3 Approaches to Maintenance Strategy

Posted by Jane Lee on November 22nd, 2018

Preventive maintenance has its own merits but as far as maintenance strategies go, it’s not the only one out there. Based on assets, industry, the size and even experience of the maintenance team there are many different approaches that you can employ for manufacturing downtime reduction. Although there are many widely used maintenance management strategies, mentioned below are four most common maintenance strategies, their merits and pitfalls and the circumstances under which they can be applied the best.

Run-to-failure (breakdown maintenance)

Run-to-failure maintenance is a simple maintenance strategy that works best for equipment that can be allowed to operate until they break down. Point reactive maintenance can be performed after the equipment has broken down. However, it should be noted that you must have spare parts and staff in place to replace the failed part and to maintain equipment availability, so that the equipment can be fixed without causing any production issues. This strategy is most effective for equipment, whose breakdown will not create any safety risks and have minimal effect on production. Case in point - a general purpose light bulb, which can be allowed to run until it breaks down. After that it can be fixed or replaced by a new bulb without affecting the production process.

Run to failure maintenance is an excellent strategy when the total cost of repairing the equipment is less than the cost of performing other types of maintenance after breakdown. For example, a machine that runs continuously in a 24/7 production process can be shut down for monthly maintenance. This would stop production and create some disruption. However, keep in mind that all equipment will break down at least once a year. Hence it makes sense to simply repair it when it breaks thus ensuring OEE.

Pros:

a)      Maintenance does not need to be scheduled in advance, which means minimal planning

b)      The strategy is simple, easy to understand and implement

Cons:

a)      Asset failures are unpredictable and is difficult to anticipate

b)      It is inconsistent and therefore might increase the overall cost of maintenance and production  

c)      It increases inventory costs as the staff will need to have spare parts when required 

Predictive maintenance (PdM)

Simply put, predictive maintenance (PdM) predicts when equipment failure might likely occur and to prevent the occurrence of the failure by performing maintenance. It is a condition-based approach, usually linked to a CMMS and generates work orders based on some meter reading gathered by the monitoring device. There are many techniques that can be used for predicting failures, such as vibration analysis, oil analysis, thermal imaging, and equipment observation. Consult with equipment manufacturers and condition monitoring experts to choose the correct technique for performing condition monitoring and ensuring world class OEE.

Assets that are suitable for predictive maintenance must have a critical operational function and have failure modes that can be cost-effectively predicted with regular monitoring.  Assets unsuitable for predictive maintenance usually do not serve a critical function and do not have a failure mode that can be cost-effectively predicted.

Pros:

a)      It ensures that the equipment is only shut down right before imminent failure, which reduces the total time and cost spent maintaining equipment.

Cons:

a)      It increases upfront cost as the cost of the condition monitoring equipment needed for predictive maintenance is often high, as is the skill and experience required to accurately interpret condition monitoring data.

Reliability-centered maintenance (RCM)

Reliability centered maintenance (RCM) is the implementation of a specific maintenance strategy on each of the assets of the facility that aims to optimize the maintenance program of a company or facility. It is a corporate-level maintenance strategy that has four critical principles.

1. Preservation of system function
2. Identification of failure modes that can affect the system function
3. Prioritizing failure modes
4. Controlling the failure modes through selection of applicable and effective tasks

Pros:

a)      It increases equipment availability, and reduces maintenance and resource costs. 

Cons:

a)      It does not consider the total cost of owning and maintaining an asset.