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How to prioritize the leaks in your compressed air system using LeakQ

2020-03-30 | 工業用画像処理

There are many ways to prioritize assets when developing a proactive maintenance plan—the most common uses criticality analysis. That is, the assets with the greatest potential for impacting the bottom line are higher on the priority list, while those that have little-to-no impact are on the bottom of the list.

Fluke ii900 Sonic Industrial Imager

Since compressed air systems are integral to operation up time, they would likely be very high on the list. That means that there is a direct correlation between the compressed air system performance and the connected equipment performance. If the compressed air system is under-performing, the connected equipment will be too.

Leaks are the number one most common issue in under-performing compressed air systems (that were properly sized and installed). Monitoring the systems for leaks should be a high priority for any company that uses them in their operations. The Fluke ii900 Sonic Industrial Imager lets you see the leaks, but now you have a different prioritization issue at hand—with so many leaks, where do you start?

Access the how-to videos for LeakQ, reporting and other new features:

How LeakQ works

The physics of air flow and sound is very complex. All conversions from decibel (dB) level to flow rate are estimations, and as such have a significant level of uncertainty. While there is not a direct mathematical way to obtain a flow rate out of its sound signature, the LeakQ flow estimator might provide the best guidance. Currently in beta, the LeakQ provides an estimation for the size of each leak and these estimates will improve with future releases.

Screenshot of LeakQ from the Fluke ii900 Sonic Industrial Imager

The way LeakQ estimates is mostly empirical, based on average sound generated by average leaks. Fluke measured many leak types at different flow rates and at different pressures, then came up with a regression model to estimate a flow rate out of a dB measurement by the Fluke ii900 Sonic Industrial Imager. It is important to recognize that LeakQ does not provide flow measurements.

Comparing LeakQ to traditional methods

The sound generated by a leak, represented by its dB level, decreases exponentially with the distance to the point from which it is measured. By including a measurement estimation, the ii900 is capable of compensation for that the distance to get an estimation of the dB level generated at the point of leak. This is an advantage versus traditional ultrasonic tools that require you to:

  • Measure the dB of a leak at a certain distance, or
  • Manually correct the measurement with the distance, or
  • Assume a bigger error due to not considering the dB attenuation due to the distance.

Typical ultrasonic tools only measure the dB level on a narrow frequency band around 30kHz, 35kHz or 40kHz. The ii900 LeakQ mode performs an automatic scan in the frequency spectrum from 2 to 52kHz and captures the actual frequency range in which the leak generates most of its sound energy, obtaining a dB level for that entire range. That makes the estimations of the ii900 more representative of the real leak than those made with traditional ultrasonic tools.

Inherent limitations in leak cost estimation

In addition to the inherent uncertainty of estimating air flow based on the sound it produces, the flow rate through a leak will be variable in time. The flow depends on the system’s pressure, but also the actual pressure at the point of the leak, which depends on backpressure. This flow and pressure at the leak will vary depending on several factors, such as the load of other tools or subsystems fed on the same line. In addition, the efficiency in converting electrical kW to compressed air CFM of a given system will be a variable in time, depending on the overall load and operating point in which the compressors are working, among other factors. All those elements add variance or uncertainty in estimating the cost of a leak.

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