Industrial Utility Efficiency    

Air Compressors

Reciprocating air compressors are designed for variable up and down duty cycle applications as the full power of the compressor is available when needed. When demand stops, a reciprocating compressor shuts off automatically to reduce consumption of power. In selected cases where the high demand for air is short term, a tank mounted system provides air flow bursts that exceed the capacity of the compressor by using stored up compressed air from the tank.
When users consider adding an oil free air compressor to their facility, there are several factors that should go into the decision to ensure it is the right equipment for the user’s operation. Some considerations and factors can include why to choose oil free to begin with; how to properly select and size the compressor; how to adjust sizing for different cooling water conditions or different ambient temperatures; and what it will take to maintain the compressor throughout its lifespan. To lay a foundation, it is important to first understand why oil free air is important, how compressed air is used and what options are on the market.
For decades, a major meat processor and packaging operation in Northern England did what many growing companies do when more compressed air is needed to meet demand: added another air compressor and then another air compressor and so on. Yet the company decided the strategy of adding equipment had run its course, especially given a positive outlook for continued growth and the need to resolve nagging issues with system downtime and compressed air quality.
There are many critical components involved in rotary screw air compressors, and the lubricant we use is of vital importance in the process.  Screw machines rely heavily on these fluids for bearing lubrication, system cleanliness, water removal, sealing, as well as heat transfer. These fluids work in a very unforgiving environment and must function well in circumstances that would normally be deemed torturous in other lubricant applications. We run it at high velocities, through scorching temperatures, while we blast it with water.
A major automotive company needed a newer and more efficient compressed air system at one of its manufacturing plants. The original system had been operating inefficiently with old equipment and controls. Faced with a major capital investment, the plant switched to a performance contracting model. 
A large manufacturer of consumer glassware products in the North East sought a solution for injecting cold compressed air into its refractory furnace. Doing so would minimize the internal corrosion thereby extending the life of the furnace lining and their annual maintenance interval. The manufacturer opted for a unique solution from Aggreko Engineering featuring a rental, oil-free rotary screw air compressor combined with a heat exchanger and chiller.  Installed in 2019, the solution is expected to save the company $9 million monthly given the ability to maintain extend furnace maintenance from one year to two years – and boost plant uptime.
When it comes to the selection of a lubricant for an air compressor application, one of the major deciding factors is the expected life of the fluid. Yet exactly how the expected life of the fluid is determined and compared, especially between manufacturers, can be confusing. Fortunately, there are tools and tests that can provide reliable predictions of performance – one of which is a Rotating Pressure Vessel Oxidation Test. Having the test performed goes a long way toward helping those responsible for air compressor performance and maintenance make an accurate comparison between the life expectancy of lubricants offered.
Among the many “systems” plant personnel are concerned with, the compressed air system often provides the biggest opportunity for improvement and overall savings. There are many manufacturers and several air compressor technologies to choose from. Reciprocating or rotary? Fixed speed or variable speed? Oil flooded or oil free? Single-stage or two-stage technology? It’s enough to make anyone want to run and hide!
Varnish is a leading cause of airend failure in oil-flooded/injected rotary-screw air compressors. The purpose of this article is not to cover every scenario conducive to varnish formation, but to point out that many factors need to be considered when it occurs, and methods are available for its detection. Ultimately, it’s up to both the oil manufacturer and maintenance professional to ensure the oil used is up to the task of resisting varnish and maximizing air compressor performance and life.   
In an ever-evolving world of regulations, requirements, and legal ramifications, it can be all too easy to want to cover all the bases by adding a wide range of industry codes and standards to any project being put out for bid. Many assume that if the purchased equipment meets all the requirements of every developed code and standard then surely it will be a reliable and safe machine to operate with the best performance and energy efficiency. However, many of these codes and standards are developed with a tremendously broad range of machinery and equipment in mind and they may not always fit well with the specific project being developed. Compliance to these codes and standards may require very costly modifications to a manufacturer’s standard product for little to no real benefit.