Lean Maintenance & Reliability

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"Health of the machines decides the health of Organisation"

Maintenance & Reliability forms a part of multi-level and multi-tool approach Total Productive Maintenance.


Maintenance is primarily the act of keeping a property or equipment in good condition by making repairs in timely manner and up-keeping it in the best shape so as to extract the best quality, in time and in full from it.


Reliability, in maintenance management, encompasses everything that machinery interacts with – technology, culture, and design and maintenance strategy


What is Total Productive Maintenance – TPM?

TPM – Total Productive Maintenance is a pillar of Total Lean Management and a maintenance philosophy aimed at eliminating production losses due to equipment ill functioning. TPM is about keeping equipment in a position to produce at maximum capacity, the expected quality products, with no unscheduled stops. The JIPM (Japan Institute of Plant Maintenance) definition of TPM is
T = Total, Must involve all employees at all levels of the organisation
P = Productive, Effective utilization of all resources
M = Maintenance, Keeping the Man-Machine-Material system in optimum condition


Total productive maintenance has eight pillars that aims at proactively establishing reliability of machines. While focusing on equipment effectiveness, one point that has to be made here is that people are centre of this system and must be continually trained to identify and eliminate waste. It is a system that is based on a clear set of principles and structures and should not be interpreted to be a set of tools or techniques to be applied haphazardly in a view of creating a Lean Environment.

The 8 pillers of TPM

  1. Focused Improvement – provides a structured, team-based approach to drive elimination of specifically identified losses in any process Industry
  2. Autonomous Maintenance –follows a structured approach to increase the skill levels of personnel so that they can understand, manage and improve their equipment and processes
  3. Planned Maintenance – aims to achieve zero breakdowns with an approach to establish a management system that extends the equipment reliability at optimum cost
  4. Training and Education – aims at ensuring that staffs are trained in the skills identified as essential both for their personal development and for the successful deployment of TPM in line with the organization’s goals and objectives
  5. Early Management – aims to implement new products and processes with vertical ramp up and minimized development lead time. It is usually deployed after the first four pillars as it builds on the learning captured from other pillars
  6. Quality Maintenance – aims to assure zero defect conditions by understanding and controlling the process interactions between manpower, material, machines and methods that could enable defects to occur
  7. Office TPM – concentrates on all areas that provide administrative and support functions in the organisation to assist the optimization of manufacturing processes and that they are completed at optimal cost
  8. Safety, Health and Environment (SHE) – implements a methodology to drive towards the achievement of zero accidents. It is important to note that this is not just safety related but covers zero accidents, Zero overburden (physical and mental stress and strain on employees) and zero pollution



OEE (Overall Equipment Effectiveness) is a metric that identifies the percentage of planned production time that is truly productive. It was developed to support TPM initiatives by accurately tracking progress towards achieving “perfect production”.

  • An OEE score of 100% is perfect production
  • An OEE score of 85% is world class for discrete manufacturers
  • An OEE score of 60% is fairly typical for discrete manufacturers
  • An OEE score of 40% is not uncommon for manufacturers without TPM and/or lean programs

OEE measures six categories of equipment losses throughout its system.

  • Equipment failure
  • Set up and adjustment
  • Idling and minor stoppages
  • Reduced speed
  • Defects in the process
  • Reduced yield

How to measure OEE?

OEE = Availability × Performance × Quality

Availability factor: It is one of the basic criteria to measure OEE and machine utilization is the most important component of availability.

Performance factor: It is the record of output, which determines whether producing and delivering a product or service as per standards.

Quality factor: It shows the amount of parts/products produced that fully satisfies the pre-set and intended quality standards.


What are MTBF & MTTR?

MTBF (Mean Time Between Failures) & MTTR (Mean Time To Repair) are two metrics used for more than 6 decades now, as indicators of the availability of an equipment. These are considered as KPIs from production perspective in world’s best Lean practicing organizations. These metrics gives a brief idea of the overall uptime of your equipment – the productive time it contributed to overall performance.

What is MTBF?

MTBF (Mean Time Between Failures) – It is the average amount of operating time between consecutive breakdowns for an item of equipment (or plant).

MTBF = Operating Time / Number of Failure or Breakdown Events
  • Operating time is productive time plus production delays.
  • Number of failures or breakdown events is the number of failures on an item of equipment (or plant).

