Intelligent Compressed Air: Maintaining an Efficient Compressor System

compressor

The electrical costs associated with generating compressed air make it the most expensive utility in any industrial facility. In order to help offset these costs, it’s imperative that the system is operating as efficiently as possible. I’d like to take a moment to walk you through some of the ways that you can work towards making your compressed air system more efficient.

The first step you should take is to identify and fix any leaks within the distribution piping. According to the Compressed Air Challenge, up to 30% of all compressed air generated is lost through leaks. This ends up accounting for nearly 10% of your overall energy costs!! To put leaks in perspective, take a look at the graphic below from the Best Practices for Compressed Air Systems handbook.

air leaks cost

Compressed air leaks don’t just waste energy, but they can also contribute to other operating losses. If enough air is lost through leaks, this can also cause a drop in system pressure. This can affect the functionality of other compressed air operated equipment and processes. This pressure drop can affect the efficiency of the equipment causing it to cycle on/off more frequently or to not work properly. This can lead to anything from rejected products to increased running time. With an increase in running time, there’s also the need for more frequent maintenance and unscheduled downtime.

You can perform a compressed air audit in your facility using an EXAIR Model 9061 Ultrasonic Leak Detector. If you’d prefer someone come in and do this for you, there are several companies that offer energy audit services where this will be a focal point of the process.

ultrasonic_2
EXAIR Ultrasonic Leak Detector

Speaking of maintenance, proper compressor maintenance is also critical to the overall efficiency of the system. Like all industrial equipment, a proper maintenance schedule is required in order to ensure things are operating at peak efficiency. Inadequate compressor maintenance can have a significant impact on energy consumption via lower compressor efficiency. A regular preventative maintenance schedule is required in order to keep things in good shape. The compressor, heat exchanger surfaces, lubricant, lubricant filter, air inlet filter, and dryer all need to be maintained. This can be done yourself or through a reputable compressor dealer. The costs associated with these services are outweighed in the improved reliability and performance of the compressor. A well-maintained system will not cause unexpected shutdowns and will also cost less to operate.

The manner in which you use your compressed air at the point of use should also be evaluated. Inefficient, homemade solutions are thought to be a cheap and quick solution. Unfortunately, the costs to supply these inefficient solutions with compressed air can quickly outweigh the costs of an engineered solution. An engineered compressed air nozzle such as EXAIR’s line of Super Air Nozzles are designed to utilize the coanda effect. Free, ambient air from the environment is entrained into the airflow along with the supplied compressed air. This maximizes the force and flow of the nozzle while keeping compressed air usage to a minimum.

Another method of making your compressed air system more efficient is actually quite simple: regulating the supply pressure. By installing pressure regulators at the point of use for each of your various point of use devices, you can reduce the consumption simply by reducing the pressure. This can’t be done for everything, but I’d be willing to bet that several tasks could be accomplished with the same level of efficiency at a reduced pressure. Most shop air runs at around 80-90 psig, but for general blowoff applications you can often get by operating at a lower pressure. Another simple, but often overlooked, method is to simply shut off the compressed air supply when not in use. If you haven’t yet performed an audit to identify compressed air leaks this is even more of a no-brainer. When operators go to lunch or during breaks, what’s stopping you from just simply turning a valve to shut off the supply of air? It seems simple and minute, but each step goes a long way towards reducing your overall air consumption and ultimately your energy costs.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

 

Image taken from the Best Practices for Compressed Air Systems Handbook, 2nd Edition

Compressor Control – A Way to Match Supply to Demand

Rarely does the compressed air demand match the supply of the compressor system. To keep the generation costs down and the system efficiency as high as possible Compressor Controls are utilized to maximize the system performance, taking into account system dynamics and storage. I will touch on several methods briefly, and leave the reader to delve deeper into any type of interest.

air compressor

  • Start/Stop – Most basic control –  to turn the compressor motor on and off, in response to a pressure signal (for reciprocating and rotary type compressors)
  • Load/Unload – Keeps the motor turning continuously, but unloads the compressor when a pressure level is achieved.  When the pressure drops to a set level, the compressor reloads (for reciprocating, rotary screw, and centrifugal type)
  • Modulating – Restricts the air coming into the compressor, as a way to reduce the compressor output to a specified minimum, at which point the compressor is unloaded (for lubricant-injected rotary screw and centrifugal)
  • Dual/Auto Dual – Dual Control has the ability to select between Start/Stop and Load /Unload control modes.  Automatic Dual Control adds the feature of an over-run timer, so that the motor is stopped after a certain period of time without a demand.
  • Variable Displacement (Slide Valve, Spiral Valve or Turn Valve) – Allows for gradual reduction of the compressor displacement while keeping the inlet pressure constant (for rotary screw)
  • Variable Displacement (Step Control Valves or Poppet Valves) – Similar effect as above, but instead of a gradual reduction, the change is step like (for lubricant injected rotary types)
  • Variable Speed – Use of a variable frequency AC drive or by switched reluctance DC drive to vary the speed of the motor turning the compressor. The speed at which the motor turns effects the output of the system.

In summary – the primary functions of the Compressor Controls are to match supply to demand, save energy, and protect the compressor (from overheating, over-pressure situations, and excessive amperage draw.) Other functions include safety (protecting the plant and personnel), and provide diagnostic information, related to maintenance and operation warnings.

If you would like to talk about compressed air or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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