Pressure problems are one of the most common air compressor issues we get asked about. The air compressor is running, but there simply isn’t enough pressure to run your tools and equipment. What’s the deal? There are several potential issues that can cause problems with inadequate pressure including pressure drop in your compressed air system. In most cases, the issue is not with the compressor itself, but somewhere in the distribution system — and the fix may be an easy one.
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How Much Pressure Do You Need?
Pressure in a compressed air system is measured in Pounds per Square Inch, or PSI. Different tools and equipment require different PSI levels to operate effectively. Most industrial tools and equipment are optimized for pressures between 90 and 100 PSI. Some applications may require pressures between 100 and 120 PSI. For tools and equipment to work properly, the pressure at the point of use (i.e., where the tool is hooked up) must be at or above the minimum PSI rating.
Pressure drop is the difference between the PSI at the air compressor discharge and the PSI at the point of use. There is always some degree of pressure drop across the compressed air distribution system but in a well-designed distribution system, this should not exceed 3%. For example, to achieve a PSI of 90 at the point of use, you may need to set the compressor to 100 PSI. Ideally, pressure drop will be closer to 3 PSI across the system.
Note that ramping up PSI beyond the minimum level needed to run all tools and equipment usually does not provide an additional benefit and may actually be detrimental to the life of the tool. Over-pressurizing the compressed air system adds more wear and tear on the compressor and on air-powered tools and equipment. It is also a waste of energy. Pressure levels for the air compressor should be set at the lowest level needed to maintain the pressures required at the end of all pipe runs.
Read more: Reduce Plant Pressure to Save Money and Energy.
What Causes Pressure Problems in a Compressed Air System?
Often, the first instinct when experiencing problems with maintaining PSI in the system is to run out and buy a larger air compressor. But a larger compressor is not always the answer. Inadequate pressure at the point of use will usually boil down to one of two issues: a problem with the compressor itself, or a problem with the distribution system. It is important to adequately diagnose the problem in order to determine the right fix.
- Compressor problems: Can the compressor maintain adequate PSI for the airflow required to run all tools and equipment? If the compressor is not sized adequately for the PSI or airflow required, or it has a mechanical problem preventing it from reaching its rated PSI, you will not have enough pressure to run your tools and equipment.
- Distribution problems: What is the difference between the PSI of air leaving the compressor and air at the point of use (pressure drop)? If air leaving the compressor is adequately pressurized, and you have plenty of airflow, the problem most likely lies in your distribution system.
Diagnosing Air Compressor Pressure Problems
The first step in diagnosing pressure problems within the compressed air system is to check the compressor itself. Is it actually producing air at the rated pressure? You can test this by measuring the output pressure at the compressor outflow. Most industrial compressors have a built-in pressure gauge that will allow you to see the pressure it is producing. You can also use a separate pressure gauge, especially if you have reason to believe that the built-in gauge is not working correctly. Here are some simple steps for checking the pressure that your air compressor is producing.
- Locate the Pressure Gauge: Most air compressors have a built-in pressure gauge, which will allow you to see the pressure the compressor is producing. The pressure gauge is usually located on the compressor’s control panel or near the outlet.
- Start the Compressor: Turn on the air compressor and allow it to run and build up pressure. Be sure to follow the manufacturer’s instructions for safely starting the compressor.
- Monitor the Pressure Gauge: As the compressor runs, watch the pressure gauge. It should gradually increase as the compressor builds up pressure.
- Check the Pressure Reading: Once the compressor has reached its maximum pressure and the motor shuts off (this is called the “cut-out” point), check the reading on the pressure gauge. This is the pressure that your compressor is producing.
- Test with a Tool: If you want to check the pressure at the point of use (i.e., at your tool or equipment), you can attach a separate pressure gauge to the air outlet of the tool. Start the tool and check the pressure reading on this gauge. This will give you a sense of the pressure being delivered to the tool, which can be lower than the pressure in the compressor due to pressure drop in the distribution system.
Testing the PSI at various places in the system can help you pinpoint where the problem is.
- If the air coming out of the compressor is not at the required PSI, this indicates a potential problem with the compressor itself.
- If the PSI at the air compressor outlet is adequate, you can check the PSI at different points in the system to see if you are experiencing pressure drop in particular locations. See what the PSI is at the point of use for each tool or machine. Also, check the PSI before and after filters, valves, fittings, hoses and connectors and other places where an obstruction or leak may be present.
- If you are not finding a significant pressure drop within the distribution system, you can try operating your system at a lower CFM by turning off some equipment. If the compressor is able to maintain adequate PSI with lower air use, it may indicate that your air compressor is undersized for your applications.
