Launching a motor management program
Some people think that if they buy a "good" motor they will almost certainly have a reliable motor drive system. This is not necessarily the case. To help ensure that your "good" motor will reliably do the job it was meant to do — and achieve its life cycle goals — a comprehensive motor management program must be in effect.
Some people think that if they buy a “good” motor they will almost certainly have a reliable motor drive system. This is not necessarily the case. To help ensure that your “good” motor will reliably do the job it was meant to do — and achieve its life cycle goals — a comprehensive motor management program must be in effect.
Boeing’s motor management program was created by a group of engineers and condition-based maintenance professionals from facilities and equipment services, known internally as the equipment reliability improvement team. ERIT works with reliability issues of motors, driven equipment, lubrication, vibration, motor current analysis and thermography.
The team performed a detailed assessment of motor reliability requirements and used them as guidelines for managing motors in Boeing’s plants. This article is a summary of ERIT’s findings. There are no new discoveries, no proprietary processes — only a collection of best practices used in industry today.
Boeing’s motor management program applies to NEMA frame motors 1 hp and above and includes the following (Fig. 1):
New motor specification
Life cycle costs
Inventory and motor tagging
Modifications, moves, and rebuilds
Spares and motor storage
Proper application and failure analysis
New motor specification
You should be able to trace back each motor that comes into your plant to a motor specification that was tailored for your plant applications, environment, and operating conditions. The choice of which motor to buy should not be left up to equipment suppliers, consultants, or contractors; but should follow a carefully thought out plant-wide scheme for motor specification and procurement (see “Motor selection choices”).
The specification should be a plant standard that has evolved through a detailed, life cycle cost (LCC) analysis that supports your plant’s business plan. The motors should satisfy your plant maintenance program requirements, including lubrication, vibration, motor current analysis, etc.
Motor construction materials affecting cost and performance that enter into your LCC analysis should be addressed in the specification. It is not unusual for the initial cost of a motor to be less than 5% of its total life cycle electrical cost. Considering run time, efficiency, reliability expectations, life expectancy, and service environment, you may be able to make a good life cycle cost business case for purchasing higher quality motors (see “Life cycle cost worksheet”).
If the people authorized to order or supply motors for the equipment in your plant do not adhere to your motor specifications, you won’t know what kind of motor you will get. You may end up with a low bid, low quality motor that costs much more in its life cycle than a better quality motor that is more efficient and requires less maintenance.
There are several ways to obtain the features you want in a motor. One way is to write a lengthy specification and address each requirement, then find a supplier for your specified motor at a competitive cost. Another is to use an existing industry standard. For example, the American Petroleum Institute created a high-end motor specification suited to its industry titled the IEEE 841 motor standard. This specification goes beyond many of the ANSI MG1 basic motor requirements. For Boeing’s critical reliability needs, several tighter electrical and vibration requirements were added to those in IEEE 841 . Another approach is to standardize on a manufacturer’s model that meets your motor needs.
Life cycle costs
The objective of an LCC analysis is to choose the most cost effective course from a list of choices to achieve the lowest long-term cost of ownership. The LCC of a motor means exactly what the words imply — the sum total of all costs related to engineering, purchasing, shipping, installation, electrical, condition monitoring, maintenance, removal, disposal, and salvage for the life of the motor. If the motor is rebuilt and remains in service, the LCC would also include removing the motor from service, shipping it to the rebuild shop, the cost of the rebuild, return shipping, installation and eventual removal and disposal.
The LCC of motors in your plant should determine the quality of motor you choose as your standard. There is a great difference in quality required between a higher cost motor that you intend to have run for 20 years and a motor that only has to last a few months on a manufacturing research and development project or on a piece of tooling that will be obsolete and replaced after several years (see “Motor cost vs. long-term electrical costs”).
Motor inventory and tagging
It is important to have an accurate inventory of all the motors you have on site. You can build a history of individual motor failures and rebuilds if you have an accurate accounting of each individual motor. You can also make a better determination of the type and number of spare motors to keep on hand for quick replacement.
