Shifting Failure Patterns in Reliability Centered Maintenance (RCM)

Question:

Reliability centered maintenance (RCM) helps us predict how components will fail based on 6 common patterns. These patterns include age-related wear, random failures, and infant mortality failures. Is it possible for a component's failure pattern to change after being modified, for example from random to age-related? If so, our aim should be to shift the pattern of most random or infant mortality failures to age-related wear for easier management. Best regards, Rolly Angeles, Educator.

Top Replies

The six failure patterns discussed are a result of a comprehensive study on failures within the airline industry, particularly focusing on data collected from 12 years of failure reports from United Airlines. It is important to note that these patterns may not be applicable across all industries. These patterns have been identified through thorough statistical analysis rather than attributing failures to a single cause. This approach is similar to studying human mortality rates, where patterns emerge based on a large sample size of deaths occurring at different ages. In a complex system with multiple failure modes, certain failure modes may be more prevalent in the early stages of an item's life, while others may manifest later on. For instance, in a new diesel engine, the main journal bearings may experience early failure due to inadequate bedding-in. Once properly bedded-in, these bearings may function effectively for a long period, until eventual wear on the babbit linings leads to failure. It is important to note that in cases where a specific journal bearing fails early on, it can be replaced, thus deviating from the typical failure patterns. In a broader context, various components within the diesel engine may exhibit different failure modes at different stages of its lifespan. Wear and fouling of components such as suction/delivery valves and fuel injectors may occur at varying intervals. While overall engine failure may seem random over time, individual failure modes tend to occur with age. Ultimately, the essence of the phrase "the leopard does not change its spots over time" rings true in the realm of failure patterns and mechanisms.

In John Moubray's book, the 6 failure pattern is thoroughly explored. However, it is worth noting that not all failure patterns are fixed - some can shift from random or infant mortality patterns to a wear out pattern through root cause analysis and part improvement. Transforming these patterns can help make failures more manageable. According to my theory, Total Productive Maintenance (TPM) suggests that accelerated deterioration can progress to a wear out mode through modification. This highlights the importance of modifying patterns to create a more sustainable system. Warm regards, Rolly Angeles, Educator.

In a study involving 100 identical journal bearings under similar operating conditions, it was found that a small percentage of the bearings may experience early failure due to 'bedding-in' issues. Additionally, some failures may occur due to errors made by operators or maintainers, such as poor lubrication or misalignment. The majority of bearings, however, are expected to last a long time and only fail when the babbit metal wears out. To minimize early failures, pre-bedding of journal bearings before installation is recommended. Car-engine manufacturers often conduct a test-run of several hours to ensure proper bedding of engine bearings. While mid-life failures are typically attributed to operational or maintenance issues, steps can be taken to address these issues. Ultimately, the main cause of failure in items like journal bearings is aging. Unlike items like microchips or ball bearings, which fail randomly, complex items with multiple failure modes tend to exhibit a more predictable pattern of failure. By monitoring and replacing components prone to failure, such as ball bearings, equipment can be more effectively managed to prevent age-related failures. This proactive approach, known as Reliability Centered Maintenance (RCM), focuses on identifying and addressing potential failure modes with the use of Condition-Based Maintenance (CBM) and Predictive Maintenance (PdM). It's important to clarify that when discussing random patterns of failure, we are referring specifically to the time of failure, which can be better described as 'exponentially distributed', 'constant hazard', or 'constant conditional probability'. For instance, while a pump impellor getting damaged by a piece of wood is a randomly occurring cause, a ball bearing failure is an event that randomly occurs over time.

Accelerated deterioration, as defined in TPM, is not synonymous with random failure. This type of deterioration is caused by age-related wear, where the rate of wear increases due to a lack of autonomous maintenance practices such as cleaning, lubrication, and checking. By implementing autonomous maintenance (AM), the rate of deterioration can be slowed down, allowing the component to reach its expected lifespan, such as the L10h for ball bearings. This proactive approach helps prolong the life of equipment and prevent unexpected breakdowns.

Accelerated deterioration occurs when age-related wear causes an increase in the rate of wear due to a lack of proper maintenance such as cleaning, lubrication, and checking. As noted in Tokutaro Suzuki's book, "TPM In Process Industries," the failure of a part before its designated lifespan can lead to rapid deterioration. Operating equipment under different conditions can greatly shorten its lifespan and lead to unexpected failures. When faced with accelerated deterioration, it is important to address the issue promptly. Unexpected failures can occur due to negligence, abuse, or random factors. By implementing preventive measures, such as installing screens to prevent foreign materials from causing damage, equipment can be brought back to its normal wear out mode. It is crucial to establish and maintain basic equipment conditions to reduce the risk of accelerated deterioration. By recognizing and addressing root causes of failures, patterns can be altered from random failures to wear out or age-related modes. It is essential to stay vigilant and address issues promptly to ensure the longevity of equipment.

Absolutely, Rolly! Modifications made to a component can definitely change its failure pattern. This could be because the modification either introduces new stresses on the parts causing them to wear down more predictably (thus moving from random to age-related), or it could improve the component's design or quality, reducing the likelihood of infant mortality failures. The challenge lies not only in making a beneficial modification but also in accurately predicting its effect on the failure pattern. Your aim to shift towards age-related wear wherever possible is smart, as it does simplify the planning and execution of maintenance.

Hi Rolly, that's a great question! Based on my experience, a component's failure pattern can certainly shift after modifications. Essentially, changes in the physical properties of the component or different operating conditions can alter its failure behavior. Your suggestion to shift most failure patterns towards age-related wear is interesting. It does make sense as age-related faults are much more predictable and easier to manage. However, we should also consider the cost implications of the modifications needed to produce this change, as they could potentially exceed the benefits of improved predictability. Let's keep on exploring this idea!

More Replies →

Streamline Your Asset Management
See How Oxmaint Works!!

✅   Work Order Management

✅   Asset Tracking

✅   Preventive Maintenance

✅   Inspection Report

We have received your information. We will share Schedule Demo details on your Mail Id.

To add a comment, please sign in or register if you haven't already..   

Frequently Asked Questions (FAQ)

FAQ: FAQs:

Answer: 1. Can a component's failure pattern change after being modified in reliability centered maintenance (RCM)? - Yes, it is possible for a component's failure pattern to change after being modified in RCM. For example, a component's failure pattern may shift from random failures to age-related wear based on modifications or maintenance strategies.

FAQ: 2. How can we shift the failure pattern of components in reliability centered maintenance (RCM)?

Answer: - To shift the failure pattern of components, the aim should be to implement maintenance strategies that promote a transition from random or infant mortality failures to age-related wear. This can involve proactive maintenance practices and monitoring to manage components more effectively.

FAQ: 3. Why is it beneficial to shift the pattern of failures in reliability centered maintenance (RCM)?

Answer: - Shifting the pattern of failures, such as from random to age-related wear, can make it easier to predict and manage maintenance activities. By focusing on reducing random or infant mortality failures and promoting age-related wear, organizations can improve the reliability and efficiency of their maintenance practices.

Ready to Simplify Maintenance?

Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.

Request Demo  â†’