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How do I know if our compressor piping network is the right size?

Today’s question is an important one for anyone operating a facility that uses compressed air, such as a factory, construction site or auto body shop. If your compressor air piping sizing is not correct, there may be an excessive pressure drop between the beginning of your piping and the end of your piping—a situation that is likely to compromise the performance of your machines and tools and impact the productivity of your operations.

When there’s an excessive pressure drop in a compressor piping network the common response is to set the compressor to a higher level to bring the pressure up. Although this approach “works”, it simply masks the symptoms and is not a final solution. Operating in this manner is like driving your car with the pedal to the metal—it uses a lot more energy and lightens your wallet. What’s more, it’s not best practice from an environmental perspective.

What is an excessive pressure drop in a compressor piping network?

The rule of thumb is that the pressure at the point of use should not be more than 1.5 PSIG lower than the pressure at the compressor outlet—a 10% drop. A pressure drop greater than this means you have an issue that should be addressed.

Are there factors other than piping size that can cause a pressure drop in a compressor piping network?

Compressed air piping sizing

Yes, there are. One factor that can cause a significant pressure drop in a system is air quality. Too many impurities in the system will cause resistance to airflow. There are three contaminants that can cause a pressure drop: water vapor, oil and gas and fumes. Determining whether you have leaks in your system that are compromising air quality and thereby dropping pressure is always advisable.

What is the required pipe size for an air compressor?

There are two factors that determine the best pipe size for an air compressor:

• Distance from the compressor of the application; and

• Volume of air distributed to the end of the line.

If the machines and tools powered by the compressed air are far from the compressor you will need a different pipe size than if they are close to the air compressor. And there’s another point to consider when determining optimal piping size: whether the application is high-intensity or low-intensity.

To limit air loss in a piping network to 1 psi in a 100 psi system, the pipe needs to have a wide diameter to carry a specific flow volume a long distance. However, for that volume of air to travel a shorter distance a smaller diameter would be sufficient. The numbers need to be adjusted based on the compressor pressure and the jobs the tools are performing.

It can be hard to determine the amount of airflow that will be sent through each distribution arm of an air system because it depends on the application. For certain applications, the air could flow at a normal, even rate. This tends to be the case in large systems that consist of various legs, each of which provides air to different machines and tools. In smaller systems, a high surge will often occur, especially if the air is sent to numerous applications at once. In cases where air is sent to multiple applications from a low-capacity air compressor, the surge is often followed by a period with no flow.

Pressure loss in a piping network can be reduced with smooth bore piping made of copper, aluminum or stainless steel. These materials make it possible to use a smaller diameter pipe and maintain adequate air velocity with little pressure drop. That said, there can still be pressure loss if the piping network has sharp turns. Networks with sharp turns should be built of larger diameter pipe to avoid pressure loss.

To determine the diameter of piping for your air compressor, you must consider the maximum airflow requirements and the minimum operating pressure of your system. A study is required to calculate /your system’s maximum airflow demands. If airflow demand potentially spikes only for very brief periods, there is no need to change your facility’s piping network to meet it.

The above said, a mistake that some facility operators make is to assume that additional energy consumed by cranking up the pressure is merely collateral for the occasional high-pressure application. The truth is that the performance and lifespan of your compressed air system could be seriously compromised. The cost of upgrading your system with optimally sized piping could amount to much less than what you might pay for wasted energy and inadequate air power.


For more information about compressed air piping sizing, please contact us at CRU AIR + GAS. We would be more than happy to give you an honest, expert assessment. We’re ready to earn your trust.