Understand the differences of reactive, preventive and predictive maintenance strategies

Understand the differences of reactive, preventive and predictive maintenance strategies

By setting a maintenance strategy for its assets, an organization and the person in charge, does it with a purpose in mind.

Possible reasons include:

– Prevent breakdowns or failures, in order to maximize the useful life of the machinery;
– Increase machine reliability so its operation is continuous and efficient;
Minimize production loss and meet deadlines for customers;
Comply with job safety regulations for collaborators;
Reduce costs and manage risks in general.

A maintenance plan will include various maintenance strategies, according to what is most cost-benefit for a particular asset. Although its common to split the different maintenance approaches – reactive (run to failure), preventive and predictive – it shall be taken into account that each machine may need a mix of those interventions.

The most appropriate mix will be set considering the potential losses of production stops for the specific machinery, its repair cost, environmental impact, people safety and product or service quality, among others.

There are advantages and disadvantages in all maintenance strategies, so nothing better than the maintenance engineering specialist and the strategic leadership of shop floor to  put together a plan according to the asset portfolio. Team work between the maintenance engineering and operation management is essential in the planning and definition of most appropriate maintenance interventions.

Reactive (Run to Failure) Maintenance

Run to failure, as the name indicates, implies that machine repairs are performed only after a failure occurs. Therefore, it is called reactive. The machinery has failed or the wear has been such that it needs intervention in order to return to fulfill its normal operational function.

It is the maintenance strategy applied when it is believed that the production stop and repair costs in case of failure will be less than the investment required for a scheduled maintenance. This strategy may be cost-effective until a catastrophic failure occurs.

Advantages and disadvantages of preventive maintenance

Preventive maintenance is the one that follows an earlier planning, based on defined time intervals or according to a pre-established criterion, in order to reduce the risk of machinery failure or performance drop. Also known as Time Based Maintenance (TMB).

Some advantages of preventive maintenance:

Reduction of machine failure or production process stoppages;
Increased asset and industrial plant useful life;
Economies by saving materials, spare parts and labor time through planning;
– Reduction of energy consumption with machines running efficiently;
Flexibility that planned interventions allow to accommodate other tasks;
Improved safety for the workers.

Some the disadvantages of preventive maintenance:

There are still risks of unexpected stoppages or breakdowns;
It is workforce intensive;
Risk of damaging parts by performing unnecessary maintenance;
Difficulty to set the time intervals for maintenance intervention;
Savings are only mensurable on medium to long-term.

Predictive maintenance or reliability-based maintenance

Predictive maintenance uses techniques and instruments to monitor the machine condition or health, its performance and potential failure indicators, in order to carry out specific maintenance actions at the right time and at the lowest possible cost.

Sometimes also defined as a high availability maintenance strategy for critical machinery that shall not fail or break. Those are machines whose availability is required to be above 90% which is justified by serious consequences in case of unavailability or failure.

The high demand for the machine is an indicator that it must be monitored constantly and its maintenance performed in a predictive manner.

Another contribution of condition based maintenance is the possibility of identifying random failures, which represent approximately 80% of failure patterns. In these cases the continuous condition monitoring proves to be effective.

Some advantages of predictive maintenance:

Increase useful life of the asset and its components;
Cost reduction with spare parts and maintenance labour hours;
Improved safety and productive environment;
Maximize asset productivity;
Reduction of the cost of production costs;

Some disadvantages of predictive maintenance:

Requires qualified workers with data analysis capabilities;
Investment in equipment for diagnosis added to the costs to run the program;
Requires strong management commitment.

It is worth repeating that the universe of industrial equipment is very broad and the criticality and availability that each specific asset has in the production process requires specific analysis and the establishment of the best approach.

New technologies will help the industry 4.0 to be more effective in its maintenance processes as well. It is possible that the continuous monitoring of the machine health o is still infrequent due to the lack of cheap and efficient solutions to measure relevant parameters such as vibration, temperature, pressure, etc.

DynaPredict is an industry 4.0 solution that integrates these technological advances into a wireless data logger with acceleration and temperature sensors. Simple, efficient and affordable. It produces a true ‘movie’ of the machine condition, for the time your company deems appropriate.