INTRODUCTION

Maintenance can be defined as the process of maintaining, retaining or restoring it to a state in which it can perform a required function which is considered decisive to provide the given service. The course of action could be technical, administrative and managerial. An optimum approach to maintenance is extremely critical because it brings about the most important maintenance objectives such as increasing safety, maximizing equipment life and lowering overall maintenance costs.

TYPES OF MAINTENANCE

Maintenance is categorized into two main categories which are further divided into subcategories. Given below is a chart explaining different types of maintenances which are employed in various industries.

Source:https://www.roadtoreliability.com/types-of-maintenance/

PREVENTIVE MAINTENANCE

The approach of proactively maintaining the assets in working conditions and preventing untimely breakdown can be termed as preventive maintenance. The intention of this type of maintenance is increasing assets lifetime and reducing unscheduled repairs. Preventive maintenance usually combats with the issue that might put the workforce on hold. A classic example of such a strategy would be of a timely scheduling of refiling of the printer in an organization before the ink runs out. In this way, it would not stop the workflow and call the company’s reputation into question. Preventive maintenance schedules may include cleaning, lubrication, oil modifications, corrections, repairs, inspections and replacement components, and partial or total overhauls that are routinely performed

Example of Preventive Maintenance

Change engine oil and oil filter of a car every six months.

Advantages of Preventive Maintenance

      Equipment and building are checked regularly, they are less likely to break down without notice. Hence creating a more secure work environment for employees.

      Tracking of all your facilities at all times and precisely know when your device needs to be replaced.

      Less money is spent because you don’t have to replace equipment as much as last-minute breakdowns.

      There will be far fewer disruptions as all the facilities are well maintained and serviced.

      Reliability of the equipment is greatly increased.

      Productivity is increased as unexpected downtimes are significantly reduced.

Disadvantages of Preventive Maintenance

      It will cost you more to keep the machinery and the structure maintained when you start a preventive maintenance scheme.

      Equipment may not have to be inspected as often as planned leading to over maintenance.

      More workforce is required in case of preventive maintenance as it requires workers to be on-site and perform regular checks

Preventive maintenance is further divided into five sub-categories as follows:

Time-Based

Failure Finding

Condition Based

Predictive

Risk-Based

Time-Based Maintenance

The frequency of maintenance is based on the experience or on the manufacturer’s instructions regarding the equipment. Time-based maintenance involves periodic checking, monitoring and cleaning and replacement of components to avoid sudden failure and process issues. Scheduled maintenance activities like routine checks help identify minor issues before they lead to system failure. Maintenance engineers can identify issues by following periodic, well-designed maintenance timetable. This helps in avoiding long unplanned downtime and makes it possible to perform a repair job in minimum possible time. If these downtimes ever happen, they can be fixed without involving long downtime.

Example of Time-Based Maintenance

In an air conditioner, the air filter needs to be cleaned at regular intervals of time to maintain optimum cooling and maintain its energy efficiency.

In a car, their air filter, fuel filter, brake pads, engine oil, gear oil and brake fluids need to be replaced at definite intervals of time.

Advantages of Time-Based Maintenance

      The higher life expectancy of assets as breakdowns are avoided.

      Lower maintenance costs as time are utilized efficiently and major problems are prevented by regular maintenance.

      Liability is significantly reduced as assets are safely maintained.

      It is cost-effective in many capital-intensive processes.

      It is extremely effective in increasing workplace safety.

Disadvantages of Time-Based maintenance

      Disastrous failures are still probable to happen.

      It is extremely labour-intensive.

      It is not as efficient as maintenance is carried out even if it is not needed.

      Possibility for unintentional damage to components in performing unneeded maintenance.

Failure Finding Maintenance

This type of maintenance is employed to detect machine failures which are not identified in ordinary planned activities. Because failures result from these kinds of hidden faults, condition monitoring or planned maintenance activities are typically not an efficient strategy for maintenance management. Every piece of machinery that has to work in an emergency or as a backup should be subject to failure finding maintenance. These devices or systems are designed to do the following operations.

      Alert

      Relieve

      Shutdown

      Mitigate

      Replace

      Guard

Example of Failure Finding Maintenance

One example would be the machine shut-down pressure switch if the oil pressure drops to a dangerous level. The technician should actually drop the oil pressure to see if it triggers the right response to test this switch.

Advantages of Failure Finding Maintenance

      Can greatly reduce the risk of catastrophic failure.

      Reduces the overhaul frequency

      Reduces the likelihood of sudden equipment failures.

      Focus maintenance on critical system components.

      Increases component reliability

Disadvantages of Failure Finding Maintenance

      Can have major start-up costs for training and equipment needs.

