Compressed Air System

Compressed air leak detection

Improve energy efficiency of your air compressors by locating and eliminating leaks.

By Sachin Kambli, Festo

In brief:

  • Taking baselines from new machines, returning older machines to peak condition for fresh baselines, using hardware and software products, and working with OEMs on energy efficiency can help to reduce energy costs, improve performance and achieve greater sustainability.
  • Air quality audits can identify particulates, oil or water in the compressed air, which hinders performance and reduces machine and component life expectancy.
  • A machine that remains running when no processing is being done still consumes air. This reduces energy efficiency and can be remedied by designing operating cycles that shut the air off when the machine isn’t in operation.

Compressed air-driven actuators and vacuum grippers are effective motion systems. The greatest potential for energy savings in compressed air production is leak elimination, according to “Compressed Air Systems in the European Union,” a study conducted by the Fraunhofer Institute for Systems and Innovation Research ISI in Germany (Figure 1). Every compressed air leak is an opportunity to understand the system and enable plants to achieve more sustainable energy usage.

Figure 1. Locating and eliminating leaks is the top energy-saving measure, according to the Fraunhofer Institute study.
Figure 1. Locating and eliminating leaks is the top energy-saving measure, according to the Fraunhofer Institute study.

Manufacturers have opportunities to reduce energy costs, improve performance and achieve greater sustainability by investing time or money in some actionable steps such as taking baselines from new machines, returning older machines to peak condition for fresh baselines, using hardware and software products, and working with OEMs on energy efficiency.

Machine and system level audits

Calculating the peak efficiency of a new pneumatic system can be done easily by measuring variables such as pressure profile, flow profile and timing strokes to develop a performance baseline. As the system ages, deviations in any of the profiles indicate diminished performance, which can then be investigated and rectified.

Air quality audits are essential because poor air quality often prevents achieving maximum performance and life span from pneumatic devices.

An air consumption audit is an ideal tool, however, for equipment that’s been in operation for years with no baseline documentation. Although it might not restore a system to like-new condition, it can improve its efficiency. During an audit, a pneumatic specialist uses measuring equipment and analysis software to inspect a machine in standby, off and running modes. Consumption figures for each mode are compiled and the machine is evaluated on a component-by-component basis.

The outcome of an air audit can be significant. Consider the case of a manufacturer of baby diapers that couldn’t determine the reason for a pressure drop in its production system. An air audit revealed the cause to be a clogged air filter. The replacement of a filter led to a 10% increase in system efficiency and provided an illustration of the importance of routine maintenance.

Cleaner air

Figure 2. To determine areas for potential energy savings, a machine-level audit is used to locate air leaks. The complete evaluation covers system components from fittings and quick connects to valve terminals and actuators.
Figure 2. To determine areas for potential energy savings, a machine-level audit is used to locate air leaks. The complete evaluation covers system components from fittings and quick connects to valve terminals and actuators.

Air quality audits are essential because poor air quality often prevents achieving maximum performance and life span from pneumatic devices. Particulates, oil or water in the compressed air supplied to a machine reduces machine and component life expectancy. The audit guides the efforts to improve air quality. Typically, an outside auditor is best equipped to report on air quality and can give suggestions for improvement.

Test gear

An energy monitoring system is a dedicated monitoring tool that can be left running on one machine or used as a portable tool. It enables a plant operator to do a weekly or biweekly audit by plugging a monitoring unit into a machine. Weekly input is compared to the performance baseline, and deviations are detected immediately. Some energy monitoring systems can measure performance down to the component level (Figure 2).

{pb}
Figure 3. Ultrasonic sound equipment can identify leaks, which are tagged for repair. A comprehensive report details specific leak locations, as well as components that aren’t performing at optimal levels. The audit report also includes design recommendations highlighting ways to improve process efficiency, such as changing the size of tubing or vacuum components.
Figure 3. Ultrasonic sound equipment can identify leaks, which are tagged for repair. A comprehensive report details specific leak locations, as well as components that aren’t performing at optimal levels. The audit report also includes design recommendations highlighting ways to improve process efficiency, such as changing the size of tubing or vacuum components.

Manufacturers can develop custom monitoring systems by configuring components, interfacing them with a programmable controller and writing programming code. Companies that lack the capabilities to do this in-house can use a software package. Compressed air regulators ensure that output pressure stays at or below a preset level. Flow sensors provide real-time absolute flow data, and they measure and record cumulative component and system air consumption.

Vacuum systems are prone to leakage. Plants can take advantage of vacuum component design that has an air saving function. In a traditional application, the vacuum is on when a part is picked up. There might not be any leakage, but air continues to be consumed to maintain suction-cup vacuum. But in most practical cases, even in a well-designed vacuum application, leakage occurs (Figure 3).

A vacuum generator with an air-saving function enables the part to be picked up when vacuum is achieved. Vacuum generation ceases so no additional air is consumed to maintain the vacuum. If the vacuum drops to a predetermined level, vacuum generation reactivates.

Other problems

One of the main causes of reduced energy efficiency is a machine that remains running when no processing is being done. Although the machine produces nothing, it still consumes air. This can be remedied by designing operating cycles that shut the air off when the machine isn’t in operation.

Figure 4. Electrical energy accounts for most of the pneumatic energy consumption, while 15% is related to maintenance costs, and the balance to investment costs, according to the Fraunhofer study, “Compressed Air Systems in the European Union.”
Figure 4. Electrical energy accounts for most of the pneumatic energy consumption, while 15% is related to maintenance costs, and the balance to investment costs, according to the Fraunhofer study, “Compressed Air Systems in the European Union.”

Design considerations play a role in ensuring a pneumatic system’s energy efficiency. Original equipment manufacturers (OEMs) often are asked to build an energy-efficient machine, and they’re sometimes instructed which component supplier to use, but no method for tracking energy efficiency is built into the machine.

Software tools are available to provide information about an actuator’s pressure, flow and air consumption ratings, enabling the designer to select the component best suited to give the maximum throughput and consume the least amount of air. Similar software is available for valves, pneumatic tubing and compressed air regulators.

Detecting and eliminating leaks can lead to energy savings because 79% of the cost of pneumatic systems is electrical energy, according to the Fraunhofer study (Figure 4).

Sachin Kambli is a product manager at Festo. Contact him at sachin.kambli@us.festo.com or (631) 404-3228.