What is MTTR?

MTTR (Mean Time To Repair) – it is the average maintenance time required to keep an item of equipment (or plant) operational.

MTTR = Total Downtime / Number of Failures or Breakdown Events
  • Down time is the total time equipment (or plant) is down for maintenance work (preventive and corrective).
  • Number of failures or breakdown events is the number of failures on an item of equipment (or plant).

Uptime = MTBF / (MTBF + MTTR)

Importance of MTBF & MTTR

As reliable production processes are crucial in a Lean Manufacturing environment, MTBF and MTTR are vital metrics for all lean initiatives. The goal for Lean Improvement s with respect to these KPIs should be:

1. MTBF should increase with the improvements
  • This means the frequency of equipment breakdown gets lesser over the time
  • Can be achieved through timely maintenance by maintenance team and operators
2. MTTR should decrease with improvements
  • If and when a failure occurs, the equipment or facility gets back to good working condition quickly
  • Can be achieved through spares inventory planning and in depth training of maintenance procedure to operators and maintenance team


What is SMED?

SMED, abbreviation of Single Minute Exchange of Dies (also commonly referred as QCO – Quick Changeover), is a process of reducing changeover (setup) between exchange of setup of a product taken out of production and taking up new product for production.

How to perform SMED?

The key to success is to move as many setup tasks from internal setup to external setup, then reduce the time needed to complete the internal tasks.

  • Internal setup – can only be performed when the machine is down
  • External setup – can be performed when the machine is running

Conceptual stages of SMED:

  1. Separating internal and external setup
  2. Converting internal to external setup
  3. Streamlining all aspects of the setup operation


The customer won’t pay for something that you haven’t produced. So anytime that is consumed as downtime is a waste, MUDA of waiting to be precise, since the new product is waiting for the machinery to be set-up for it. This downtime is not something that is not foreseen. Instead it is something that is always planned. Hence the time consumed during this changeover shall always be restricted to the minimum value as much as possible.


A successful SMED program will have the following benefits:
  • Lower manufacturing cost (faster changeovers mean less equipment downtime)
  • Smaller lot sizes (faster changeovers enable more frequent product changes)
  • Improved responsiveness to customer demand (smaller lot sizes enable more flexible scheduling)
  • Lower inventory levels (smaller lot sizes result in lower inventory levels)
  • Smoother transition from one part/ product to other (standardized changeover processes improve consistency and quality)


What is Reliability in maintenance?

Reliability, as a concept, is defined as the probability that a component or system will perform a required function for a given time when used under stated operating conditions. To be understood simply, one can say that if an equipment often breaks down unexpectedly, its reliability is very less.

Reliability and Maintenance

Many organization even in today’s time considers maintenance with an approach of ‘fix it when broken’. This is termed as condition based maintenance. But in a manufacturing environment, where quality of production is considered as the actual output, this traditional concept of maintenance poses many challenges. With time, the maintenance approach has also evolved from that of the traditional one. Reliability centred maintenance is the approach that world class manufacturing organizations have adopted.

Through MTBF, we can know the failure rate of an equipment. This failure rate becomes the basis to calculate the reliability of that equipment.

The formula to calculate reliability for the intended time interval:
Reliability for time ‘t’, R(t) = e(-λt)

While this formula gives the current scenario of an equipment, one can set targets of controlling failure by deciding the reliability standard to be met in intended time interval. This in turn helps in devising the maintenance strategy for an organization.

Why is Reliability important?

  • Customer Satisfaction – Reliable assets will perform to meet the customer's needs on time and every time. Thus high reliability is a mandatory requirement for customer satisfaction.
  • Reputation – An organization's reputation is very closely related to the reliability of their services. The more reliable plant assets are, the more likely the organization is to have a favourable reputation.
  • O & M Cost – Poor asset performance will cost more to operate and maintain.
  • Repeat Business – Reliable assets and plant will insure that customer's needs are being met in a timely manner. Customer satisfaction will bring repeat business and also have a positive impact on future business.
  • Competitive Advantage – Many leading and visionary companies have began achieving high reliability / availability of their plants and assets. As a result of their greater emphasis on plant reliability improvement programs, they gain an advantage over their competition.

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