If you’re in the market for a new air compressor, you know there is a lot that goes into that decision. You have to think about your usage, tools, power availability, pressure demands, airflow needs and system controls. Then, there are additional features that can improve the results of your air compressor that you’ll need to consider. And if you’re buying used? There are even more decisions to make and questions to ask regarding its previous use.
Thankfully, we know air compressors inside and out and specialize in finding the right one for your needs. As you work through the purchasing process, there are some questions you can ask to help you buy a new or used air compressor.
What I Need to Know Before Buying a Compressor: Questions to Ask Yourself
Asking yourself several questions before selecting an air compressor will help you choose the tool that best meets your needs. It helps to have an understanding of how you’ll use the air compressor, when you’ll use it and where you’ll use it. Some questions to ask yourself include:
1. What is the Application?
You need to know what you’re going to be using the air compressor for because the use influences the type of compressor you’ll need.
For instance, the pharmaceutical or food processing industries have stricter application requirements than other industries. If your company is in the pharmaceutical or food industry, you may want to consider an oil-free air compressor, which minimizes the risk of any oil coming in contact with the air itself. When you use compressed air to remove shells from nuts or mix dry products, the food comes into direct contact with the air. Direct contact means that the air must be free of particulate contaminants and should have a low dew point, to prevent microbial growth.
Understanding air quality needs is a major component of selecting an air compressor. Identifying proper application use will also help you determine things like the duty cycle you need, the compressor design, power requirements and more.
2. What Air Tools Will You Be Using?
The tools that you plan to use with your air compressor each have a rating in cubic feet per minute (CFM). The rating tells you how much air the tool will use, and for multiple tools, you’ll need to add the ratings together. Another reason to consider your equipment is that some air compressor designs work better for different tasks than others. Tools that you use continuously, like sanders and grinders, can benefit more from a compressor that offers a constant flow, like a rotary screw compressor.
3. How Often Will You Use the Air Compressor?
Frequency of use is a major consideration when you’re purchasing a new compressor. The demands on a compressor working six to seven hours a day, five days a week, are much different than the demands on a compressor that is only used every once in a while. Try to get an idea of how often you’ll have the compressor running. You’ll also want to consider how frequently it will be turned on and off. Intermittent power puts different demands on the system than continuous use.
Knowing your usage can help you determine what duty cycle your compressor needs. The duty cycle determines how long a compressor can run at a time. If it has an 80% duty cycle, it shouldn’t be run for more than eight minutes for every 10-minute period. Industrial compressors can have a duty cycle of up to 100%, so they can run continuously, while hobby compressors may have around 50%. A higher duty cycle can offer better efficiency over higher-horsepower models, depending on the application.
4. Where Will You Store and Use the Compressor?
Location plays a significant role in the operation of your compressor and can affect air quality, maintenance factors and the office environment. If the compressor is outdoors, you’ll need to protect it from rain, heat, sunlight and other elements. Many compressors are built for this purpose and manufactured accordingly.
Ventilation is a primary concern when an air compressor is indoors. Small, enclosed spaces like closets can impede operation and generate a lot of heat. Most compressors are air-cooled, so be sure that the heat emissions from the compressor do not recirculate to the space where cooling air should be. Placing a compressor too close to the wall can also create excessive heat — aim to put it at least three feet away. The right compressor size and style can help you fit it in a good location.
Single, muti-stage and rotary screw air compressors are all stationary and designed for use in one location, while portable air compressors can provide more flexibility, as you can move them around and to your work station. You’ll still need to keep a portable air compressor well-ventilated and attach it to an appropriate power source. It is typically a good choice for one-person operations.
5. What Type of Power is Available?
Check what kind of voltage and electricity connections you have available. It may be a good idea to have an experienced electrician review your space before you buy a compressor. In a residential setting, you may only have enough voltage to power smaller, single-stage machines. Industrial environments will offer more power, but you’ll still need to know your capabilities and ensure that the device you want can match those numbers. Horsepower is generally a good indicator of how much power a machine needs, but CFM and pounds per square inch (PSI) are perhaps more useful for your calculations.
If you do not have access to electrical power, you are more limited in your choice of tool, as extension cords and generators aren’t recommended for use with an air compressor. The extension cords aren’t effective at providing appropriate power to the machine, although longer hoses can help you reach your work area better. Generators may cause fluctuations in power that can be damaging to an air compressor. A gas compressor might be a better choice if electrical power isn’t handy.
