressed air quality.
- Water-based paint: This paint type requires clean, oil-free, dry air to achieve the best paint results without potential fish-eyes or other imperfections. Issues with the finished product can lead to additional re-work or a complete re-paint. Oil-free compressed air is recommended for water-based applications because it eliminates the risk of oil-vapor in the compressed air or oil coming into contact with the paint. Proper carbon filtration can alleviate oil contamination for shops not operating oil-free compressors, however, there is no substitute for a completely oil-free system.
- Solvent-based paints: This paint type requires clean dry air as well, but oil-free air is not a requirement. Shops should use a coalescing filter (for liquids) and a particulate filter to remove impurities from the compressed air. Contaminants will damage paint surfaces and lead to additional labor.
- Air Compressor Requirements for Sandblasting:
- Is dry air required? Depending on the orifice and media used, dry air may be critical to continued reliability of the abrasive blasting system. Moisture in the compressed air can lead to the blast media to clog the orifice and cause sputtering.
- Is breathing air required? Abrasive blasting sometimes needs a breathing hood to protect the user. It is important to recognize that Grade D Breathing air is necessary, not simply regularly compressed air. Compressed air, even filtered, is no substitute for proper breathing air.