Industrial Utility Efficiency    

Compressor Controls

UniFirst is one of North America’s largest workwear and textile service companies. They outfit nearly two million workers in clean uniforms and protective clothing each workday. Founded in an eight-stall garage in 1936, the Company has grown to 240 customer servicing locations throughout the U.S. and Canada servicing 300,000 business customer locations. The subject of this article is an energy-saving Air Demand Analysis (ADA), conducted by Kaeser Compressors, at UniFirst’s centralized 320,000 square foot hub Distribution Center located in Owensboro, Kentucky.
“First there are the old conventions. The majority of compressor houses still employ fixed speed compressors and a cascaded pressure switch control system. This arrangement will be familiar to many, but it is outdated and inefficient, and needs to be changed. There is a comfort factor with familiar technology, which is exacerbated by constant time pressure due to other day-today responsibilities and a lack of information and good advice on what can be achieved.”  
A Tier 1 automotive plant was spending $364,259 annually on electricity to operate their compressed air system. This figure was expected to increase as electric rates were forecasted to rise from their current average of 7.16 cents per kWh. Our firm, Air Power USA, conducted a full supply and demand-side compressed air system assessment. The set of projects recommended by the assessment, would reduce these energy costs by $218,670 or 60%.
“Compressed air systems with multiple compressors operating to supply demand requirements present unique challenges in compressed air system control schemes.”
This pharmaceutical plant spends $265,100 annually on energy to operate the compressed air system at their facility. This figure will increase as electric rates are projected to be raised from their current average of 7.7 cents /kWh. The set of projects identified in the compressed air system assessment could reduce these energy costs by $139,300 per year (52%).
The $mart Sequencer® is an air compressor control system designed to reduce a plant’s energy costs by continuously monitoring system demand and automatically selecting the most energy efficient combination of available air compressors.
Compressed air system controls match the compressed air supply with system demand and are one of the most important determinants of overall system energy efficiency. This article discusses both individual compressor control and overall system control of plants with multiple compressors. Proper control is essential to efficient system operation and high performance.  
The goals of this article are to show why sequencers often have problems, and to demonstrate how avoid problems by proper system integration and controls design.
When was the last time you visited your compressor room? A week ago? Several weeks ago? If you are like many, you went in for the last scheduled maintenance interval and have rarely been back since. Air compressors, dryers and other air system components have become more reliable and self sustaining from a maintenance standpoint with each generation, requiring less and less human intervention.
The purpose of this article is to investigate the cause and effect that can occur when you reduce demand with no supply changes and the alternative which will produce positive, long term results which you can take to the bank.
Since the cost of energy has dramatically increased during the past few years, it seems that energy audit companies have opened shop on more city street corners than coffee shops in Seattle.  In addition to the mass numbers and abundant varieties of these energy savings promoters, there have been an equal number of energy audit articles written for the engineering magazines.