January 28, 2008
Motor Repair and Vendor Consideration and Business Impact Part 1
By Howard W Penrose, Ph.D., CMRP
President SUCCESS by DESIGN
Member National Writers Union (UAW Local 1981) and International Federation of Journalists
MotorDoc.com
One of the more disturbing trends that have been identified over the past few years is the loss of quality control by companies dealing with repair vendors. There are any number of reasons from lowest bid awards to increased operating costs and retiring personnel and the availability of qualified personnel. In addition, some companies used to police their repair vendors by scheduling onsite witness inspections of critical repairs, until cost cutting in maintenance budgets of most companies this practice has slowed considerably. We will return to this opportunity at a later date. For now, we will discuss what you should expect through the motor repair practice. These lessons-learned can also be applied to any repair vendor or equipment vendor, as appropriate.
Having come from the repair industry, and later the test instrument industry, this trend has concerned me greatly. I have been involved in uncovering an increasing number of issues with repairs where agreements, billing, and actions do not match the service provided. It seems that then triggers the common acceptance of substandard work and/or negotiating some kind of meaningless deal, such as an ‘extended warranty.’ By the time the equipment fails again, it is either time for more negotiation or everyone has forgotten the history and the defect is repaired at the customer’s expense.
There are still a number of great repair vendors out there. When you do find one, you will want to work with them and establish a good working relationship. Expect that the initial cost may be higher than a discount shop, but you end up with high returns based upon workforce productivity, availability of equipment, and overall reduced motor repair related costs in the long run.
First, we need to dispense of one of the single most damaging urban legends to plant reliability: warranty issues will occur within the first 24 hours. If this were true, then manufacturers would only have to extend a one-day warranty versus one, two, three, five, six, or seven year warranties. In fact, the types of incipient damage to electric machines can show up seconds, minutes, hours, days, weeks, months, or even years after the equipment has been installed. Only a fraction of defective motors show signs of failure within the first 24 hours, a majority show themselves long after. To put this into perspective, the average life of an electric motor operating 6,000 hours per year, in the environment they are designed for, is 20 years (MTBF – Mean Time Between Failure) including after motor repair (assuming rewind repair).
Building upon the last editorial on greenhouse gas emissions and energy costs: we shall review an incident based upon actual events; expand them across overall impact on a company, assuming similar circumstances on all repairs; and then explore the opportunities of a proper program. In the next editorial (Part 2), we will discuss the necessary strategies and tactics to avoid the issue from the start.
In one case, there are approximately 30 fans and motors rated 200 horsepower and loaded to an average of 89%. These are 35 year old U-Frame motors with an average measured efficiency of 92.9% (measured). However, they have a failure rate of 40% over three years due to a significant overhung load problem with an average repair cost of $9,000 per motor. The motor repair vendor was brought in to provide a solution. They offered an IEEE-841 premium efficient electric motor and retrofit base for $12,000, but instead supplied U-Frame motors that cost the same amount as the premium efficient motor plus an additional cost for a retrofit base. The efficiency of the new motor was 94.5% efficient and was loaded to 93%. In addition to the same operating conditions, it was also determined that there was a severe issue with the belt tension and alignment causing a excessive loading. The difference between 89% load and 93% load was directly related to belt tension and alignment and not motor nameplate speed. The result was a series of new motors with no change to the failure rate or conditions. Assuming $0.06/kWh, a demand charge of $10/kWh, and steady operation 6,000 hours per year, what are the cost and environmental impacts of each decision?
Original motor energy and operating costs:
(200hp/0.929eff) x 0.746 kW/hp x 0.89 load factor = 143kW demand
143kW demand x 6,000 hours = 858,000 kWh
(143kW x $10/kW-month x 12 months) = $17,160
858,000 kWh x $0.06/kWh = $51,480
Total Cost of Operation = $68,640
Greenhouse Gas (CO2) each = 858MWh x 0.606Metric Tons/MWh = 520 MTons
Installed U-Frame motor energy and operating costs:
(200hp/0.945eff) x 0.746kW/hp x 0.93 load factor = 147kW demand
147kW demand x 6,000 hours = 882,000 kWh
(147kW x $10/kW-month x 12 months) = $17,640
882,000 kWh x $0.06/kWh = $52,920
Total Cost of Operation = $70,560
Greenhouse Gas (CO2) each = 882MWh x 0.606MTons/MWh = 534 MTons
Recommended IEEE-841 motor energy and operating costs:
(200hp/0.962) x 0.746kW/hp x 0.89 load factor = 138kW demand
138kW demand x 6,000 hours = 828,000 kWh
(138kW x $10/kW-month x 12 months) = $16,560
828,000 kWh x $0.06/kWh = $49,680
Total Cost of Operation = $66,240
Greenhouse Gas (CO2) each = 828MWh x 0.606MTons/MWh = 501 MTons
The differences between the original and the new motor include an increase of 14.5 Metric Tons CO2 per motor (increase of 2.7%) and an additional electrical cost of $1,920 per year, with no solution to the failure rate. If the IEEE 841 motor had been used, there would be an annual cost savings of $2,400 and a decrease of greenhouse gas emissions of 3.7%, or 18 Metric Tons, per year of CO2 with a solution to the failure rate. In either case, the vendor had sold the company on the IEEE 841 option, but delivered the U-Frame option motor instead. This would mean an increase in operating costs, an initial purchase cost and then business as usual resulting in sales for the vendor and a disadvantage to the customer. In effect, the option will cost the company: $129,600 per year in electrical cost opportunities as the original motors are phased out; will still cost $36,000 in repairs per year after the phase out; and will cost the environment 975 Metric Tons of CO2 per year; all with an investment of $48,000 per year over seven years by the customer.
If, instead, the customer worked closely with the vendor, or a different one, and identified these issues, they would have an opportunity to reduce energy costs by $72,000 per year, reduce repair costs over the seven year warranty of the motors, and reduce greenhouse gas emissions by 540 Metric Tons per year with the same investment by the company.
According to a BC Hydro study on electric motor repair in 1993, there is an average reduction of efficiency, per repair, of anywhere from 0.5 to over 3%. The over 3% issue related to some repair vendors using sealed bearings as their decision without informing the motor owner. The citation by BC Hydro was that there is an average of 1% efficiency loss per repair, which was selected as 0.5% by the US Department of Energy during the development of Motor Challenge materials and MotorMaster Plus version 1 and later, in and around 1995. This was assuming that appropriate standards were followed relating to motor repair practices.
In 1994, a joint Canadian Electrical Association study was performed on the impact of motor repair on energy efficient electric motors. The discovery was that there were material design improvements in the stator core and that following specific repair steps would reduce the impact of rewind on the motor repair. The independent study reviewed several methods of coil removal, burnout ovens using one stator at a time and temperature sensors directly on the motor core, and the Thumm Stripping Method. Stators were rewound several times each and the motors reassembled and tested at the Hydro Quebec testing laboratories in order to determine the impact of these practices on the energy efficiency of the motors. The results of the study were not widely publicized by the industry and, instead, another self-funded industry study, without independent oversight, was performed and published with results that were more favorable.
Through proper motor management practices, and oversight of vendors, a conservative average of 156 Million-MWh can be saved per year in the USA alone. This equates to an energy cost improvement of $23.4 Billion, improved production availability, and a reduction of 94.5 Million Metric Tons of CO2 per year.
There is another side, and there are strategies and tactics to the advantage of both the vendor and customer. Stay tuned for Part 2.
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