      Management can’t easily see savings potential. 

Condition Based Maintenance

Condition-based maintenance is a maintenance approach that performs maintenance activities depending on your assets ‘ present situation. The condition of the data is known by performing visual inspections, tests and the relevant data gathered by different sensors. These measurements and evaluation will show outcomes that allow diagnosis of the state of the equipment. The maintenance team can, therefore, schedule suitable maintenance actions to avoid failure and ensure regular availability of the equipment The information collected

above demonstrates you when a specific item of machinery may fail so that you can plan maintenance job just before that occurs. The primary objective of condition-based maintenance is to assist you to optimize your maintenance resources by maintaining maintenance work when needed. Some of the common conditions used to measure are mention below:

      Vibrations.

      Temperature

      Pressure

      Oil

      Noise    Understanding the P-F interval and the P-F curve

Source: https://limblecmms.com/blog/condition-based-maintenance/

Example of Condition Based  Maintenance

A sensor could be mounted that measures vibrations of certain rotating equipment. That

the moving piece will degrade with time and begin to fall out of alignment resulting in an increased amount of vibration. Then the mounted sensor can inform when a limit is crossed

by the vibrations so you understand that part of the should be replaced in the future.

Advantages of Condition Based  Maintenance

      The number of unplanned failures is reduced.

      Reliability and availability of equipment are increased significantly.

      Time spent on maintenance is reduced drastically.

      Repairs can be planned during non-peak phases.

      The lifetime of the assets is increased.

      Performance of the assets is increased.

Disadvantages of Condition Based  Maintenance.

      Tools for condition monitoring can be expensive to install.

      You need to spend a lot of time and money training your staff so that they can efficiently use CBM technology.

      Sensors may have trouble working under severe operating circumstances, notably when fatigue damage is observed

      Working in severe operating circumstances can also compromise the sensors, forcing you to regularly replace them, which is often not inexpensive

Predictive Maintenance

Predictive maintenance is a set of operations that detect variations in the state of the machinery to conduct a suitable maintenance job to maximize the service life of the appliances without raising the likelihood of error. Predictive maintenance is a constructive maintenance approach that attempts to estimate when a piece of machinery may fail to perform a maintenance job just before it occurs. These estimates are based on the situation of the machinery being assessed based on the information collected through the use of multiple tools and methods for condition monitoring.

It is categorized into two types based on the methods of identifying signs of failure:

      Condition Based Predictive Maintenance

This type of maintenance relies on regular condition monitoring facilities to identify signs of failure.

      Statistical Based Predictive Maintenance

This type of repair relies on statistical data from a thorough recording of stoppages of in-plant components to develop models for predicting errors.

Example of Predictive Maintenance

When a car is serviced, it is checked whether the alignment of the vehicle suspension is proper or not. This is done to ensure that the tyres make a normal angle with the road. The improper wheel can lead to uneven and premature wear of your tyres

Advantages of Predictive  Maintenance

      The benefits of predictive maintenance from a cost-effective view are enormous.

      Minimizing planned downtime.

      Maximizing equipment lifespan.

      Optimizing Employee productivity and increasing revenue.

Disadvantages of Predictive  Maintenance

      A lot of time taken to asses and implement predictive maintenance schedule.

      Plant staff must be educated on how to use the analytics or data.

      The cost of implementing various predictive tools and the related training is very high.

      Savings potential not readily seen by management.

Risk-Based Maintenance

Risk-based management facilitates maintenance resources to assets that carry the most risk if they fail. It is a technique for the most economical utilization of maintenance resources. This is performed in order to optimize maintenance effort to minimize any risk of failure. The type and frequency of maintenance are given priority depending on the danger of failure. Assets with higher risk and failure implications are maintained and monitored more regularly. Assets that carry a lower risk are subjected to less stringent maintenance programs. Implementation of risk-based maintenance ensures that the total risk of failure is kept to a minimum in the most economical manner throughout the plant.

Source: https://www.fiixsoftware.com/maintenance-strategies/risk-based-maintenance/

Example of Risk-Based Maintenance

An example of this approach will be to replace the components of the machinery that carries the maximum risk if it fails such as brake pads in case of a car.

Advantages of Risk-Based Maintenance

      It defines issues before they occur, minimizing downtime as maintenance can be scheduled.

      When risk-based maintenance is scheduled, reactive maintenance can be avoided, with many overhead costs, more downtime of equipment, higher parts and shipping costs, and more time lost to respond and troubleshoot equipment.

      Improves safety because machinery breaks down less.

      Contributes favourably to company reputation as the adverse effect of machinery failure reaches far down the supply chain.

