Energy efficiency

Reference manual

  1. Introduction: setting the scene 
  2. Selecting the best motor and equipment 
  3. Commissioning 
  4. Motor and system maintenance and operation 
  5. Motor repair and replacement 
  6. Utility management 
  7. Maintenance management systems: plant inventory and records 

Motor repair and replacement

Motors are inherently reliable but over time they do need to be repaired or replaced. When motors fail, organisations must act quickly to get them running again. The decisions you make when a motor fails can significantly impact on the future reliability and efficiency of your equipment.

This section outlines a best practice approach for dealing with repair and replacement decisions. This approach will enable you to act decisively when a failure occurs, with the confidence that your decisions will improve the performance of your motor inventory and provide maximum return for your organisation.

This section explains the importance of developing a motor failure management plan, including establishing a motor and plant inventory, setting a repair/replace breakpoint, undertaking a pre-failure analysis, developing a decision making process, and managing repair vendors.

Developing a best practice motor failure management plan

A best practice motor failure management plan aims to:

You can develop such a plan for any population of operating motors. It should complement existing maintenance packages and management practices and cover:

  1. establishing a motor and plan inventory
  2. setting a repair/replace breakpoint
  3. undertaking a pre-failure analysis
  4. developing a standard decision making process for dealing with failures
  5. managing repair vendors:
    • assessing the capability of repair vendors
    • developing technical specifications to mandate the quality of the repair
    • developing a document management process and preventative action regime.

Establishing a motor and plant inventory

Regardless of whether you have one or hundreds of electric motors operating in your business, you should establish a motor inventory. Having the right information on hand when a failure occurs will enable you to manage and minimise in service equipment failure and reduce downtime and operating costs - all in the best interests of your organisation.

If set up correctly, your motor and plant inventory will serve as a centralised source of all the information you need to quickly make informed decisions. It should contain a statement on the best replacement option or repair specification, which will help guide you in the right direction when failure occurs.

The key elements you need to incorporate into your motor and plant inventory are described in Maintenance management systems: plant inventory and records.

It is important that you establish a repair/replace breakpoint - a motor size below which you should automatically replace a motor.

The decision to repair or replace should be predominantly 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:

A new motor is likely to last longer and have a longer warranty.

Once motors fall below a certain size, they are not economical to repair. That size will typically be around 15 kW, or the motor size at which a repair is worth more than 60 per cent of the replacement cost for a higher efficiency motor. By starting your pre-failure analysis with larger motors and working down to smaller motors (see below), you will be able to establish a point at which it becomes obvious that replacement is the best option for your organisation.

Undertaking a pre-failure analysis

You must establish the best replacement option for motors sized above the repair/replace breakpoint before they fail. You can use the Motor Selector software to help you to calculate the life cycle cost of each option, and take into account any reductions in motor efficiency caused by the repair process. You can save the Motor Selector analysis and log the file details into your plant inventory. When a failure occurs, you can quickly review this analysis, update it with the latest price information and use it to quickly determine the best replacement option.

Developing a standard decision making process for dealing with failures

Use the decision making flow chart below as a basic decision tool that you can adapt for your organisation's particular needs. It will ensure that you make the right decisions at the time of failure. All staff involved in motor repair will need to be aware of the flow chart and follow the process it outlines.

Decision making flow chart

Managing repair vendors

Without proper care, motor rewinding can reduce motor efficiency by as much as five per cent. It can also reduce reliability, leading to a significant increase in energy costs and the risk of further equipment failure.

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:

Assessing the capability of your repair vendors

You should carefully assess the capability of repair vendors and, once you select the best one, you need to establish a partnering relationship to ensure your motors are repaired to an optimum level of reliability and efficiency against Australian standards and codes of practice.

There are many ways to assess the capability of a repair vendor (repairer):

Developing technical specifications

Develop detailed, accurate and complete specifications for your repairer, clearly stating both exception and rejection criteria. They need to fully understand, for example, your organisations' requirements for energy efficiency and reliability. Sharing detailed information is what governs and controls 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. Well thought through and clearly articulated specifications will eliminate corner-cutting and mistakes that can lead to motors running inefficiently and unreliably.

Your specifications should include:

  1. a statement on the intent and scope of the repair
  2. a schedule of relevant standards
  3. requirements for condition reporting
  4. requirements for the repair and overhaul of windings
  5. requirements for the repair and overhaul of the rotor
  6. requirements for mechanical overhaul
  7. requirements for verification testing.

Developing a document management process and preventative action regime

Develop a document management process 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:

  1. initial details on the condition of your motor when it is received by the repairer
  2. a 'condition report' providing an assessment of the condition of the motor after it is disassembled and initially tested
  3. a 'failure report' detailing findings on motors that have failed in-service
  4. full details of the repair
  5. results of all tests (mechanical and electrical) carried out during repair
  6. a statement of how the repair meets your specifications and conforms to best practice.

Motor Solutions