Is Your Air Compressor Big Enough?
An important question to ask when determining the root cause of a pressure problem is whether the air compressor is sized adequately for the application. If the compressor is too small for the demand, it may not be able to generate enough pressure. This could be due to a mismatch between the compressor size and the tools or equipment being used.
An air compressor is rated for a maximum pressure (PSI) at a particular airflow (in Cubic Feet Per Minute, or CFM). For example, a rotary screw air compressor may be rated at 125 PSI for up to 75 CFM. Pressure and CFM are inversely related; if you are using more air than the compressor is rated for, it will necessarily result in a drop in pressure.
In sizing an air compressor, ask:
- What is the pressure required to power tools and equipment? What pressure will the air compressor have to produce, considering the expected pressure drop across the system?
- What is the peak CFM demand generated by all air-using tools and equipment?
If the air compressor is not keeping up with air demand, it usually indicates that it does not have a high enough CFM rating to power all your applications. The CFM rating will be directly related to the horsepower (HP) of the motor; the higher the HP, the more air the compressor can make at a given pressure.
To determine your peak demand, use our handy CFM Calculator.
If the compressor appears to be sized appropriately to meet your PSI requirements and CFM demands, the problem lies either in a mechanical issue with the compressor or a problem in the distribution system, causing excessive pressure drop.
Aire Tip: Adding additional compressed air storage can help you meet short, temporary peaks in CFM demand without increasing the size of your air compressor.
Common Causes of Pressure Drop in a Compressed Air System
In most cases, when we see problems with pressure in a compressed air system, it is not the compressor itself causing the issue, but excess pressure drop across the distribution system. This can be caused by a number of different issues. If you are seeing a difference of 10 PSI or greater between the air compressor outlet and the point of use, it’s time to take a closer look at what’s happening in the distribution system. There are several issues that can cause a loss of pressure in the distribution system, including air leaks, poor distribution system design, blocked filters, and over-reliance on hoses and quick connectors.
A well-designed compressed air distribution system minimizes pressure drop, which will save energy and money and reduce wear and tear on your compressor. The distribution system includes all of the pipes, hoses and connectors that carry air from the compressor and air receiver tanks to the point of use. With efficient distribution system design, it is possible to reduce pressure drop to about 3 PSI.
Air Leaks
Air leaks are the #1 cause of pressure drop in the average compressed air system — and they can quickly drive up operating costs for your system. Leaks can occur in various places, including pipes, hoses, fittings, and valves. Over time, even small leaks can lead to significant pressure loss and energy waste. Pinhole leaks can develop anywhere in the system, especially with older black iron pipe distribution systems. The most common culprits in any distribution system include:
- Valves, joints and connections
- Hoses and quick connectors
- Seals and gaskets
- Condensate drains
Hoses and quick connectors merit special attention, as they are one of the main causes of pressure loss in a distribution system. To determine whether this is your problem, you can measure the PSI before and after the hose or connector.
It is a good idea to conduct leak testing and repair at least once a year for your compressed air system. In many cases, you can have leaks repaired for free through incentive programs offered by your energy company.
Friction
The friction in pipes and hoses is a significant factor in the pressure drop in a compressed air system. When compressed air travels through the pipes and hoses in the system, it encounters resistance, which leads to a loss of pressure. This is known as friction loss. There are several factors that influence the degree of friction loss.
- Length of the Pipes and Hoses: The longer the pipes and hoses, the more friction the air will encounter as it travels through them, leading to a greater pressure drop.
- Diameter of the Pipes and Hoses: The smaller the diameter of the pipes and hoses, the higher the velocity of the air traveling through them. Higher air velocity leads to greater friction loss. Conversely, larger diameter pipes and hoses allow for lower air velocity and less friction loss.
- Roughness of the Pipe and Hose Walls: Rough or corroded inner walls of pipes and hoses can increase friction loss. Over time, the inner walls of pipes and hoses can become rough or corroded, increasing the resistance to airflow and leading to a greater pressure drop.
- Bends, Fittings, and Valves: Each bend, fitting, or valve that the air has to pass through adds extra resistance, increasing friction loss. Sharp bends or tees cause more friction loss than gentle curves.
- Airflow Rate (CFM): Higher airflow rates can increase the air velocity in the pipes and hoses, leading to greater friction loss.
To minimize friction loss in a compressed air system, it’s important to properly design and maintain the system. Once again, over-reliance on rubber hoses and fittings is a primary issue. Hoses tend to be both rougher and smaller in diameter than metal piping for compressed air. When air leaves the metal pipe and enters the hose, the constricted diameter and roughness of the interior will significantly impede airflow. Replacing hoses and couplers with permanent metal piping wherever possible, reducing the length of runs, and minimizing sharp turns in the distribution system will minimize pressure loss due to friction.
