The goal of any maintenance program is to increase uptime, eliminate unexpected failures, maximize asset utilization while taking care of the health and safety of employees and society in general. Reliability Centered Maintenance (RCM) is a strategy that covers all of the above while it aims at maximizing the plant and equipment availability and improving overall equipment efficiency (OEE). RCM also reduces the total cost of ownership (TCO) of plant machinery, equipment, and other assets.
There are four different approaches to maintenance viz., Reactive, Preventative, Condition Based, and Predictive maintenance. The most appropriate choice of course would depend on several factors such as – type of plant machinery or equipment, the criticality of the process deployed in, and the service conditions.
Reactive Maintenance is generally suitable for equipment that is small, low in power (KW) rating, non-critical applications, and in processes where
- a) sufficient redundancy is built into the system,
- b) failure will not lead to serious disruption to production, and
- c) the consequential effects of failure will be minimal and not result in a major loss.
Preventative Maintenance approach is adopted to lessen the likelihood of unexpected failures and works best for plant and equipment whose failure pattern is well established by user experience or the manufacturer and their effective service life is based on usage.
Condition Based Maintenance, as the name suggests is based on the actual condition of the equipment. It is adopted for plant machinery and equipment whose effective life cannot be predicted accurately based on usage data but depends more on the conditions of service and could face random failures. This approach requires an initial investment in setting up an infrastructure for monitoring with instrumentation and personnel with knowledge in monitoring and interpretation of data. But with the advent of remote monitoring technology, organizations are offering this service on a subscription basis and can be accessed without having to commit a huge financial outlay for setting up.
Predictive Maintenance approach is one where techniques such as Failure Mode, Effects and Analytics (FMEA), Root Cause Failure Analysis (RCFA) are applied to predict the time before failure. Maintenance work is planned and undertaken based on these predictions. This approach involves substantial initial investment for monitoring equipment, software, and infrastructure for collection, storage, and analysis of data and personnel specialized in the analytical and prediction techniques. Therefore this approach is applied to plant and machinery that are critical to the process and whose failure could have serious disruption, consequential losses, and sometimes result in catastrophic incidents jeopardizing the health and safety of the wider populace.
Some of the methods adopted for Predictive Maintenance overlaps with that of Condition Based maintenance; for making accurate predictions one needs to assess the condition of the equipment. The condition of the equipment is determined by continuously monitoring certain operational parameters such as the ultra-sonic noise, vibration, and operating temperature in the case of rotating machinery, and NDT methods are employed for the evaluation of others.
The idea behind RCM is to fine-tune the maintenance approach to the needs of the plant and equipment, its application in the industry, the duty cycle, and other such factors rather than following a one-size-fits-all approach. The organization should keep this in mind and choose an approach that renders well to meet its goals and objectives. A well thought out and customized maintenance approach will optimize OEE, aid in reducing costs, and lead to increased profits. RCM is an effective maintenance strategy adopted by leading industries and proven to boost reliability, improve customer confidence and satisfaction.