RCM: THE SEVEN BASIC QUESTIONS

The RCM process entails asking seven questions about the asset or system under review, as follows:

1. what are the functions and associated performance standards of the asset in its Present operating context?
2. in what ways does it fail to fulfill its functions?
3. what causes each functional failure?
4. what happens when each failure occurs?
5. in what way does each failure matter?
6. what can be done to predict or prevent each failure?
7. what should be done if a suitable proactive task cannot be found?

Before it is possible to apply a process used to determine what must be done to ensure that any physical asset continues to do whatever its users want it to do in its present operating context, we need to do two things: predictive maintenance preventive maintenance failure-finding change the design or configuration of the system change the way the system is operated run-to-failure

• determine what its users want it to do


• ensure that it is capable of doing what its users want to start with

This is why the first step in the RCM process is to define the functions of each asset in its operating context, together with the associated desired standards of performance.

The objectives of maintenance are defined by the functions and associated performance expectations of the asset under consideration. The only thing likely to stop any asset performing to the standard required by its users is some kind of failure. This suggests that maintenance achieves its objectives by adopting a suitable approach to the management of failure.

Therefore, before we can apply a suitable blend of failure management tools, we need to identify what failures can occur. The Ivara RCM2 process does this at two levels:

• firstly, by identifying what circumstances amount to a failed state then by asking what events can cause the asset to get into a failed state


• in the world of RCM, failed states are known as functional failures because they occur when an asset is unable to fulfill a function to a standard of performance which is acceptable to the user

In addition to the total inability to function, this definition encompasses partial failures, where the asset still functions but at an unacceptable level of performance (including situations where the asset cannot sustain acceptable levels of quality or accuracy). Clearly these can only be identified after the functions and performance standards of the asset have been defined.

Once each functional failure has been identified, the next step is to try to identify all the events which are reasonably likely to cause each failed state (or failure modes). . "Reasonably likely" failure modes include those which have occurred on the same or similar equipment operating in the same context, failures which are currently being prevented by existing maintenance regimes, and failures which have not happened yet but which are considered to be real possibilities in the context in question.

Most traditional lists of failure modes incorporate failures caused by deterioration or normal wear and tear. However, the list should include failures caused by human errors (on the part of operators and maintainers) and design flaws so that all reasonably likely causes of equipment failure can be identified and dealt with appropriately. It is also important to identify the cause of each failure in enough detail to ensure that time and effort are not wasted trying to treat symptoms instead of causes. On the other hand, it is equally important to ensure that time is not wasted on the analysis itself by going into too much detail.

in identifying failure effects, include all the information needed to support the evaluation of the consequences of the failure, such as:

• what evidence (if any) that the failure has occurred
  
  
• in what ways (if any) it poses a threat to safety or the environment
  
  
• in what ways (if any) it affects production or operations
  
  
• what physical damage (if any) is caused by the failure
  
  
• what must be done to repair the failure

The process of identifying functions, functional failures, failure modes and failure effects yields surprising and often very exciting opportunities for improving performance and safety, and also for eliminating waste in the maintenance process.

The Result? A detailed analysis of an average industrial undertaking is likely to yield between three and ten thousand possible failure modes. Each of these failures affects the organization in some way, but in each case, the effects are different. They may affect operations. They may also affect product quality, customer service, safety or the environment. They will all take time and cost money to repair.

It is these consequences which most strongly influence the extent to which we try to prevent each failure. In other words, if a failure has serious consequences, we are likely to go to great lengths to try to avoid it. On the other hand, if it has little or no effect, then we may decide to do no routine maintenance beyond basic cleaning and lubrication.

A great strength of Ivara RCM2 is that it recognizes that the consequences of failures are far more important than their technical characteristics. In fact, it recognizes that the only reason for doing any kind of proactive maintenance is not to avoid failures per se, but to avoid or at least to reduce the consequences of failure.

The Ivara RCM2 process classifies these consequences into four groups, as follows:

1. Hidden failure consequences: Hidden failures have no direct impact, but they expose the organization to multiple failures with serious, often catastrophic, consequences. (Most of these failures are associated with protective devices which are not fail-safe.)
2. Safety and environmental consequences: A failure has safety consequences if it could hurt or kill someone. It has environmental consequences if it could lead to a breach of any corporate, regional, national or international environmental standard.
3. Operational consequences: A failure has operational consequences if it affects production (output, product quality, customer service or operating costs in addition to the direct cost of repair)
   
4. Non-operational consequences: Evident failures which fall into this category affect neither safety nor production, so they involve only the direct cost of repair.

The Ivara RCM2 process uses these categories as the basis of a strategic framework for maintenance decision-making. By forcing a structured review of the consequences of each failure mode in terms of the above categories, it integrates the operational, environmental and safety objectives of the maintenance function.

This helps to bring safety and the environment into the mainstream of maintenance management.

The consequence evaluation process also shifts emphasis away from the idea that all failures are bad and must be prevented. In so doing, it focuses attention on the maintenance activities which have most effect on the performance of the organization, and diverts energy away from those which have little or no effect. It also encourages us to think more broadly about different ways of managing failure, rather than to concentrate only on failure prevention. Failure management techniques are divided into two categories:

• proactive tasks: these are tasks undertaken before a failure occurs, in order to prevent the item from getting into a failed state. They embrace what is traditionally known as 'predictive' and 'preventive' maintenance, although we will see later that RCM uses the terms scheduled restoration scheduled discard and on-condition maintenance
• default actions: these deal with the failed state, and are chosen when it is not possible to identify an effective proactive task. Default actions include failure-finding, redesign and run-to-failure

The users of the assets are usually in the best position by far to know exactly what contribution each asset makes to the physical and financial well-being of the organization as a whole, so it is essential that they are involved in the RCM2 process from the outset.

Done properly, this step usually takes up about a third of the time involved in an RCM2 analysis. It also usually causes the team doing the analysis to learn a remarkable amount about how the equipment actually works.