Reliability Centred Maintenance (RCM)

 

Welcome to the rcm.uk.net web site.

Here you can learn about RCM and download some free RCM utilities for your PC.

 

From this site you can download the following for free:

• RCM Browser Toolbar (for Internet Explorer or Mozilla Firefox)
• RCM Screensavers

 

You may also download a trial version of RCM Desktop software.

 

Click here to be taken directly to the leading provider of RCM training, RCM facilitation and RCM consulting in the UK, Mutual Consultants Ltd.

What is RCM?

 

RCM stands for Reliability Centred Maintenance.

 

RCM may be defined as:

 

“A process used to determine the maintenance requirements of any physical asset in its operating context.”

 

But, if maintenance is defined as ensuring that physical assets continue to do what their users want them to do, then the definition of RCM can be expanded to:

 

“A process used to determine what must be done to ensure that any physical asset continues to do what its users what it to do in its operating context.”

 

 

RCM, i.e. "Reliability-centred Maintenance", is so called because it recognises that maintenance can do no more than ensure that physical assets continue to achieve their built-in capability or "inherent reliability". RCM also recognises that identical assets will have different maintenance requirements in different operating contexts.

A Third Generation Technology

Historically, maintenance has evolved through three generations:

Generations of Maintenance

The first generation covers the period up to World War II, when equipment was simple and often over-designed. During this period maintenance consisted of "fixing it when it broke". The second generation came as equipment became more complex and as pressures on production availability increased during and after World War II. During this period the concept that maintenance actions could prevent failures gave rise to the notion of "preventive maintenance" which in turn led to maintenance planning and control systems. The third generation came in the mid-Seventies. Initiatives outside maintenance (such as JIT in manufacturing, higher product quality requirements, increased awareness of workplace safety and more stringent environmental regulations) are placing increasing pressure on maintenance departments. New research is seriously questioning long-held notions about age and failure and how equipment fails and the use of new techniques (such as condition monitoring) are becoming more widespread.

Equipment Failures

RCM was developed to meet the challenges of the Third Generation in the exacting environment of the civil aircraft industry. Today, every civilian aircraft that flies in the western world has its maintenance requirements determined by RCM before it even leaves the drawing board. Reliability and maintainability are critical in military equipment. As a result, RCM is increasingly being used to determine the maintenance requirements of modern military equipment at the design/procurement stage. Reliability and maintainability is increasingly important in modern manufacturing plant - so much so that many world class companies are using RCM to maximise plant output whilst optimising operating costs.

 

RCM is the approach for ensuring that competitive advantage is maintained and, furthermore, experience has shown that it applies equally to both new and old equipment.

The Seven Basic Questions

 

RCM uses a structured framework to ask the following questions about the selected asset in its operating context:

 

• What are the functions and the associated performance standards of the asset?
• In which ways does it fail to fulfil its functions?
• What causes each functional failure?
• What happens when each failure occurs?
• In what way does each failure matter?
• What can be done to prevent each failure?
• What should be done if a suitable preventive task cannot be found?

 

Briefly, these questions entail:

 

Functions - Defining the Functions and required performance standards of each asset in its operating context. RCM places an emphasis on quantifying the performance standards that are desired from each asset.

 

Functional Failures - Establishing the Functional Failures that apply to each Function. In RCM, a Functional Failure is defined as the inability of an item or component to meet its desired standards of performance.

 

Failure Modes - Determining the Failure Modes that cause each Functional Failure. Failure Modes are the engineering reason why a component or item fails. RCM concentrates on determining the root cause of failure.

 

Failure Effects - Recording the Failure Effects, i.e. documenting what would happen if the Failure Mode occurs. In RCM, the Failure Effects enable the RCM review group members to correctly assess Failure Consequences.

 

Failure Consequences - Categorising the failure consequences of each Failure Mode by considering how much the failure matters. RCM classifies failure consequences into four groups:

 

• Hidden failures, which in themselves have no direct consequences but expose the organisation to the risk of other (often serious) failures
• Safety or Environmental consequences where a failure could hurt or kill someone or lead to a breach of an environmental standard or regulation
• Operational consequences where a failure affects output, product quality, operating costs, or customer service
• Non Operational consequences where the only cost associated with the failure is the direct cost of repair.