6. How Much Pressure Do You Need?
You need to know the pressure demands on your air compressor. Check manufacturer specifications to determine the PSI that your tools need and consider if they will be running concurrently. If your demand is high, a two-stage compressor might more effectively reach the PSI requirements due to its higher capacity. When choosing a machine, think about the PSI required by your highest-demand tool. If your highest-rated tool requires 80 PSI, your compressor must have a minimum of an 80 PSI rating. Remember that pressure losses can occur in your air lines and piping, especially with devices like air dryers and filters, so factor that into your calculations as well.
7. How Much Airflow Do You Need?
If you’re wondering how much airflow you need, manufacturer specifications will tell you how much air each of your tools requires, usually in CFM or SCFM. SCFM stands for standard cubic feet per minute and accounts for different environmental factors that can change the performance of an air tool. Some machines will also offer an average CFM (ACFM), based on a 25% duty cycle. To find the continuous rating for the ACFM, multiply the number by four.
Remember to add in all of the tools that are likely to be used at the same time. This compounding can significantly increase the demand placed on your compressor. Also, consider buying a machine with a little extra CFM capability if you’ll be expanding in the future or want more flexibility for heavy use times. We typically recommend a machine that offers CFMs about 30-50% higher than the requirements from your highest-rated tool.
8. What Size and Type of Air Tank Do You Need?
Air compressor tanks measure in gallons and can affect how some tools operate. Continuous-air tools such as sanders and grinders demand larger tanks than intermittent-use tools like staplers and nail guns. Bigger tanks are often better, due to less motor strain and condensation. A motor kicks on and fills up a tank with compressed air. The more it needs to turn on and off to fill the tank, the faster it will burn out, which shortens the life of your compressor. A larger tank reduces the strain on the motor by minimizing the number of starts it takes to keep the tank full.
As for the topic of moisture, air must be cooled after it is compressed. Immediately after compression, it is hot and holds onto moisture. A smaller air tank increases the likelihood of using the air before it has the chance to cool down. When warm air goes through the air lines, it can cause a buildup of condensation, which may damage the tools and the compressor itself. A large tank can help reduce these issues, and so can additional devices like aftercoolers, which cool the air before it flows through the line.
Using a vertical or horizontal air tank is generally based on personal preference and the location in which you’ll be putting the compressor.
9. What Compressor Features Might You Want to Consider?
Many facilities use additional equipment or opt for features in their compressors to meet specific needs.
- Air dryer: To address the problem of moisture in the air lines, several different types of air dryers exist to remove that moisture and reduce the dew point of the air. Some applications and sanitary work processes benefit from this kind of machine.
- Filters: The right filter system will remove moisture and particles from the air and can help you ensure a clean product. Oil and water separators can also help keep your lines clear.
- Belt drive or direct drive: In rotary screw air compressors, you can find belt-driven or direct-driven options. In a direct drive model, the motor connects to the crankshaft of the compressor. It can work at lower temperatures with high efficiencies but can be more costly, challenging to maintain and noisy. Belt-drive compressors use a belt and pulleys to connect the motor and the pump, With these models, you can adjust airflow and pressure more easily. While they may not work well in extreme temperatures or harsh environments, they are less expensive and easier to maintain.
- Cast-iron components: Cast iron crankcases, flywheels, valve seats and crankshafts can increase the durability of your compressor.
- ASME parts: Components that meet the standards and codes of the American Society of Mechanical Engineers may offer better performance and safety features.
- Low-oil protection: This feature enables a compressor to shut down if oil levels get too low, preventing downtime and expensive repairs from the effects of low fluid levels.
- Ball-valve tank drain: With this feature, you can drain the tank frequently and easily to remove any moisture.
Some of these options can be game-changers, so speak with an expert at Quincy Compressors for help finding the best features to use with your compressor.
10. What System Controls Do You Need?
System controls can modify a variety of factors in a compressor, like speed and discharge pressure, to best fit your application. They include:
- Start/stop: The simplest and most straightforward of controls, the start/stop controls turn the motor on or off depending on the discharge pressure. They work with reciprocating piston or rotary screw compressors.
- Load/unload: Also called constant speed control, this scheme keeps the motor running and unloads the compressor when it reaches a specific level of discharge pressure.
- Modulating: This type of control throttles the compressor output to reach flow requirements. It closes the inlet valve and is not very effective on displacement compressors. It is better for centrifugal and rotary screw compressors.
