Introduction To Condition Monitoring Techniques
Run-to-failure Maintenance
This applies to non essential equipment and machinery where shutdowns do not affect production, materials and replacement are readily available. It allows the machinery to run to failure and only repair or replace damaged components when the machine comes to a complete stop.
Disadvantages:
- Interrupt production
- Large inventory of spare parts
- Maintenance personnel have to work at odd time and interrupt normal activities and tend to work overtime.
Preventive Maintenance
Preventive or time-based maintenance is to schedule maintenance at predetermined time intervals, based on running hours of machines. In this case replacement of damaged equipment is carried out before problems occur. This allows the machine to run continuously and where the personnel have enough skill, knowledge and time to perform the preventive work.
Disadvantages:
- Performing maintenance tasks either too early or too late
- Replacement of components before the end of residual life
- Reduced production due to unnecessary maintenance
- Possibility of diminished performance due to incorrect repair methods
- Possibility good parts being disassembled and discarded and improper fixing ofreplaced parts can lead to other problems
Condition-based Maintenance
Condition-based or predictive maintenance periodic monitoring involves periodic monitoring on the health of the machine and scheduling maintenance only when a functional failure is detected. This allows trends of the machine component be constructed and time to failure be estimated. Maintenance can be conveniently planned and allows lead-time for organisation of parts and maintenance personnel and be scheduled. This leads to full utilisation of the machine and possible increase in production capacity.
Disadvantages:
- Incorrect assessment of the deterioration of machines
- Inaccurate prediction of the lead-time
- Requires specialised equipment to monitor the trend and highly skilled personnel.
Proactive Maintenance
Proactive or prevention maintenance involves tracing all failures to their root cause and to ensure that failures are not repeated. It utilises predictive/preventive maintenance techniques in conjunction with root cause failure analysis (RCFA). RCFA detects and identify the cause of failure and ensures that proper installation and repair techniques are used. It also identifies need for redesign of machine to avoid future occurrence of the same problems and improve
the reliability of the machine.
Disadvantages:
- Needs highly skill personnel with a vast knowledge of all aspects of maintenance
- May require outsourcing to private consultants and problems with confidentiality
- Requires specialised monitoring equipment and management support