Evaluate compressed air system demands to find savings

Understanding the system’s needs can optimize airflow, energy consumption, and reliability.

By Vipul Mistry August 10, 2012

Air compressors significantly increase the productivity of your processing plant, but they also account for about 10% of your electrical power consumption. It’s important to formulate a compressed air strategy to ensure you are maximizing energy savings. Evaluating your usage patterns, air quality guidelines, and maintenance needs is the key to keeping your compressed air system running cost effectively. 

Determine airflow demand 

The best way to evaluate the efficiency of your compressed air system is to assess how the air is being used in your plant from the demand to supply side. Start by identifying the components in your system that consume air, for example, assembly tools and material handling products, and their airflow requirements in cubic feet per minute (cfm). It is important to take into account which compressed air consumers are running and for how long. Many applications may require compressed air to be available all the time but cycle only for a few seconds every couple of minutes.

Reduce air supply during off-peak hours 

After you take inventory of your system’s cfm requirements and frequency of use, quantify the duration of peak demand volume relative to your average consumption. Understanding the relationship between the increments of supply—that is, compressors available—and demand will help you determine if you can apply storage to your system and turn the air compressor off. Scheduling your air assets according to system demands will ensure that you have adequate airflow while minimizing your costs.

A large production facility may opt to operate multiple compressors in lieu of one larger system. This allows the plant to meet heavy demand during the first shift and shut down some of the smaller compressors during the second shift—when usage drops—to reduce energy consumption.

Variable speed drive air compressors can also help optimize efficiency and reduce the total cost of system ownership. Conventional compressors lose efficiency when they operate below 100% capacity. However, a properly sized and applied VSD compressor will maintain peak performance while supporting a broad range of flow, regardless of demand.

Consider air quality guidelines

It is common for plants to waste a significant amount of energy trying to support an excessive air quality target. Start by defining the air quality needs for each area of your system. Then, determine if there are air quality requirements dictated by external influences in the industry or market.

The U.S. Food and Drug Administration and U.S. Department of Agriculture mandate that compressed air systems used in food and beverage applications have less than 0.01 mg/m3 oil, particulate, or vapor content. You will need a Class 0 certified oil-free air compressor to meet these guidelines. However, the contaminant tolerance is less stringent for general industrial processes and may allow you to use a Class 1 or 2 compressed air system.

Selecting the right kind of compressed air dryer is critical to cost effectively maintaining the air quality required for your process. There are several types of dryer technologies available, including desiccant, refrigerated, and heat of compression (HOC) systems. Heatless, externally heated, and heated-blower purge desiccant dryers can maintain a dew point of -40 to -100 F, virtually eliminating water from the air system. Refrigerated dryers can sustain a dew point as low as 39 F, which is adequate for general industrial applications but would not be suitable for food and beverage production.

In most circumstances, an HOC dryer used in conjunction with an oil-free air compressor provides optimal air quality and dew point management for critical applications. HOC dryers use the heat of the compressor to regenerate the desiccant and remove water from the system, providing oil-free air at a fraction of the cost of traditional desiccant dryers.

Establish a maintenance schedule

Routine maintenance is essential to keeping your compressed air system running efficiently. Maintenance schedules will vary by application and the equipment used in your system, but you should define formal expectations and assign accountability for daily, weekly, and monthly inspections. Your comprehensive maintenance schedule should include a complete system assessment, equipment service, and parts replacements, according to the manufacturer’s recommendations.

It is also important to evaluate the pressure dew point—the amount of water vapor in the air—to protect the quality of the compressed air and the end product. This is a major concern for chemical, food and beverage, pharmaceutical, and paint applications where condensate can lead to spoilage, costly clean-ups, and product recalls. Water vapor can also corrode the piping, causing premature system failure and unscheduled downtime.

Conduct a compressed air leak assessment

Most facilities rely on maintenance crews to repair leaks that are loud enough to be heard and identified. This can be challenging when normal operating noises drown out the hissing sound. Some maintenance workers walk the facility during plant-wide shutdowns to check for leaks, but this can be misleading. Many compressed air consumers are isolated from the system when they are turned off.

Your routine maintenance schedule should include a compressed air leak assessment conducted by a professionally trained team. They can use ultrasonic technology to identify and quantify even very small leaks in loud environments.

The majority of compressed air systems leak up to 30%, which can run up large energy bills. A leak assessment can help you identify the cause, location, and size of the leak, and determine the best course of action to correct it. The solution may be as simple as tightening your pipe fittings, but these system improvements can add up to significant energy savings over time.

“We have done significant research on how customers address system leaks, and we discovered that companies that try to deal with leaks on their own typically have the largest amount of problems,” said Jennifer Eckert, marketing manager, Americas service solutions at Ingersoll Rand. “This makes sense when you consider that most maintenance crews are in high demand and short on time. They have to prioritize issues related to the production process and unique system equipment, and mitigating leaks falls lower on the to-do list.”

Another challenge lies in the complexity of the ultrasonic leak detection equipment. Professional audit teams have years of experience and a refined inspection process that help increase the efficiency and effectiveness of the tool. Knowing how to use the ultrasonic device is only half the battle. It is difficult to inspect the entire system if you need to stop and fix each leak along the way. Consequently, the air leak assessment becomes an exercise in finding leaks, recording their location, and fixing them at a later date. It is important to quantify the volume of the leaks and compare that data to industrial class references. Otherwise, you may not repair enough leaks to significantly improve the efficiency of your system.

Finally, companies that try to manage compressed air system leaks on their own struggle with trending and root cause analysis.

“Maintenance workers correct the leaks, but treat it like an event without reporting the issue or analyzing the cause,” Eckert said. “It is critical that companies inventory their system leaks based on type, location, and volume. This process should be repeated at least once a year to identify reoccurring issues and ensure leaks are repaired once, the right way.” 

Optimize air supply to increase energy savings

Most companies understand why it is important to increase sustainability, but they underestimate the effect their compressed air system has on their energy consumption. Now is the time to assess your plant’s compressed air system and formulate a strategy to increase its efficiency.

Start by evaluating your CFM requirements, usage patterns, and air quality guidelines to ensure key system components are sized properly and suited for your application. Then, consider adding automated controls to maintain constant pressure and increase reliability. If you can optimize the supply side of your system, you will increase energy savings, shrink your environmental footprint, and extend the life of your compressed air system. 

Vipul Mistry is product portfolio manager for Ingersoll Rand.