Electric Motor Repair vs Replacement – How to Choose?
May 2, 2016
What’s up with motors?
Motors are reliable as can be when managed and maintained properly. To a point. Then they still fail. It’s up to you to then make decisions quickly and get production running again
Here’s the rub. You need to realize that the decisions made during these times can significantly impact future reliability and efficiency of equipment. So maybe a deep breath is in order.
From my experience, I see way too often when a quick decision is not the right decision. Here’s an example: A major steel company had a hydrogen annealing fan application. They were spending an average of $3,000 to repair a small fan motor on emergency (5HP, 1800RPM, 184TZ, 460V, TEAO).
Ready for this?
They were averaging 54 repairs per year. At $3,000 per repair. That adds up to $162,000 annually. And yes, that’s a lot. Especially when you consider the average life span was 6 months.
Everything was an emergency and they never had time to do the repair properly. Their supplier was just repairing them and not giving them any solution to keep them from failing again. And the cash rolled in.
We see this a lot when a customer is under the gun to get the motor back as soon as possible, and doesn’t allow enough time to do the right thing. And we totally understand why you are getting pressure.
The purpose of this blog is to explain a systems approach in helping to solve this situation and others like this
It starts with creating a best practices Repair/Replacement Plan
Creating a Best Practices Repair/Replacement Plan on the front-side, before a failure occurs, will allow you to be prepared for a failure. You will know — not have to guess — what to do. And you won’t jeopardize long-term reliability because of a short-term focus.
Having the right plan will allow the you to:
- Maximize plant availability
- Minimize in-service equipment failures
- Reduce the time it takes to get equipment operating again at best practice
- Provide a systematic approach to improving the efficiency and reliability of your motors inventory over time
- Enable you to predict outcomes when dealing with in-service equipment failure
- Result in the lowest overall cost to your business.
For the plan to work best, it should complement existing maintenance practices and should cover:
- Establishing a motor and plant inventory
- Setting a repair/replace breakpoint
- Partnering with the right supplier
- Establishing repair pricing
- Negotiating contractual replacement pricing
- Repair v/s Replacement comparison
- Managing repair vendors:
- Assessing the capability of repair vendors
- Developing technical specifications to mandate the quality of the repair/replacement
- Developing a document management process and preventative action plan
- Removal and Installation checklist
- Evaluating results
- Developing a standard decision making process for dealing with failures
Repair/ Replacement Plan
With a good Repair/Replacement plan on hand, you’ll have the information you need when a failure occurs, and you’ll be able to manage and minimize in-service equipment failure.
If set up correctly, your motor and plant inventory will serve as a centralized source of all the information you need to quickly make informed decisions. The inventory creates guideline statements on the best replacement option or repair specification, which will help guide you in the right direction when failure occurs.
Way too often we get a call for a motor and are given limited data. Precious time is then wasted waiting to be provided more, and accurate, information. Getting the right information on the front side will speed up the process and assure that the right motor is found.
That is particularly important if you don’t have a replacement in stock. Then providing the right information to the electric motor repair shop or new motor supplier will assure that you get the right motor.
Be sure you can provide this info:
Complete nameplate information (Picture of nameplate)
Description of Driven Application
Larger motors will require additional information like:
Speed v/s Torque curves
Load Inertia (wk2)
Do you have a repair/replacement breakpoint?
It is important that you establish a repair/replace breakpoint — a motor size below which you should automatically replace a motor. This breakpoint should be clearly available to decision makers utilizing software such as HECO’s TracRat™.
The decision to repair or replace should predominantly be a financial one. While repairing the motor may require fewer initial costs than purchasing a new motor, the total operating costs of the repaired motor may be significantly higher depending on the:
- Cause of failure
- Age of your motor
- Ability of your repair shop
- Annual operating hours of the motor
- Overall efficiency of the motor after repair
Once a motor falls below a certain size, it is not economical to repair. For standard, AC Induction, “T-Frame” motors that size will typically be around 50 to 75 HP, or the motor size at which a repair is worth more than 60 to 70 percent of the replacement cost for a higher efficiency motor.
