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Many are aware of the use of motor circuit analysis and infrared imaging in a predictive maintenance (PdM) program for motors. It is a program that, when performed properly, increases uptime, reliability and productivity, ultimately impacting the thing most managers want to see: lowered or stabilized maintenance costs. However, there may not be an understanding or awareness of the benefits and impact that an effective motor management system can have on that cost.
This article will show basic key elements for a motor management system and provide an understanding of why a motor management system is much more than just a reliability and testing program. In fact, motor reliability and testing are two key components that make a significant contribution to a motor management system.
Infrared thermography is just one part of an effective motor management system.SHORT STORY
In the meantime, this newly promoted supervisor was given approximately nine hats to wear. One of them was to oversee the Motor Shop. So, where else could he start? With a bit of authority that accompanied the promotion, he created a team. A few questions got answered, a few things changed. Before anyone knew it, a motor management system began to take shape.
The first six months were very difficult indeed, and another 12 rough months would pass. After 18 months, a faint glimmer of light could be seen at the end of the tunnel. Though people had fought tooth and nail against it, a few eyes began to flutter and some popped open when it was revealed that repair, inventory and purchase costs had been reduced nearly $1 million. Suddenly, the questions, ideas and actions no longer seemed so trivial.
Looking back, it was easy to see the well-traveled road littered with the debris of good intentions, false assumptions, erroneous information, etc. All this and more created a climate where bad decisions were made and money wasted.
As an example, the first practice stopped in those first 18 months was repairing motors for $900 that only cost $200 when new. This was just the tip of the iceberg. Energy-consumption issues were later added to the equation, as well as other reliability principles and testing.WHAT IS IT?
A motor manager: someone who is in charge and accountable
Storage: outdoors is not acceptable
A preferred, accountable repair facility
Repair specifications for the repair facility to use
A cost-saving contract for purchasing new motors from a primary vendor
Reliability testing: off-line, on-line, infrared and even vibration
Acceptance testing of repaired motors and new motors, if possible
Tracking motors from purchase through scrap and the history in between
A decision tree for determining repair vs. replacement
A system to address energy consumption and efficiency
Once an effective motor management system has been in operation for a time, and employees and other managers become educated as to how it works, it should become easier to manage.STORAGE
Warehouse personnel are normally tasked with the day-to-day activities of normal motor storage - from receiving, issuing to and shipping to the repair shop. Personnel should be familiar with how to handle and store motors to avoid incidental damage during the storage process.
Large AC motors (high voltage) sometimes need special handling and storage areas. Connect motors with internal heaters to a voltage source while in storage to keep the windings dry.REPAIRS
A contract with a preferred repair facility can be negotiated to reduce repair cost over what it may have been. An ideal situation would be that the repair facility is also a dealer for the preferred new motor vendor.
Then there are the special, one-of-a-kind and non-standard motors that have to be addressed. Have you seen the suffix TY, TCY, TZ or TCZ (for instance, 286TCZ)? If so, they are the "non-standard" variety and might only be acquired from an original equipment manufacturer (OEM), not the motor manufacturer.
If the OEM is totally out of business (not acquired by another company), a replacement motor may not be available. Having the right repair facility can come in handy with these motors. Also, by having an understanding of what alternatives are available and the knowledge of what to use as a substitute, the plant can stay running.NEW MOTORS
Engineering: Is the motor designed and/or repaired to perform the task it is asked to do?
Testing: motors and their circuits.
Infrared: It is very important to have baseline images and stated "normal" temperatures.
Vibration: baseline data.
When testing or inspecting a motor, it is important to ask, "Is this the motor I think it is?" or "Was this the same one that was there the last time?"
A motor reliability and testing technician shouldn't be considered the motor manager. However, the tech is a key partner in the management of motor assets, along with maintenance managers, mechanics, warehouse people, purchasing people, etc.
