An Efficient Failure-Based Maintenance Decision Support System for Smalland Medium Industries - Efficient Decision Support Systems: Practice and Challenges from Current to Future - page 198

According to Palmer (1999), if the plant spends a lot of time on breakdown maintenance,
then it does not spend enough time on preventive maintenance. Thus, predictive
maintenance is introduced to resolve deficiencies with scheduled downtime. Predictive
maintenance involves monitoring certain conditions or variables associated with the
equipment (Bentley, 1993). The simplest method of condition-based monitoring involves the
four human senses of sight, sound, touch and smell to predict a failure. Repairing activities
take place when the condition shows that a failure may be imminent.
Unlike the Condition-based Maintenance (CBM) policy, in predictive maintenance the
acquired controlled parameters data are analyzed to find a possible temporal trend. This
makes it possible to predict when the controlled quantity value will reach or exceed the
threshold values. The maintenance staffs will then be able to plan when, depending on the
operating conditions, the component substitution or revision is really unavoidable. The
following main activities can help to avoid machine breakdown (Bentley, 1993):
i. Fault detection,
ii. Fault isolation,
iii. Fault elimination, and
iv. Verification.
The same was demonstrated by Geert and Liliane (2004), who distinguished five basic
maintenance policies in corrective and preventive maintenance. Preventive maintenance is
carried out using a planned, periodic and specific schedule to keep a machine in a stated
working condition, throughout the process of checking and reconditioning. Preventive
maintenance is defined as the pre-breakdown model performed on equipment to either
eliminate or reduce the emergency failures within pre-determined economic limits (Lewis,
1999). The model has been introduced to enhance reliability and confidence of the machine
in advance. This maintenance is categorized as proactive maintenance. The service is
repeated at a pre-determined frequency to avoid any unplanned breakdown of the machine.
Bentley (1993) divides the preventive maintenance (PM) model into CBM with two main
categories, as follows:
i. Monitored PM, which involves monitoring when the machine is in operation. Triggers
on any potential failure will be detected. Repair activities are to be conducted before
any unplanned breakdown; and
ii. Scheduled maintenance, where the service is being conducted on the same machine at
specific counter or time intervals. The maintenance crew always follows the standard
checklist to conduct PM activities, which involves scheduled replacement of parts,
service, alignment, greasing, lubrication, confidence testing, etc.
Geert and Liliane (2004) distinguished five basic policies in maintenance, as follows:
i. Failure-based Maintenance (FBM);
ii. Use-based Maintenance (UBM);
iii. Condition-based Maintenance (CBM);
iv. Detection-based Maintenance (DBM); and
v. Design-out Maintenance (DOM).
They have suggested seven steps to follow in a modular framework on maintenance
policies, before building any maintenance policies, as follows:
i. Identification of the objectives and resources,
ii. Selection of the most important maintenance systems,
iii. Identification of the most critical machines and their components,