By starting your repair/replacement analysis with larger motors and working down to smaller motors, you will be able to establish a point at which it becomes obvious that replacement is the best option for your organization.
Establish replacement pricing with your repair partner.
Since the decision to repair/replace is primarily a financial decision, it is important to discuss and establish repair pricing.
Generally, it is recommended to do a matrix type format that is based on your motor and plant inventory. However, sometimes a simple PO history on motors can give you average prices on repairs. It’s a basic, yet gives you a tool to make a decision.
Whatever process you use, you must have something to compare your repair pricing to in order to make a determination. That is where having established, contractual, replacement pricing will allow you to know the cost of a replacement. If you don’t have that now, well, better late than never. Find a repair supplier you trust and start building a foundation.
One key factor that is often overlooked is that the new motor could have a substantially higher efficiency rating. This should be factored in your decision making process since only 5% of the total cost of ownership for a motor is in the purchase price and maintenance costs – the remaining 95% of the TCO is energy costs.
Purchase price vs energy costs
Here is a breakdown of how much one 200 hp, 1,800 rpm and 460 V TEFC motor costs in power in a calendar year (7,200 hours of operation):
- Average cost of power in the United States: $.068/kWh
- Annual power cost: $70,669
- Initial purchase price: Slightly more than $10,000
Considering those factors, one 200 hp pump motor running 6 days a week for 50 weeks a year will cost more than $70,000 dollars at the end of one year. Interestingly enough, most end-users spend more time negotiating the initial purchase price of a motor than understanding the true cost for operating that motor.
Repairing v/s Replacing? How do you decide?
Here are some things to consider when making the decision:
- In some cases, repair is best based on the application and design of motor. New designs may be more efficient, but the original motor is better suited than the current replacement.
- In the past, motors were built to last 25 to 35 years, but most were over engineered
- Today motors are designed to last 15-20 years, but are engineered with little to no leeway
- Current replacement motors are generally smaller, making it sometimes harder to install in the original application’s location.
- Is the new motor able to be rebuilt by a repair shop, or does it have to go back to the OEM?
- Is the lead time for a new replacement too long for your current needs and repair is the only feasible option?
Managing repair suppliers
Develop a strategy for managing repair vendors to cover cases when replacement is not the best option. This will help ensure that your motor is returned to service in line with appropriate standards, in reliable condition and is able to operate efficiently. Your strategy should cover:
- Assess the capability of repair vendors
- Develop technical specs to mandate the quality of the repair
- Develop a document management process and a preventative action plan
One more important point, all repair shops weren’t created equal. Without proper repair methods, motor rewinding could reduce motor efficiency by as much as five percent. It can also reduce reliability, leading to a significant increase in energy costs and the risk of further equipment failure.
Assess the capability of your vendors
You should carefully assess the capability of repair vendors and, once you select the correct one, establish a partnering relationship to ensure your motors are repaired to an optimum level of reliability and efficiency.
There are many ways to assess the capability of a repair vendor (repairer):
- Check whether the repairer is an EASA member and follows EASA motor repair standards.
- What other standards do they follow? (Vibration, IEEE, etc.)
- Ask the repairer to describe how they meet various standards covering; for example, the overhaul and repair of electric motors.
- Ask your repairer if they have a Quality Manual outlining their capabilities to undertake the work. The repairer should be able to demonstrate that they have the right equipment and processes to handle, repair and test your motors.
- Visit the repairer to inspect their premises.
- Meet face-to-face to review your specifications with the repairer, and ensure you both have a common understanding of what is expected.
- Ask your repairer to outline their continuous improvement and training programs. Ask for details on the skill levels of the technicians who will be working on the repair. Ask if the repairer has an in-house training program that focuses on all aspects of repairing motors, but especially on preserving design and efficiency characteristics of motors.
- Discuss how you can work together to continually audit/measure the performance and quality of the work, to ensure your organization benefits from continuous improvement.