- Multi-step controls: Partially-loaded states allow you to control output pressure without starting and stopping or loading and unloading the compressor. A three-step compressor has options at 0%, 50% and 100% while a five-step compressor has controls at 0%, 25%, 50%, 75% and 100%.
If you’re wondering about the differences between these different types of compressors, check out our guide to how air compressors work.
What You Need to Know Before Buying a Compressor: Questions to Ask the Air Compressor Dealer
Buying a used air compressor can help you significantly save on costs without sacrificing quality. Buying a new air compressor offers a certain degree of convenience and confidence in the buying process because you know that it has not been incorrectly used or worn out after years of use. Part of the process of buying an air compressor is asking the dealer questions to learn more about the history of the equipment.
1. How Old is it?
You don’t want an air compressor that has been in use for too long, as technology has changed and improved since it was manufactured. While a used compressor can provide benefits in terms of cost, it is essential to consider how it differs from modern designs. Energy-saving designs might have been introduced that will offset the additional cost through reduced electricity bills. Or, you can use tools more efficiently to increase your productivity. Age can also affect how much stress the motor has been through, deterioration on components and other factors that may influence its performance.
Do your research on the machine itself. Some brands make compressors that last longer than others and are rated for more prolonged use. While one brand may still work perfectly after 10 years, another could struggle if it was made with cheap components or with a poor design.
2. Where Was it Used Before?
Some environments are going to break down a machine much faster than others. If an air compressor was built for indoor use but used outside, it was probably exposed to elements it was not intended to have contact with. These exposures could cause problems with it down the line.
Another consideration is compressors that are particularly delicate, or that may struggle in extreme temperatures. If you learn that a more fragile compressor was used in an uncooled facility in the Arizona desert or left in an unheated garage in the winter months up north, you may want to check out those delicate parts more thoroughly. Ensure that harsh temperatures did not harm the inner components.
3. How Was it Used Before?
In a similar vein, try to make sure the compressor was used appropriately and isn’t too worn. Like miles on a car, knowing the hours of operation can help you get a better idea of how worn the compressor could be. A compressor run for six hours a day every day will probably have more wear than one that was only run once a week for an hour.
If you understand the strain that it was put under, you may be clued into an issue such as the compressor being started and stopped more often than it should have been. This kind of activity can cause premature wear on the motor and spell trouble down the road.
4. What State Are the Filters, Tanks and Other Parts In?
This question ties into the previous one and can tell you more about how well it was maintained. Filters, tanks, exhaust and hoses should be clean and free of residue, dust or dirt. They should not be worn out or broken. If any of these issues are present, they may indicate poor maintenance practices that could spell risk in the future.
5. Can You Test it Out?
Like test driving a car, make sure that you can test out a compressor before purchasing it. Perform a thorough check on its functions and make sure all components are working properly. Testing out the equipment helps you minimize the chances of buying a compressor with a major flaw in it. You can also check that everything works according to the specifications that you need to reach.
Additional Buying Tips
There are some steps you can take to make buying an air compressor go smoothly. Aside from being prepared and identifying your unique needs, you can:
- Discuss your purchase needs with a representative who can help you find the right tool for your operation: They are experts at matching up your requirements with the right machine and are knowledgeable about different equipment.
- Consider the warranty you’re getting with the compressor: Some manufacturers or dealers will upcharge you for warranties, while others include warranties with your purchase and have extended coverage options. A warranty can save you money if an issue comes up with your compressor years after you’ve bought it.
- Have a professional electrician come in to set up the machine: Check local codes to ensure everything is within regulations.
- Understand your maintenance requirements: Ask the seller or manufacturer of the compressor for detailed information about oil and filter changes and regular cleaning procedures, to ensure your compressor lasts as long as possible and stays within warranty.
- Think about the future: Will you want to expand your system of tools or could you end up increasing their demand? It may be worth it to explore options that surpass your current needs, to open up the possibilities in the future.
Ask the Experts
Doing a bit of research before buying an air compressor helps you find one that fits your needs for air consumption, pressure requirements, location and more. The more you know about air compressors, the more likely you are to buy the right one, care for it property and maximize your return on investment.
Whether you know exactly what you need or still need some help figuring it out, the professional air experts at Quincy Compressor are ready to assist. Contact us today to learn more or find your local Quincy distributor.