It is also important to properly size compressed air piping to reduce pressure drop and optimize the performance of your system. Pipes that are larger than you need will not cause any performance issues, but pipes that are too small can result in a loss of PSI across the distribution system.
Clogged Filters
Clogged filters are significant causes of pressure drop in a compressed air system. When an inline air filter becomes loaded, it takes more energy to push air through the filter, causing a decrease in pressure. You can easily check the PSI before and after the filter to determine if this is your problem. Regularly replace the filters when they become loaded to avoid this problem.
Undersized Dryers
Air dryers must also be adequately sized, or they will become a choke point in the compressed air system. Make sure your air dryers are rated for the CFM and operating pressures you require. It is often beneficial to oversize air dryers by about 50%, especially if they will be operating in a hot or humid environment. Oversizing your dryers will account for variations in operating conditions and ensure that they can keep up with your airflow at all times of the year.
Other Issues
Filters aren’t the only places where compressed air may encounter obstructions. Other places to look in your system include:
- Blockages in hoses or pipes due to corrosion, scaling or particulate
- Clogged moisture separators or oil separators
- Blocked or faulty valves
Problems with the Air Compressor
Sometimes, there is a problem in the compressor itself that causes it to struggle to maintain pressure. If the compressor is sized appropriately for the application and is still struggling to achieve the PSI it is rated for, there may be an internal problem with the compressor.
Leak in the Compressor
Just like in the distribution system, leaks can develop in the compressor itself. This could be in the compressor’s seals, fittings, valves, cooling system, or an attached air tank.
Worn Compressor Pump or Air End
Over time, the compressor air end or pump, which is responsible for pressurizing the air, can wear out. When this happens, it can’t create as much pressure as it used to.
Damaged or Worn Valves
The compressor has intake and discharge valves that control the flow of air. If these valves are damaged, worn, or clogged, they can’t operate properly, and this can affect the compressor’s ability to maintain pressure.
Inadequate Lubrication
Many compressors require lubrication to keep their moving parts operating smoothly. If the compressor is not properly lubricated, it can lead to excessive wear and tear and can negatively impact the compressor’s performance.
Incorrect Pressure Settings
If the pressure settings on the compressor are not set correctly, it may not be able to maintain the desired pressure. This could be due to a faulty pressure switch or regulator, or it may simply need to be adjusted.
Blocked Air Intake
If the compressor’s air intake is blocked or restricted, it can’t draw in enough air to maintain pressure. This could be due to a clogged air filter or other obstruction.
Worn or Damaged Belts
In belt-driven compressors, the belts can become worn or damaged over time, which can affect the compressor’s operation and its ability to maintain pressure.
Troubleshooting Pressure Problems
If your industrial air compressor is not maintaining PSI, here is a basic checklist of things you could look into.
- Review Pressure Settings: Check the pressure settings on the compressor to ensure they’re correctly set. Verify the functionality of the pressure switch and regulator.
- Check for leaks: Inspect the entire system, including the compressor, hoses, fittings, valves, and connections for signs of leaks.
- Check the compressor pump/air end: Inspect for signs of wear or damage, which might affect the compressor’s ability to pressurize air effectively.
- Inspect the valves: Check both the intake and discharge valves of the compressor for signs of damage, wear, or blockage.
- Verify Lubrication: Ensure the compressor is adequately lubricated and the lubricant (often oil) is clean and not contaminated.
- Inspect Air Intake and Filters: Ensure the compressor’s air intake is not blocked or restricted and that the air filters are clean and not clogged.
- Check Belts (if applicable): In belt-driven compressors, inspect the condition of the belts for signs of wear or damage.
- Examine the Air/Oil Separator (for oil-lubricated and rotary screw compressors): If your compressor uses oil, check the air/oil separator for clogs or damage.
- Check the Distribution System: Look for signs of pressure drop in the distribution system. This might include clogged filters, obstructions in pipes or hoses, or excessive friction due to long or narrow pipes or sharp bends.
- Verify System Demand: Ensure that the demand from your tools or equipment has not increased beyond what your compressor was designed to handle.
Having Trouble Maintaining Air Pressure?
If you’re not getting adequate pressure from your air compressor to run tools and equipment, Fluid-Aire Dynamics can help you get to the root of the problem. We can conduct a complete system audit, detect and repair leaks in your system, and help you optimize your system to make sure you’ve got the PSI and airflow you need. More often than not, that won’t involve replacing your current compressor — but if that’s what it takes, we’ve got you covered there, too. Contact us for a free system assessment.
