Air leaks are very common in compressed air systems. The key is to know how to detect and fix them as the cost of even a tiny leak adds up to a large expense if left unattended.
How common are compressed air leaks?
Compressed air leaks are widespread in all applications. Not only are they common, but they are time-consuming to find and fix. In the average manufacturing operation, 20-30% of the total energy consumption is compressed air. On average, 30% of that expense is due to compressed air leakage.
How costly are compressed air leaks?
Here are 2 examples to put your cost into perspective:
Possible Annual Cost: Let’s look at the possible annual cost for a 100,000 sq foot manufacturing facility. According to the Madison Gas and Electric, the average manufacturing facility uses 95.1 kWh of energy per square foot, per year. That means this facility would use approximately 9.51 million kWh with approximately 2.37 million kWh (25%) used for compressed air. If 30% of the air produced by this system goes to waste due to leaks, there is a waste of about 713,250 kWh per year. If they pay $0.05/kWh for energy, this plant is wasting approximately $35,600 on compressed air leakage each year! Imagine if they addressed most of those leaks and used that money to invest in their business.
In Figure 1, we show how much one specific leak could cost each year, depending on the size of the leak and the PSI that the system is running at.
Detecting your compressed air leaks
There are a few ways to identify compressed air leaks:
1. Listen – Sometimes you can walk around the plant, following the compressed air lines, and hear the hissing of a leak as you walk by it. Unfortunately, this isn’t always effective. Usually the noise of an operation makes the audible sound of a leak hard to detect or piping is usually near the ceiling and far above the floor. It is best to perform audible leak detection during the off hours or on the weekend when the plant is not in operation.
2. Ultrasonic acoustic detector – This type of detector picks up the high-frequency noise waves that a leak makes. This equipment often includes directional microphones, amplifiers, and audio filters. A visual indicator or headphones are used to see or hear leaks.
The way it works:
- When compressed air is flowing through a pipe, it is moving in a laminar flow. This type of flow means all particles are streaming in the same direction and in a parallel manner. When there is a leak in the pipe, the airflow around the leak changes to turbulent flow. The air is not moving in the same direction. See figure 2 for a visual representation.
- This turbulent air creates a noise that is interpreted by ultrasonic detectors. The detector will work in one of two ways. It will either connect to headphones and produce a sound that gets louder when a leak is present, or it will have a screen that the ultrasonic waves will show on. The wave will change a great deal when the sound gets louder.
- Ultrasonic detectors filter out background noise so that leaks can be heard or seen even in very noisy environments.
- This method is a fast and reliable way to accurately detect compressed air leaks.
How to Fix Leaks
The complexity of the leak determines how involved the repair will be. A quick fix for some leakage is to simply tighten the connections. This can save $1000s a year in electricity and takes very little time or effort. Most leak fixes are a bit more involved. These include the replacement of couplings, fittings, pipe sections, hoses, joints, drains, and traps.
How to Reduce Future Compressed Air Leakage
- Ensure that fittings, disconnects, hoses, and tubing are all high quality
- Make sure the thread sealant is properly applied
- Isolate all non-operating equipment with a valve in the distribution system
- Lower the air pressure of the system
- This is effective because the flow rate decreases when the system pressure drops. The pressure differential across a leak will be lower, so less airs leak out of the line.
- Whenever leaks are repaired, take another look at the compressor control system and adjust it accordingly. This step will ensure that the energy savings is optimized.
Compressed air leaks are a common issue but they are easy to detect and fix. It is important to routinely check for leaks and fix them immediately to prevent the costs from racking up. If you have any leak questions or general air compressor questions, please contact us.