The reliability and testing technician also should have a working relationship with the preferred repair vendor in order to assist in problem resolutions.DECISION TREE
Most decision trees lack one important item. This is a branch or section to help determine whether a motor should be equipped with a roller bearing on the shaft end. This is a critical decision for motors driving equipment through belts. Don't construe this to mean that all motors driving belts should have a roller bearing on the shaft end. Each case should be considered separately as to whether a roller bearing would be applicable. This issue is also very important when making a purchase decision for a new motor.TRACKING
The area where the J-box is mounted normally provides a large enough surface area, as do other areas on the motor. Don't engrave end bells with the identifier in the event an end bell is replaced. The engraving should be as deep as possible and legible. Stamping is not recommended because there is a risk of cracking the casting.
Relying on the nameplate for identification can be frustrating, especially if the nameplate is removed or becomes unreadable because of corrosion, etc. Motor shops often install a replacement nameplate, but only the basic information is usually put on it and other important information may be lost if not recorded elsewhere.
There are a number of ways to set up an identifier, but it should be uniform and not change from year to year. For example, a numeral system based on the year and the sequence the motor arrived can be assigned along with a letter designation for the name of the site - for instance, 99-035V. The 99 means it was 1999. The 035 means it was the 35th motor identified in 1999. The V stands for the name of the plant site. If it was an older motor that had not yet been identified, it would be assigned the next sequential number.HISTORY
History can be kept in many forms (a sample is shown below) and is normally tailored to a particular site or company. Whatever form it takes, it has to be easily used and not fragmented in different places to get a complete picture.
A number of motor testing systems allow for history entry and retention. However, they present some limitations in regard to documenting a complete birth-to-death history, especially if there is no formal motor management system in place. History then becomes fragmented and sometimes of little use unless diligently administered. History is the lifeblood of any motor management system.
ID: 99-035V Shop #172986 50-1780-326TPH S/N: none
US Electric 460v 65 FLA 90-eff 82-pf 56 Bars 48 Slots
Note: Open style, vertical mount, shaft down, oil bath top bearing
02/15/1999 - New motor: PO 14598V: Acceptance ck good: Test Run OK
02/20/1999 - Installed: 40628971P: #1 River water pump: w/o V179263
10/31/2003 - Removed: 40628971P: Grinding noise: No oil: w/o V613578
11/15/2003 - From Repair: Acceptance ck good: Reconditioned
05/16/2004 - Installed: 40628972P: #2 River water pump: w/o V798642
Note that ...
Reconditioned = Bearings, machining, cleaning, painting, etc.
Overhauled = Rewound along with reconditioned items.
According to the U.S. Department of Energy, electric motors consume a large percentage of electricity used in American industry. On average, approximately 63 percent of industrial electricity is consumed by electric motors. This percentage can reach 75 percent or more in certain industries. Also, motors can consume five to 12 times their initial purchase cost in energy per year. If you consider that a 25-horsepower motor, running 24/7, can consume up to $15,000 in energy per year and a 100-horsepower motor can consume up to $56,000 in energy per year, even small reductions in energy consumption per motor could result in substantial savings. Additionally, in the case of motors up to approximately 50 horsepower, the savings difference between using a standard-efficient vs. a premium-efficient motor could pay for the premium motor in one year. Every year after that would be money in the pocket.
Repair practices and quality can significantly influence energy consumption over original design. A rewound motor, especially if it was poorly done, can significantly increase energy consumption compared to the original "as built" specifications. That's a very important item to consider when making repair and replace decisions.CONCLUSION
A motor management system, functioning at all levels, makes life easier, reduces cost, reduces inventory and reduces energy usage. This keeps everyone happy, including the reliability and testing technician.
Elmer DeForest, CMRP, is a field technician and technology leader for Snell Inspections. This paper was originally presented at Snell’s 2007 Thermal Solutions Conference. To learn more about infrared applications or the conference, call 800-636-9820 or visit www.snellinfrared.com.