It may not be feasible to keep track of certain classes of motors for various reasons. For example, cabinet cooling fan motors may not be worth the effort to track individually. Determine which motors should be individually tracked (both in service and spare motors in storage) with a unique, easily identifiable tracking number. Choose a database system for tracking the motors. Preferably, use the plant-wide maintenance database, if available. Enter the motor nameplate data, the equipment the motor is driving, and the location of the motor.
Various reports can be generated with the particular motor data that is of interest at any given time. Boeing bonds a label onto the motor with both a readable number and a bar code. Using barcodes enables the use of handheld field device to scan the bar code label when work is performed on the motor, and then later download the information to the maintenance database computer system.
When installing new motors and rotating equipment, you should incorporate reliability requirements — from the initial project inception, through bid specification, design, fabrication, factory acceptance, field installation, commissioning, and final acceptance. The goal is to obtain and install motors and the equipment they drive with the highest reliability in the most cost effective manner, using LCC at junctures where decisions among alternative choices are to be made.
Motor reliability issues that you should consider throughout the aforementioned project phases include:
Understanding application and user reliability requirements
Supplying motor specification
Obtaining all relevant motor and driven equipment information needed for analytical instrument analysis
Meeting maintenance requirements, which include balancing, alignment, lubrication, thermographic, motor current analysis, and power quality.
New equipment placed into service in your plant should be tolerant of the quality of incoming electrical power. Equipment should not introduce power quality problems into the plant electrical power distribution system. New equipment specifications should address these power quality requirements. The equipment manufacturer or supplier should guarantee that the equipment complies with the power quality portion of the specification. The installer must meet the alignment, balancing, thermographic, and motor current analysis requirements of the purchase specifications as part of the commissioning and acceptance process.
Motor-driven equipment that is modified, moved, or rebuilt should meet all of the stringent requirements that new motor installations must meet in order to insure proper and reliable operation. They should be managed according to the same criteria as a new installation.
After a proper installation, it is usually the job of the maintenance or facilities department to keep the motor driven equipment running reliably for the life of the asset. LCC will drive the most cost-effective level of maintenance to be performed on the motor-driven system. The level of maintenance can range from run-to-failure, requiring no preventive or condition monitoring maintenance on noncritical equipment such as bathroom exhaust fans, to regular proactive monitoring of the motor system with vibration analysis, current analysis, tribology, and thermographic instruments on critical equipment. Boeing’s lubrication program requires monitoring the quality of its incoming lubricants, dispensing of oils and greases, and periodic sampling of oils from its critical equipment for oil analysis and occasional ferrography.
Boeing’s maintenance program continues to keep the equipment balanced and aligned to the same standards it requires of new installations. Key balancing and alignment requirements include balancing couplings and sheaves, performing balancing with proper key lengths, the effect of motor soft foot , cold vs. hot alignment considerations, and proper use of shimming materials.
Soft foot is a condition in which at least one foot of a motor or rotating machinery is not in the same plane created by the other feet. Tightening the mounting bolts causes the motor frame to twist, which affects shaft/coupling alignment, increases vibration, and causes premature bearing wear and/or failure. Soft foot can occur because of motor manufacturing defects, foundation and/or machine construction problems, or improper shimming during installation or maintenance.
Periodically, power quality should be checked on critical equipment with portable power analyzers and scopes. Power quality parameters that Boeing monitors include overvoltage, undervoltage, voltage transients, voltage unbalance, DC offset, and harmonics.
Boeing has used the following power quality values as a threshold during periodic checks in the plant:
Overvoltage and undervoltage — 10%
Voltage Transients — 50% of peak voltage
Voltage unbalance — 1%
Harmonics — voltage total harmonic distortion
(THD) — 5%
Spares and motor storage
It is important to develop and implement a comprehensive motor storage plan. Plant motor inventory analysis helps you determine the proper sizes and quantities of motors to keep on hand as spares. Spare motors must be properly stored and maintained so that they function properly when put into operation (see “Tips for proper motor storage and maintenance”). An improperly stored motor may fail shortly after being put into operation, causing disruption to operations and an increase in operating costs.