Disadvantages of Risk-Based Maintenance

      More complex than other types of maintenance

      Parts are replaced before the end of life, which cost more than waiting until they fail.

Corrective Maintenance

Corrective maintenance is described as any maintenance conducted in order to restore machinery to adequate functioning. Due to a breakdown or maintenance recognized through a condition monitoring program, it may refer to maintenance depending on the nature of its use. Due to a breakdown, corrective maintenance could fall under one of two classifications: planned or unplanned. The planned corrective maintenance is the result of a maintenance plan on a run-to-

failure basis. In this case, the maintenance team decided that certain equipment will be serviced when the plan breaks down. Unplanned changes are generally the consequence of accidental failure. For instance, a component machine would break down because of the failure of a replacement component following substitution during routine maintenance.

Advantages of Corrective maintenance

      When corrective maintenance is scheduled as a portion of a maintenance approach, it enables those accountable for reliability to concentrate on other efforts until a breakdown occurs.

      Less capital and staff is required in case of corrective maintenance

Disadvantages of Corrective maintenance

      Decreased productivity due to unplanned downtime of equipment.

      There is a possibility of damage to secondary equipment or process.

Deferred Corrective Maintenance

When scheduling the maintenance of machinery, we accept the impact of failure or malfunction. When we do not have adequate resources to carry out the planned maintenance as expected, these tasks become a backlog or deferred until later. Tasks are delayed when they still have to be done, yet we are waiting for components, properly qualified technicians or required instruments. The maintenance job does not occur when the possibility of failure should be minimized, so deferred. The task may include a new date when it will be completed, but the chance of failure is higher than desired between when it should have been done and when done. The function of deferred maintenance is to balance resources, expenses and accessibility of equipment. Therefore, the deferred maintenance list offers a buffer while maintaining the priorities for the required maintenance operations.

Example of Deferred Maintenance

An example of deferred maintenance would be putting the calibration of measuring devices in the industry due to the shortage of funds.

Advantages of Deferred Maintenance

      The deferred program may be intended to push costs into future periods.

      By implementing a Predictive maintenance program in conjunction with a deferred maintenance program, you can better estimate future costs and even mitigate their impact on your budget.

Disadvantages of Deferred Maintenance

      Increased safety hazards

      Poor service.

      Higher costs in the future

      Inefficient operations

Emergency Maintenance

Emergency maintenance is needed in an industrial environment when life, property, or assets are under instant threat. For example, Emergency maintenance is applied in a processing plant to keep a facility safe and operational. Emergency maintenance protects the health and safety of employees as well as the resources of the building. Returning a facility to full operation as soon as possible is essential for a company’s continued viability, profitability, and enhancing public perception of the responsiveness of the company.

Advantages of Emergency Maintenance

      A lack of initial costs involved in the first key advantage to run a reactive maintenance system.

      The strategy needs fewer employees to handle a portfolio or client due to the decreased planning, management and organizational time engaged in emergency maintenance.

Disadvantages of Emergency maintenance

      One of the major drawbacks of reactive management is the unpredictability of when problems may arise.

      This type of maintenance does not protect or care for equipment, thus reducing the lifetime of the unit.

      This type of maintenance could lead to catastrophic failure inside the facility.

      Indirect expenses are identified with reactive servicing with machinery downtime or unreliable machinery that has adverse impacts on reputation, safety and company efficiency.

Conclusion

In a nutshell, I would like to state that preventive maintenance is leaps and bounds ahead of corrective maintenance. Catastrophic disaster and failures could be avoided if good preventive maintenance techniques are put into perspective. Apart from avoiding complete failure, it can also increase productivity, increase efficiency, decrease downtime and increase safety within the facility. Preventive maintenance techniques such as time-based maintenance keep the facilities and equipment in an optimum condition. Preventive maintenance techniques such as predictive maintenance provide the average mean life of tools so that they can be replaced before failure.

REFERENCES

      https://www.onupkeep.com/learning/maintenance-types/scheduled-maintenance

      https://www.roadtoreliability.com/types-of-maintenance/#failure_finding_maintenance

      https://limblecmms.com/blog/condition-based-maintenance/

      https://www.reliableplant.com/Read/12495/preventive-predictive-maintenance

      https://www.fiixsoftware.com/corrective-maintenance/

      https://accendoreliability.com/basics-planned-deferred-maintenance/

      https://specialties.bayt.com/en/specialties/q/204305/what-is-the-advantages-and-dis-advantages-for-the-emergency-maintenance-plane-due-to-the-increase-of-the-profit-margin/

      https://www.fiixsoftware.com/breakdown-maintenance/