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It Pays To Fix Compressed-Air Leaks

EP Editorial Staff | October 1, 2021

Detecting and repairing leaks improves productivity, cuts energy costs, and improves overall system reliability.

By Rob Milner, Teledyne FLIR

Compressed-air systems are a critical asset in many industries. As a result, compressed-air leaks constitute a large source of wasted energy and expense, with a third of compressed air lost annually to leaks and other system inefficiencies. In many cases, the cost of the electricity to operate compressed-air systems dwarfs that for other plant systems, such as natural gas and water.

Given the necessity of compressed air, locating and eliminating system leaks can generate enormous cost savings with the added benefits of improving operational efficiency, safety, and reduced overall carbon output.

Leak Remediation

Leaks can play an outsized role in contributing to system operation problems, especially fluctuating system pressure, which can cause air tools or air-operated equipment to function at reduced capacity and efficiency, ultimately affecting production and potentially compounding issues down the line. The inefficiencies caused by unknown leaks may lead companies to purchase excess compressor capacity or even unnecessary additional compressor systems, all the while escalating costs. For existing equipment, leaks can lead to increased maintenance requirements due to unnecessary cycling and increased run time that will ultimately decrease service life.

These issues were echoed throughout a study at a chemical plant conducted by the United States Office of Energy Efficiency & Renewable Energy, Washington. The plant leadership conducted a compressed-air audit, followed by the creation of a leak-prevention program. Through the study, plant operators discovered they could significantly lower operating costs through remediation efforts. By fixing the 10 largest leaks uncovered during the audit, operators realized 70% of the overall available cost savings.

To help organizations create an effective compressed-air leak detection program that aligns with best practices and policies, plant operators can adopt ISO 50001 energy-management standards. This program provides guidance on targets and objectives to help meet the standards, including the use of data to better understand and make decisions about energy use, measure results, and review progress as part of a program to continually improve energy management.

When organizational leaders decide to implement these standards, they’re empowered to not only take meaningful steps to improve energy efficiency through compressed-air leak detection and remediation, among other key tactics, but also develop a framework that shows meaningful progress to external parties.

A United States Office of Energy Efficiency & Renewable Energy study demonstrated that fixing the 10
largest leaks in a system can achieve 70% of the overall available cost savings.

Leak-Detection Methods

Whether an organization plans to implement ISO 50001 or simply wants to improve plant efficiency for its corresponding benefits, identifying compressed-air leaks is the first step. Locating those leaks can be particularly challenging in a noisy manufacturing environment, so plant operators use a handful of methods and tools to correctly identify leaks.

High-definition acoustic images: High definition (HD) acoustic imaging, comprised of a cluster of specialized integrated microphones, is simply the fastest and usually the most accurate method for detecting compressed-air leaks. Typically, such devices feature dozens of MEMS (micro-electromechanical system) microphones, which are small, consume minimal power, and provide optimal performance and stability.

These devices can produce precise images from sounds that visually display ultrasonic information, even in loud environments with similar frequencies coming from multiple areas in the scene. The acoustic data is transposed in real-time on top of a digital camera image, which provides pinpoint accuracy of the sound source. Some tools now include the ability to automatically save images to an on-board microSD card or they are Wi-Fi enabled to send images directly to a cloud storage system for post-inspection processing, analysis, and severity evaluation.

With the ability to analyze the data, operators can easily separate sound sources and classify them manually or with the assistance of artificial intelligence developed from machine learning. Some handheld devices only require one hand to operate. Handhelds also offer the ability to quickly scan large areas from a safe distance (more than 100 meters) for safer detection and analysis, without the need to physically touch machinery or shut down production lines.

Single-microphone ultrasonic (acoustic) method: Ultrasonic (acoustic) leak detectors can detect leaks using a single microphone system operating around 40 kHz. This method relies on a process called heterodyning, which enables the operator to distinguish between leak noise and noise from the background. Heterodyning converts high-frequency noise to lower, audible frequencies, usually provided to the operator through headphones. This method, however, requires significant training to enable the operator to recognize issues based on specific sound characteristics.

A disadvantage of single-microphone ultrasonic leak detection is the operator must scan the tool back and forth over the equipment in question to locate a suspected leak. In comparison to HD acoustic imaging, this method often leads to false alarms and detection of nonexistent leaks. Most crucially, inexperienced inspectors often miss actual leaks. Finally, manually moving the microphone around equipment to locate leaks can be time-consuming and physically demanding while potentially placing the operator in danger.

Soap-bubble test method: The traditional, least expensive, and most low-tech method for leak detection is using a specialty soap solution. This requires an individual to saturate a suspected leak area with an approved soap solution. The solution will begin to bubble if a leak is present, assuming the system in question is well pressurized.

In many cases the exact leak site is unknown, potentially leading to hours of work applying the solution wherever a leak might be present—from flange connectors to packing joints or any number of common leak points. In short, soap-bubble tests can become time consuming and messy without providing any real data to confirm a given leak’s size, let alone its flow rate. The method can also place the operator in potentially precarious positions around equipment.

Of the three tools outlined, HD acoustic imaging provides the best balance of ease of use, effectiveness, and accuracy for compressed-air leak detection. It also comes with the highest upfront cost, which must be factored into whatever method, or methods, an organization chooses to invest in as part of a leak-detection and mitigation program.

Regardless of the method, preventive leak-detection measures represent a relatively fast and simple way for organizations to reduce energy consumption and enjoy the requisite cost and safety improvements without the need to completely overhaul processes and equipment. With compressed air representing one of the largest energy operating expenses for organizations, the ability to detect and eliminate leaks is crucial for creating efficient plant environments. EP

Rob Milner, PE, is the Global Business Development Manager—Condition Monitoring for Teledyne FLIR, Thousand Oaks, CA (teledyneflir.com). He has held this role for more than 20 years, developing experience in most of the company’s market verticals.

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