Sometimes referred to as fit and forget maintenance, run to failure is perhaps the most cost-effective of the maintenance strategies, and one that is fairly widely adopted by companies that have a have certain types of equipment or meet other criteria.
Typically, these are infrastructure assets rather than machine-based entities, though it is a strategy that works with cheaper parts which are simply not worth repairing.
Run to failure – also known as RTF – is considered to be an unplanned and, therefore, reactive form of maintenance but in reality, proper run-to-failure can really be a deliberate maintenance strategy that is designed to minimize your maintenance costs. RTF is a credible maintenance strategy under certain circumstances.
There are several reasons why a company would run this type of maintenance plan, including;
- No repair to the equipment is feasible because of design or non-availability of parts.
- It is regarded as a short life asset, such as cheap, high-flow pumps, batteries, or high-traffic doors. Some companies consider that equipment such as fire extinguishers can be placed on RTF list, and that is okay, provided that any statutory checks or expiry dates – most safety equipment has some level of replacement criteria – are noted, possibly on CMMS, and adhered to.
- Disposable Assets – Assets with disposable parts which are intended to be swapped out or replaced rather than repaired. This can include floor and wall surfaces.
- Small assets without significant financial value, such as batteries, and light fittings.
- Non-critical assets such as service and repair tools that can simply be replaced rather than repaired. This could include hand tools and even small electrical devices like multi-meters, provided that suitably calibrated and usable alternatives are available to use.
- Durable Assets – Assets that are not subject to wear or assets that are unlikely to fail inside normal operating criteria. This may include signage and labelling but would not include racking which may fail catastrophically and dangerously.
- Assets that exhibit Random Failure Patterns which cannot be predicted and there is no other choice other than to run to failure.
It can be seen that quite plainly some of these criteria make run to failure an obvious choice; there is no reason whatsoever to routinely replace light bulbs – unless it is a safety issue – in most instances and replacement once they have failed is plainly the best policy.
This kind of maintenance program is a perfectly reasonable method of dealing with the sorts of assets stated above but it should not be confused with have no maintenance policy at all.
However, having a run to failure maintenance policy isn’t perhaps as easy at it may sound, since many parts of your maintenance schedule don’t fail abruptly and some degree of discretion is required.
The lightbulb scenario is credible because a lightbulb is either on or off, and its failure is obvious, but the same cannot be said for other infrastructure elements and equipment.
Flooring may get worn, but at what point is it deemed to have failed and require replacing? Or what about a low-cost machine that makes a noise but still operates as expected. At what point do you decide that it has failed and needs replacing?
Run to failure is usually demonstrated using a bath-tub graph, composed of three distinct sections; introductory failures, normal degradation, and excessive degradation followed by failure.
Typical Run to Failure diagram.
The bath-tub graph depicts the life-cycle of equipment and infrastructure normally considered for a maintenance program such as run to failure, however this type of diagram describes the relative failure rate of an entire population of products over time, rather than single examples of it.
The initial high failure rate can be attributed to infant mortality and ‘burn in’ failures which may be attributed to by a series of defects and blunders, including material defects, design blunders, errors in assembly, which are not caught by the supplier’s quality department and find their way to the customer.
This failure rate will be lower than the ultimate failure area because – ultimately – all of the products will fail and is signified by a period of consistent reduction in failure. Established products may not even have a high mortality rate at fitting, making the left-hand side of the bath-tub curve much flatter.
The middle section of the graph demonstrates the normal operating life of the product, which is still experiencing failures, but at typically a low rate as would be expected during use.
It is in this period that the product can be left to operate unchecked as failures are unlikely and resources can be used elsewhere. The last section of the graph, denoted by a steeply rising curve which represents the end of life pathway of the product, which will eventually see its catastrophic failure.
Failure is usually proceeded by noticeable degradation, culminating in either abrupt failure, or a decision that the product should be stopped or replaced as it is in danger of either causing damage or becoming a safety hazard. It is at this point that the product could be construed to have failed and is replaced.
RTF isn’t a fit and forget policy and is still a maintenance strategy that can be logged and controlled by CMMS and can still be built into a multi-strand maintenance plan.
Obviously, your business will be running a series of maintenance plans, some of which will ensure that expensive and critical equipment is kept running, while other parts of it will consider less critical elements which can be added to a RTF plan. Those areas can be set aside to check at regular intervals – as long as six months even – or even monitored by anecdotal evidence from those in the company who encounter them
While RTF might sound easy, it requires a fairly high degree of expertise to run properly and a good knowledge of the type of equipment used.
It also depends greatly upon the equipment in question and is probably best used in tandem with other strategies so that while all the equipment and infrastructure in you company is covered in some way, it is by a means that is appropriate to its worth, need, or safety requirements.
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