If your plant is located near a major city, it may be possible to have your motor supplier stock your most common motors for you. This allows you to stock fewer spare motors — potentially freeing your company’s capital that would otherwise be tied up in motor inventory. Also, whenever possible, work toward plant commonality to further reduce your motor inventory.
Proper motor application and failure analysis
Prior to purchasing a new motor, its application should be verified. Whenever a motor failure occurs, a root cause failure analysis should be performed before a replacement or repaired motor is put into service. It is important to determine why the original motor failed. Failure analysis enables you to take effective corrective action to prevent future failures.
When assessing whether a motor is appropriate for a particular application, consider how the motor’s design parameters will affect the motor while it is in service. For example, the most efficient operating point for many 10 hp motors is around 70% motor loading. In some instances, motors should be sized to operate in that load range (Fig. 2).
Motor run time and motor efficiency values can affect long term LCC. Therefore, you should always validate your decisions by running the numbers. Parameters to consider include:
Maintenance history of similar motor applications: previous failures, preventive, predictive, or run-to-failure maintenance
Operational requirements: min/max speeds, thrust, torque, bumping, plugging, and number of starts per hour
Environment: temperature, vibration, and chemical exposure.
Failure analysis of a motor-driven system should be done immediately after the failure occurs, whenever possible. Find out what caused the failure before relevant information is lost and before the system is repaired and put back into service. Recommendations can then be made and implemented to prevent the failure from recurring.
Root cause failure analysis should also be carried out. Although the majority of the direct causes of unreliable system performance are equipment failures or human errors, the process of equipment management is typically the underlying root cause. The equipment management system weaknesses let the organization or department get to the point of allowing opportunities for unreliable equipment performance or human error to creep into the process at any of the various stages of equipment management — from specification and procurement through installation, operation and maintenance.
Plants use quality control to ensure that processes or products conform to the specifications established for them. The elements described in this article — a good motor specification, proper installation, proper maintenance, proper storage of spare motors, etc. — should be included in a successful motor management program. If any of these elements are not properly administered, higher costs to your maintenance department and more downtime will result in higher costs to your customers.
The department responsible for acquiring, installing, and maintaining motor-driven systems must devise a quality control plan for successfully implementing motor management. You should ensure that each step of the motor management program is executed properly to minimize LCC.
Every situation is different. It’s up to you to craft your motor management program to fit your needs. Launching a successful motor management program requires a conscious, deliberate effort. Otherwise, the result will be a continued mix of motor reliability problems and the inherent higher costs associated with them — many of them hidden.
The authors are Equipment Reliability Engineers in The Boeing Company’s Commercial Airplane Div., Seattle, WA. Mike Kozak is a professional electrical engineer; Bill Shinpaugh is a professional mechanical engineer. Together, they have more than 50 years of industrial experience. They are available to answer questions about this article, and can be reached at firstname.lastname@example.org and email@example.com . Article edited by Jack Smith, Senior Editor, 630-288-8783, firstname.lastname@example.org .For further information about motor management, visit the following web sites:
National Electrical Manufacturers Association (NEMA)
Refer to Standard MG-1
MotorMaster+4.0 is a software program that analyzes motor and motor system efficiency. Designed for utility auditors, industrial plant energy coordinators, and consulting engineers, MotorMaster+4.0 is used to identify inefficient or oversized facility motors and compute the energy and demand savings associated with selection of a replacement energy-efficient model.
A joint effort by the U.S. Department of Energy (DOE), industry, motor/drive manufacturers and distributors, and other key participants. The goal is to put information about energy-efficient electric motor system technology into the hands of people who can use it.
Motor Decisions Matter (MDM)
Department of Energy (DOE)
Electrical Apparatus Service Association (EASA)
PLANT ENGINEERING magazine
Life Cycle Cost Worksheet
Manufacturer Description New motor purchase Brand X High efficiency Brand Y IEEE 841 * Sometimes it is necessary to disassemble a motor to make it meet specifications before installation.
