Equate Motor Defects to Profitability, GHG Impact

One of the reasons that most condition-based maintenance and physical-asset management programs do not survive is that we do not tie them to business items understood at the corporate leadership level. We know now that we can correlate a successful program with safety.

But that is still a difficult barrier, especially when some safety professionals reject the concept, even though it has been accepted by OSHA through the OSHA Alliance with the Society for Maintenance and Reliability Professionals, Atlanta (smrp.org).

We can instead tie other P&L (profit and loss) areas directly to the success of a program. It is important to remember that cost avoidance is not a P&L line item, but production throughput, waste stream, energy, and greenhouse-gas (GHG) emissions are areas that tie nicely and have a direct, measurable impact on corporate profit and awareness. With newer technologies, such as advanced electrical signature analysis (AESA), torque and kilowatt fault frequencies can be used to calculate all the way down to energy loss for electrical and mechanical defects in the incoming power, motor, and driven equipment. If you do not have access to these technologies, then larger defects can be measured with a power analyzer (or even some newer relay devices) before and after correction, when you can verify the load is the same.

How much of an impact does this have?  The following example is a constant-load application, but this can be applied to variable loads with a little more work. The example is a 600-hp, 480-V motor and pump application on a variable-frequency
drive where early bearing defects and an impeller defect were found using an EMPATH AESA tester. At the operating frequency, the motor output was 114.5 kW, which was determined to be the average load over the year. At $10/kW demand, $0.10/kWh usage, and 6,000 hours annual operating time, the energy cost is calculated as:

114.5kW x $10/kW x 12 months = $13,740 demand

114.5kW x $0.10/kWh x 6,000 hr. = $68,700 usage

Total = demand + usage = $82,440 electric

GHG CO₂ = 0.1145 MW x 6,000 hr. x 0.909 ton CO₂/MWh = 624.5 ton CO₂

The motor bearing defect losses were: cage = 0.25kW; ball = 0.58kW; and inner race = 0.44kW, which calculates as 1.27 kW loss and $975/year electrical. The pump impeller defects were determined to be 1.32 kW and 2.9 kW for 4.22 kW and an energy cost of $3,039/year for a total defect loss of $3,954 and 5.49 kW loss, which is 4.8% of the total motor load and ~30 ton CO₂/year. When repaired, additional smaller defects resulted in a 7.6 kW total improvement which resulted in a system efficiency improvement of 6.6%, measured energy cost improvement of $5,472, and GHG reduction of 41.5 ton CO₂/year, which can be confirmed on the corporate energy bill. EP

For more information, contact Howard W. Penrose, PhD, CMRP, MotorDoc LLC, at hpenrose@motordocllc.com.