Choosing the right predictive maintenance strategy — or any maintenance approach — depends on your organisation’s goals, risk tolerance, and equipment profile. The wrong choice can lead to unplanned downtime, unnecessary costs, and safety risks. The right strategy, however, can maximise equipment life, improve reliability, and reduce total business costs.
There are three main maintenance strategies every business should understand:
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Breakdown Maintenance (Run to Failure)
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Planned Preventive Maintenance (PM)
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Condition-Based / Predictive Maintenance (CBM or PdM)
In addition to these three strategies, there are many maintenance improvement tactics that can be deployed – things such as Root Cause Failure Analysis (RCA) that seeks to avoid recurrence of (particularly serious) failures, Pro-Active Maintenance (PAM) that investigates current maintenance methods and seeks to optimise them, and Total Productive Maintenance (TPM) that originated in Japanese manufacturing practices and which aims to achieve a culture of motivation and a sense of ownership of equipment, with a focus on the “stitch in time to save nine”. All of these can be thought of as continuous improvement initiatives.
Deciding which is the most appropriate maintenance strategy for each item of equipment is often done fairly casually. A more rigorous approach is to use Reliability Centred Maintenance (RCM), which is a structured technique for identifying the maintenance approach to achieve the inherent reliability level of complex equipment at minimum cost.
In this article, we’ll explore the pros and cons of each and why a predictive maintenance strategy is increasingly becoming the preferred choice across industries.
How to select the best maintenance strategy (including predictive options)
Breakdown maintenance (BD) or run to failure (RtF)
It is the default option. If you do nothing else, you will end up following this strategy. It has the advantage of being easy to understand – you wait until something breaks down and then you fix it – and requiring no mental effort in planning.
Drawbacks of breakdown maintenance
You have no control over when work will be required, and very limited ability to plan resources and spare parts. Since failures generally occur whilst equipment is being used, disruption to production operations tends to be very high. And so often, it seems that failures occur at the most inconvenient time, like a Friday afternoon just as everyone is disappearing for a long weekend. We can summarise this situation as CHAOS.
The need to respond to unexpected breakdowns in a hurry generally results in higher costs – overtime rates for in-house staff, emergency call-out fees for contractors, and urgent freight costs for spare parts.
Running to failure often results in secondary damage to the equipment, making a larger and more expensive repair job.
And disruption to production can cost far more than any maintenance costs – the cost of idle production staff, damaged product, delayed delivery, lost orders and potentially damage to reputation and customer relationships that can multiply the cost well beyond just the immediate loss of product during the repair time.
So, Breakdown Maintenance is normally the most expensive strategy in terms of total business costs.
Planned, preventive maintenance (PM)
It is based on the idea of doing particular tasks on a regular basis (either time-based or run-hours based) with the idea of preventing failures before they occur. The tasks can be pre-planned and scheduled, together with the spare parts, skills, tools and other resources, and ideally scheduled to smooth out resource loads through time. The resulting work can be done efficiently, avoiding having to pay for emergency shipment of materials, or urgent call-out fees for contractors, or excess overtime. And crucially, the timing of the work can be scheduled in with production plans to minimise business disruption.
Adopting a predictive maintenance strategy can help businesses avoid unnecessary downtime by addressing issues before they escalate.
Drawbacks of preventive maintenance
To be valid, a predictive maintenance strategy assumes that specific failure modes will occur at a predictable frequency – eg every 2½ years – so that carrying out the task every 2 years will avoid the problem occurring. However, very rarely do you have sufficient information to know what the optimum frequency is. So you tend to play “on the safe side”, and the result is maintaining more frequently than is really required. This has two negative consequences – firstly it incurs additional cost and downtime, doing work that wasn’t really required; and secondly, every intervention with equipment runs the risk of introducing a fault that wasn’t there before, so it can actually reduce equipment reliability. The number of times equipment fails to start up perfectly after maintenance are so frequent that they are often not even commented on.
In addition, repeated studies have shown that most equipment does not show an increased failure probability with time, but show a random failure pattern. This means that there is no basis for setting a time-based maintenance schedule.
So predictive maintenance strategy is often expensive and ineffective. But it is still the approach many organisations keep trying to follow.
Condition-based maintenance (CBM) or predictive maintenance (PdM)
(Some people differentiate between these two terms; on this site, we use them interchangeably.) It is based on the idea that maintenance work should only be done when you know it is needed. Since the only purpose of maintenance is to avoid failures (think about it), work should only be done when a failure is known to be just about to occur. This means you need a means of detecting whether failures are just about to occur, which is the purpose of Condition Monitoring (CM). Fortunately, most equipment failures don’t just occur instantly with no warning, rather they develop gradually over a period of time. Given the right condition monitoring technique and given the rate of deterioration is not too rapid (in the jargon, the P-F interval is not too short) the result should be that work is only done when it is required, there is no un-necessary maintenance work, and unexpected failures are avoided.
CBM therefore achieves the minimum maintenance cost, minimum downtime (and therefore minimum business cost) and maximum reliability (no unnecessary interventions which could introduce new defects).
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Drawbacks with CBM
- You need an appropriate CM technique that will detect the majority of expected failure modes (eg covering both mechanical and electrical domains).
- Planning needs to be flexible (you don’t have a fixed work plan for the next 1 – 5 years) and thoughtful (combining multiple tasks into one package) to avoid multiple stops and starts to address individual faults one by one.
So, Condition-Based Maintenance is the preferred maintenance strategy if you can adopt an appropriate Condition Monitoring technique
What to do next
If you are interested in applying Faraday Predictive condition monitoring systems to your plant, give us a call on 0333 772 0748, or email us on info@faradaypredictive.com.
If you want to develop your business case for investment in Faraday Predictive condition monitoring systems, take a look at this.
Ready to explore how a predictive maintenance strategy could reduce downtime and costs in your plant? Book your FREE 10-minute demo with Faraday Predictive today.