** If the life of the motor you select is less than the project life, you must purchase and install additional motors.
HP 10 10 RPM 1800 1800 kW/hp 0.746 0.746 kW 7.46 7.46 Frame 215T 215T Nameplate efficiency @100% 85.5% 91.0% Initial cost $400 $623 Run time (hours/wk) 80 80 Run time (hour/year) 4160 4160 Current cost/kWh 0.06 0.06 Annual electrical cost $2,177.80 $2,046.17 Anticipated motor life (years) 12 20 Installation hours (maintenance) 2 2 Installation cost (maintenance) $84.00 $84.00 Preinstallation rebuild/balance-CBM* 2.5 0 Annual maintenance lube hours 0.1 0.1 Annual CBM hours (vibration testing) 0.25 0.25 Maintenance/CBM cost/hour $42.00 $42.00 Project life (years) 20 20 Estimated motors needed for life of project ** 1.7 1.0 Actual motors needed 2.0 1.0 Life Cycle Costs Maintenance-lube $84.00 84.00 Maintenance-installation $168.00 84.00 CBM-vibration $210.00 210.00 CBM rework $210.00 0.00 Electrical cost $43,555.93 40,923.43 Motor cost $800.00 623.00 Project life cycle cost $45,027.93 41,924.43 Life cycle cost difference 3,103.50
Motor selection choices
Examples of choices that must be made when selecting a motor include:
Frame bases — bolted base, rigid-removable base, rolled steel rigid welded mounting, cast iron feet, etc.
Frame material — rolled steel, aluminum, die-cast aluminum, cast iron, cast iron end shields, etc.
Frame type — ODP, TEFC, TENV, etc.
Mounting — horizontal, vertical, both
Bearings — ball vs. roller, sealed, shielded, regreaseable style or not, labyrinth seals, etc.
Insulation — B, F, inverter duty, etc.
Balancing requirements — precision balanced, special balanced, to G1 standards, API standards, etc.
Warranty — 2 year, 3 year, 5 year, etc.
Motor cost vs. long-term electrical costs
This table illustrates how the motor cost, electrical cost/year and long-term electrical cost relate to each other over the assumed life of the motor. The original cost of the motor becomes less significant as the motor size, length of service, run time, and electrical costs increase. Conversely, these same factors may provide a different financial picture if electricity is cheap and run time is low. This is why you must examine the LCC of each project. Each element has a contribution, and the best way to get the whole picture is to do the math.
The electrical costs in this table have not been adjusted for inflation over 20 years. You also won’t be using a motor with 100% efficiency. You should create a similar table using your own local numbers to validate and apply this concept.
Electrical energy cost = $0.06/kWh (based on Boeing’s cost; your cost may differ)
Run time = 80 hours/week
Efficiency = 100%
Motor hp Motor cost Annual electricity cost Electricity cost Motor cost as a percentage of total electrical cost over 20 years 1 $221 $186 $3,724 5.9% 5 $302 $931 $18,620 1.6% 10 $494 $1,862 $37,240 1.3% 25 $965 $4,655 $93,101 1.0% 50 $1,865 $9,310 $186,202 1.0% 100 $4,185 $18,620 $372,403 1.1% 200 $7,800 $37,240 $744,806 1.0% 300 $10,600 $55,860 $1,117,210 0.9%
Tips for proper motor storage and maintenance
Recommended motor storage requirements should include the following:
Motor current analysis and resistance readings should be taken when a motor is put into and taken out of storage
External parts should be coated with a rust inhibitor
Motors should be covered
Ventilation openings should be protected from rodent entry
Storage area should be free from shock or vibration
Temperature and humidity should not be extreme
Ball and roller bearings should be greased and purged annually
Sleeve bearing reservoirs should be filled with oil to the proper level
Motor shafts should be hand rotated 10 to 15 turns every month or two