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.
As readers of this publication know, there are many ways to save energy in industrial compressed air systems. One common supply side technology is the variable frequency drive (VFD) of the compressor. It is well-documented that positive-displacement compressors with VFDs provide cost-effective savings in comparison to inlet modulating, load-unload, and variable displacement control.
Quite a number of worst-case compressed air scenarios have been encountered over the years but none may compare to the conditions that existed in a metal foundry somewhere in North America. For reasons you are about to discover, we will not reveal the name of this factory or its location, in order to protect the innocent from embarrassment.
Production complains about frequent work stoppages due to air supply related problems. It wants a more reliable consistent source of compressed air. Maintenance says it will need to replace an older compressor with a new one to improve the reliability and stability of the system. Maybe purchase a bigger one than currently needed in anticipation of future increases in air demands. Management wants assurances a good return on the investment will be realized from the expenditure before making a financial commitment. For comparing and evaluating alternatives, a benchmark must be established to determine the cost to run the current system. An assessment must be performed to identify the saving’s opportunities and assign dollar values. Questions about the cost of the assessment and what is to be expected in return need to be answered.
This metal fabrication and machining facility produces high-quality precision-built products. Over the years, the plant has grown and there have been several expansions to the current location. The company currently spends $227,043 annually on energy to operate the compressed air system. This figure will increase as electric rates are raised from their current average of 9.8 cents per kWh.
EnergAir’s unrivalled expertise in compressed air management is helping to save in excess of $50,000 per year at Whirlpool Corporation’s Ottawa, Ohio production facility. Whirlpool is the largest global manufacturer of home appliances and employs almost 70,000 people in more than 60 production and technology centres around the world. The Whirlpool plant in Ottawa manufactures a market-leading range of trash compactors, chest freezers, upright freezers and refrigerators.    
Boeing Canada Winnipeg (BCW) has been recognized with the best improvement project of 2013 within the Boeing enterprise worldwide. A cross-functional project team including BCW staff, Manitoba Hydro technical support, and design engineers from Alliance Engineering Services, Inc. used innovative high-pressure storage to reduce the required size of their air compressors and save substantial utility energy and demand charges.
Most of us understand each individual has a unique DNA combination. Compressed air is very similar, each compressed air system should be uniquely designed so the system performs in harmony. Properly managing the compressed air system requires an investigative audit to understand the nuances of the system and identify the most effective solution(s) for efficiency. Not investigating the system, before selecting improvements, would be like consenting to surgery without having an exam. Yet, this frequently occurs in businesses operating compressed air systems.
This is a food processing plant where processes and standards are controlled by FDA to AIB standards. Annual plant electric costs for compressed air production, as operating today, are $116,765 per year. If the electric costs of $3,323 associated with operating ancillary equipment such as dryers are included, the total electric costs for operating the air system are $120,088 per year. These estimates are based upon a blended electric rate of $0.085/kWh.
Compressed air reliability has been the obsession of both factory personnel and service providers for a number of years now. Constant availability of high quality air can be absolutely critical to maintaining efficient plant production. Most modern factories operate reliable compressed air systems – and more recently have also begun to focus on the efficiency of those systems. The objective of this article is to use a few real-life case studies of already reliable compressed air installations to illustrate the potentially huge economic benefits of also improving system efficiency.
This paper mill currently spends $1,747,000 annually on energy to operate the compressed air system at their plant located in the southwestern region of the U.S. The set of projects recommended, in this system assessment, could reduce these energy costs by $369,000 or twenty-one percent (21%). Estimated costs for completing the projects total $767,900, representing a simple payback of 25 months. More importantly, these projects will improve productivity, quality and maintenance costs - many associated with poor compressed air quality.