Develop technical specifications
Develop detailed specifications for your repairer, clearly stating both exception and rejection criteria. They need to fully understand your organizations’ requirements for energy efficiency and reliability. Sharing detailed information is what governs the ultimate outcome of the repair.
Your specifications should be prescriptive and aimed at ensuring that the repaired motor matches the ‘as designed’ motor in every respect. Clearly articulated specifications will eliminate corner-cutting and mistakes that can lead to motors running inefficiently and unreliably.
Your specifications should include:
- A statement on the intent and scope of the repair
- A schedule of relevant standards
- Requirements for condition reporting
- Requirements for the repair and overhaul of windings
- Requirements for the repair and overhaul of the rotor
- Requirements for mechanical overhaul
- Requirements for verification testing.
Like the repair specification, developing a New Motor specification that clearly defines the construction, design, efficiency, and approved brands will help to insure reliability and consistency.
Develop a document management process
Develop a document management process and preventative action plan and use it to compile and maintain accurate reporting on your repairs. Regularly review your repair reports to identify areas for improvement relating to in-service testing and operation of your motors. Incorporate opportunities for improvement into your preventative action plan (which should be part of your maintenance schedule).
Your document management process should cover:
- Initial details on the condition of your motor when it is received by the repairer
- A ‘condition report’ providing an assessment of the condition of the motor after it is disassembled and initially tested
- A ‘failure report’ detailing findings on motors that have failed in-service
- Full details of the repair
- Results of all tests (mechanical and electrical) carried out during repair
- A statement of how the repair meets your specifications and conforms to best practice.
Quality documentation processes
At HECO, we’ve created a Quality and Documentation Process that includes:
Exception Report created for your requirements:
- 20 different paperwork packets designed for different types of electric motors, including:
- AC Sleeve Bearing Motors
- AC Vertical Motors
- AC Ball Bearing Motors
- DC Motors
- DC Sleeve Bearing Motors
- Eddy Current Clutches
- Detailed failure assessment
Clearly defined initial expectations can provide the basis for regularly scheduled meetings with selected vendors. You should expect the vendor(s) to bring to their “evaluation meetings” all relevant reports that demonstrate compliance with the best practice Repair/Replacement plan.
What goes around comes around
Remember the example I started this blog with? The major steel company that had a hydrogen annealing fan application that they were spending $3,000 average to repair a small fan motor on emergency (5HP, 1800RPM, 184TZ, 460V, TEAO)?
- They were averaging 54 repairs per year at $3,000/repair, spending $162,000 annually
- Average life span of 6 months
- Everything was an emergency
- There current supplier was just repairing them and not giving them any other solution
- Customer asked us to get involved and to look at the root cause
- The first few motors we received had been patched together.
What we found:
- We found that the bearing size was not big enough to handle the load
- The motors were not sealed properly for the application
- Fans had not been balanced
- Fan housing assembly that was flexing
The customer wanted us to improve the life of the motor. The first few motors we repaired, we replaced bearing housings with new, sealed the motors, VPIed the windings, and balanced the fans.
This increased the life to more than double.
We felt this was not good enough so we looked at the whole application
- We found that the fan housing was flimsy causing additional vibration problems
- Bearings were undersize for the fan weight
- Motor had to be sealed better
So we redesigned the whole application
- We took a standard severe duty motor and increased the bearing size
- We manufactured a new reinforced fan housing with new fan
- Cost to manufacture a new complete fan assembly $7,523 per unit
- The life span increased so far over 15 months without a failure
In just this one application the pay back was less than one year (This didn’t include downtime loses or cost to remove and install). By taking a more systematic approach and breaking it into a Best Practice Repair/ Replacement plan you will find it a lot easier to make decisions when a failure happens.
Need help making the decision?
HECO can help you with any questions you may have choosing between repairing and replacing electric motors. We’ll begin by asking “Why?” Why did your current motor fail? What can be done to keep it from failing again? Exactly why would a repair or a replacement be best for your particular application?
Then we’ll use our problem solving and engineering expertise to provide a systems-oriented tailored to your specific needs.