Uptime Magazine - October/November 2008 - (Page 48)

motor testing upload Reliability, Maintenance, Energy, Environment Considerations in Electric Motor Repair vs. Replace Decisions by Howard W. Penrose, PhD T he concept of Reliability, Maintenance, Energy, and Environment (RME&E™) was developed in the mid 1980s and evolved in the 1990s in a series of programs designed to link production, reliability, energy, waste stream, and environmental impact. The principles reside in the fact that changes in each topic impact each of the other topics to some degree. Through an understanding of these relationships, one can determine how any change can impact a significant portion of the business, either positively and negatively. In these days of renewed interest in energy conservation and environmental consciousness, we ask ourselves what we can do to have an impact. The work behind RME&E led to the understanding that the Reliability and Maintenance (R&M) function can have the single most significant and cost effective impact on energy and environment, and that each of these efforts is directly related to each other, in addition to their individual impact on capacity and productivity. Through this article, we will introduce you to some of the concepts within RME&E and how they can be used as business decision tools even in something as mundane as motor repair versus replace decisions. The US Department of Energy (US DOE), and independent researchers, have identified the potential energy cost reduction of at least 14% when a properly implemented condition-based maintenance program is put into place over a primarily reactive program. Note that just because equipment is greased, or data is taken for predictive maintenance, if there is no action, the program is reactive. This is in addition to the maintenance cost improvement of 33% of the comparison between condition based and reactive programs, and the potential capacity improvements of 25% on average. The relation is interactive, so changes made to each of the elements impact all of the other elements. For instance, if it is determined that compressed air pressure can be dropped in order to reduce air leaks and generally reduce energy, what is the impact on the rest of the system? It may actually improve the system and have a positive impact on production and reliability, or it may have the opposite effect. The results provide the business information necessary to make a positive decision including the benefit of reducing the compressors’ carbon footprint as energy can be directly converted to CO2 and other emissions. The carbon footprint reduction is converted to the equivalent energy required to produce the electricity, steam, or other forms of energy. For instance, the relationship of 0.606 tons of CO2 per MWh of electricity is related back to the generation of power and the associated emissions. The US DOE and US Environmental Protection Agency (EPA) publish tables that relate this reduction, based upon region of the country, in order to provide a more accurate comparison. The Case Study For the purpose of this case study, we will use a 250 horsepower, 1800 RPM, 96.1 percent efficient motor operating 6,000 hours per year at a 75% constant load. The energy cost will be estimated at $0.08/kWh and we will use the USA national average of 0.606 tons of CO2 per MWh (Mega-Watt hour). We will assume the motor has been operating for some time and then has a winding failure. The decision is now whether to use a low-cost repair shop that operates without a uniform quality control program or a higher-cost repair shop that includes a uniform quality control program and a motor repair specification is provided. In both cases, we will use the results of the Canadian Electrical Association 1994 independent study on motor repair, as well as the 1991 through 1993 BC Hydro and Ontario Hydro studies to demonstrate the difference between the impact of a quality repair and the low-cost repair. In the actual studies that were presented in the Uptime articles on motor repair earlier this year, the average was 1.1% reduction in efficiency per repair. For this article, we are going to round that to 1% for ease of demonstration, for a low-cost shop, and 0% reduction for the quality repair shop. The rewind cost is considered to be $1,950 for the low-cost shop and $2,825 for the quality repair shop. Based upon experience, we will assume that the quality repair survives intact over a ten year period before bearing replacement is required and that the lowercost repair is rewound two additional times, one after four years and one after three years, by the same facility. The first step is to calculate the impact of the changes to efficiency in which the quality repair is as- 48 october/november 2008

Table of Contents Feed for the Digital Edition of Uptime Magazine - October/November 2008

Uptime Magazine - October/November 2008 Contents Upfront Upclose: An Asset Management Oasis in the Desert Information Technology: Streamlining Through Simplicity Lubrication: Phases for Framing a Solid Foundation Infrared: Do Your Homework Before You Buy Maintenance Management: Get It Together by Getting Together Motor Testing: Key Elements in Motor Decision Making Precision Maintenance: Shedding Some Light on Tolerances Reliability: RCM & the Mortgage Meltdown Ultrasound: A Multidimensional Tool Vibration: The Whirling Pump Mystery, Solved with ODS Upgrade: Are You Looking in the Right Place for Your Wear Debris?

Uptime Magazine - October/November 2008

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