03
Mar
Screw Compressors

What makes compressed air systems inefficient?

Posted on by Field Air Compressors

Having an efficient compressed air system does more than reduce energy costs, it optimises your ability to produce an output. Potential areas to assess lie beyond just the compressor itself, there are other factors to consider. Let’s explore.

1. Air intake

Air intake refers to the air drawn into the compressor. The efficiencies at this level depend on three main factors; air temperature, air composition and humidity.

1.1. Air Temperature

Cool air is more dense and compressed than hot air making more efficient to pump into the compressed air system. This is why reducing the incoming air temperature can improve the efficiency of the system. Placing inlet pipes outside the room or building, for example, is how ambient temperatures are kept at a minimum.

1.2. Air Composition

Intake air that is clean flows through the system easier than air that contains dirt, dust or other impurities. Air containing impurities causes build up on internal components and reduce compression efficiency. The effect will be decreased mass flow, reduced compressor discharge pressure, reduced horsepower, and higher-than-normal compressor temperatures. It is advised that the location of the entry to the inlet pipe should be as free as possible from ambient contaminants, such as rain, dirt, and discharge from a cooling tower.

1.3. Humidity

The higher the humidity, the more moisture there will be in the system during compression. Excessive moisture can cause rust on internal components leading to wear and tear, air leaks, and reduced storage capacity. This is why one of the best ways to protect your investment is to ensure that the incoming air is as cool and dry as possible.

2. Pressure Drops

A pressure drop can be described as a reduction in air pressure from the compressor discharge to the point-of-use. Pressure drops can happen for a number of reasons and can cause the compressor to use more energy to stabilise the pressure;

2.1. Demand Side

In a distribution system, the highest pressure drops are usually found at points-of-use. This could be because of;

  • Undersized hoses
  • Leaking hoses
  • Tubes
  • Poorly designed airline
  • Disconnects
  • Filters
  • Regulators
  • Lubricators (FRLs) 

2.2. Supply Side

On the supply side of the system, these are the main items that could be causing significant pressure drops:

  • Air/oil separators
  • Cyclonic separators
  • Dryers
  • Line Filters
  • Air Intake Filters

Minimising pressure drop requires a systems approach in design and maintenance of the system. Air treatment components such as aftercoolers, separators, dryers, and filters, should be selected with the lowest possible pressure drop at specified maximum operating conditions. Recommended maintenance procedures should also always be followed and documented.

3. System Design

Design flaws in the air delivery system can significantly impact your compressors efficiency. This could include an improperly sized distribution system, unnecessary bends in the pipes, and unfixed leaks. For instance, when compressed air moves through your piping system, friction with the pipe causes it to lose pressure (kpa or bar) as it travels. The smaller the pipe, and the longer the distance the air travels, the more friction it experiences and the more it slows down. That translates to greater pressure drop. Pressure drop also increases with every bend, join and coupling in your piping system. When you are pushing air through too-small pipes with many bends and couplings, you can experience a significant loss of pressure between the air compressor and the ends of the lines.

4. Air Compressor

When air compressors are mismatched to the application, the compressor’s efficiency and overall performance are significantly reduced.

4.1. Undersized Compressor

When the demand exceeds the supply then the compressor will be forced to operate in an unsustainable way. This can result in unexpected pressure drops and an inability to complete tasks.

4.2. Oversized Compressor

An oversized compressor is one that is more likely to start and stop. This is because the compressor will start to meet demand and then stop once the demand is met. This will lead to huge energy bills, largely caused by the spike in energy produced when the compressor starts up. The excessive start/stop cycle can also result in motor burnout, future mechanical problems and potential failure of the compressor.

5. Maintenance

Perhaps the best way to increase your energy efficiency is to perform regular compressor checks and maintenance. Regular servicing helps keep every part of your compressor in order and notice minor issues before they become larger ones. When properly maintained, an air compressor generally operates as intended and performance problems would be generally minimal.

Conclusion

By making the right adjustments to your compressed air system, you can save significant amounts of energy and money. An air compressor expert can help you assess your compressed air system and ensure that it is operating in a manner that is both efficient and sustainable.

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