 

Predictive and Preventive Tasks - Using a highly developed decision algorithm, each Failure Mode is analysed to determine a suitable Predictive or Preventive Task. RCM selects the tasks only if they can predict or prevent the failure, are technically feasible and are worth doing. RCM defines Predictive tasks as:

 

• On-condition tasks, where an item is left in service on the condition that it continues to meet the desired performance standards
   

RCM defines Preventive tasks as:
 

• Scheduled Restoration where an item is either overhauled/remanufactured regardless of its condition at the time.
• Scheduled Discard tasks, where an item is replaced with a new item at a specified age, regardless of its condition at the time.

 

Default Tasks - Default tasks are determined by RCM if no suitable preventive ask can be found. Default tasks are as follows:

 

• Failure-Finding, which entails checking hidden functions periodically to determine whether they have failed
• Redesign if no suitable preventive or failure-finding task can be found and the consequences and risk of failure are unacceptable
• No Scheduled Maintenance if the cost of a suitable preventive task over time is greater than the cost of rectifying the failure and its consequences.

 

A great strength of RCM is the way in which it provides simple, precise and easily understood criteria for deciding which (if any) preventive tasks are technically feasible and worth doing in any given operating context. RCM also provides a means for deciding how often each task should be done and who should do them.

The People Involved

Maintenance people on their own cannot answer the seven questions posed by RCM. For this reason "Review Groups" are established to apply RCM and hence determine the maintenance requirements of each asset. These groups should include at least one person from the maintenance function and one from the user function. The seniority of the review group members (each of whom will require RCM training) is less important than their knowledge of the equipment under review.

 

Each RCM review group works under the guidance of a highly-trained RCM specialist known as a Facilitator. Their role is to ensure that RCM is applied correctly, that reasonable consensus is achieved by the group and that no significant equipment or component is overlooked. Immediately after each review has been completed, the senior managers with overall responsibility for the assets under review should satisfy themselves that the RCM analysis has been carried out correctly. They need not perform this audit function themselves but may delegate it to anyone in whose judgement they have confidence.

What RCM Achieves

RCM has been used by a wide range of industries for over the past 25 years. When it is correctly applied, RCM yields the following benefits:

 

Safety - greater safety and environmental protection due to:

 

• improved maintenance of existing protective devices
• the systematic review of safety implications of every failure
• the application of clear strategies for preventing failure modes which can affect safety or infringe upon environmental regulations
• fewer failures caused by unnecessary maintenance

 

Performance - improved operating performance due to:

 

• an emphasis on the maintenance requirements of critical equipment elements
• the extension or elimination of overhaul intervals
• shorter maintenance worklists giving less extensive and costly shutdowns
• fewer "burn-in" problems after maintenance by eliminating unnecessary maintenance actions
• the identification of unreliable components

 

Quality - improved quality due to:

 

• a better understanding of equipment capacity and capability
• the clarification of equipment set-up specification and requirements
• the confirmation or redefinition of equipment-operating procedures
• a clearer definition of maintenance tasks or objectives

 

Cost Effectiveness - greater maintenance cost effectiveness due to:

 

• less unnecessary routine maintenance
• the prevention or elimination of expensive failures
• clearer operating policies
• clearer guidelines for acquiring new maintenance technology

 

Life Cycle Cost

 

• reduced life cycle costs by optimising the maintenance workloads and providing a clearer view of spares and staffing requirements

 

Equipment Life

 

• longer useful life of expensive items due to an increased use of On-condition maintenance techniques

 

Maintenance Data - a comprehensive maintenance data base which:

 

• provides a better understanding of the equipment in its operating context
• leads to more accurate drawings and manuals
• allows maintenance schedules to be more adaptable to changing circumstances
• documents the knowledge held by individuals on each piece of equipment

 

Motivation

 

• Greater motivation of individuals, particularly those involved in the review process. This gives improved understanding of the equipment in its operating context and wider "ownership" of the resulting maintenance schedules

 

Teamwork

 

• Better teamwork brought about by the highly-structured group approach to maintenance problem analysis and decision making.

Conclusion

RCM yields results very quickly; most organisations can complete an RCM review on existing equipment and achieve substantial benefits in less than a year. It is also an ideal approach for determining the maintenance requirements of new equipment of all kinds. When applied correctly, it transforms both the maintenance requirements themselves and the way in which the maintenance function as a whole is perceived.

 

Acknowledgement

Thanks to the guys at Mutual Consultants Ltd, the leading providers of RCM training, RCM facilitation and RCM consulting in the UK, for providing this description of RCM, Reliability Centred Maintenance.

 

 

 

 

 

 

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