The ability of a machine, line or system to perform at the required level throughout its life is largely “baked-in” when it’s designed. The decisions taken here determine overall reliability, how much maintenance it will need, how long that maintenance will take to perform and even the life of the asset.
Reliability availability maintainability analysis (RAM analysis) is a tool for first optimizing equipment durability and performance and then for identifying ways of making improvements. This blog introduces the concept, discusses the role of RAM in maintenance and offers some guidance for implementation.
What is reliability, availability and maintainability (RAM)?
RAM is a tool for quantifying the factors that determine the productive ability of a manufacturing asset and identifying improvement opportunities. This is achieved by optimizing how it is both designed and maintained.
As a key part of asset lifecycle management and reliability-centered maintenance, periodic RAM analysis helps manufacturers adjust the type, amount and frequency of maintenance being performed. The goal in this is to reduce total costs associated with the asset. This can involve trade-offs in both design and maintenance, and a RAM analysis provides a framework for making these decisions in an informed way. The result of a successful RAM analysis exercise should be improved performance of complex industrial systems.
Components of RAM
A reliability, availability and maintainability analysis requires measuring or, in the case of equipment still in design, estimating each of these three components.
- Reliability: This is the inverse of the probability of failure or the probability of not failing. For existing equipment, reliability can be determined from Mean Time Before Failure (MTBF). In the case of equipment being designed, Failure Mode Effect Analysis (FMEA) can predict the most likely failures. Following up with Fault Tree Analysis and Reliability Block Diagrams will identify aspects of the design needing further attention.
- Availability: This is a measure of the proportion of time in a given period over which the equipment could run, if needed. While 100% would be ideal, even if there are no breakdowns, preventive maintenance (PM) will eat into available time.
- Maintainability: Some equipment is easier to maintain than others. This is measured by Mean Time To Repair (MTTR). MTTR is calculated as: (Total time spent performing maintenance work) / (Number of times work was needed).
Reliability vs. availability
These two components of RAM overlap: if a machine is unreliable, availability is likely low. However, this implies significant MTTR, which illustrates the difference between the two.
Reliability is the probability that a machine or piece of equipment will not fail during a defined period of time. It is derived from the inverse of MTBF. (A larger MTBF suggests a lower probability of failure in a given period.)
Availability is the time for which equipment is ready to run, regardless of whether it is actually run. An availability percentage can be calculated from: MTBF / (MTBF + MTTR).
Thus, if MTTR is short, meaning the maintainability of a machine is good, availability can still be high even with poor reliability.
Availability is similar to machine uptime, except uptime refers to when a machine is actually running. Uptime starts when the machine or line begins running and ends when the order is complete, whereas availability includes time waiting for resources.
Steps to implement RAM in manufacturing
When applied during equipment design, RAM can identify changes to improve reliability and maintainability. However, applying RAM maintenance can increase availability, reduce machine downtime and extend asset life. The process is:
- Assessment and planning: Select a target for the analysis. Evaluate current systems and identify improvement opportunities.
- Data collection and analysis: RAM requires data on system performance, much of which should be available from reliability monitoring results stored in the CMMS. Use this data to develop strategies that will improve reliability, availability and maintainability.
- Implementation: Apply the developed RAM strategies to manufacturing processes, following up with continuous monitoring and improvement. Look for ways to improve how RAM analyses are conducted.
RAM tools and techniques
Data on reliability, availability and maintainability will provide insights into improvement opportunities. For greatest effectiveness, however, the following four tools and techniques should be used:
- Failure modes and effects analysis (FMEA): Primarily a design tool, FMEA can also be applied to existing equipment. In both cases the goal is to identify and prioritize potential failure modes, then determine appropriate corrective and preventive measures.
- Root cause analysis (RCA): This structured process helps avoid leaping to conclusions about the reasons for failures. RCA tools include 6 Ms, 5 Whys and fishbone or Ishikawa diagrams.
- Reliability-centered maintenance (RCM): This provides a way of prioritizing maintenance activities based on equipment reliability and criticality. RCM will, for example, lead managers to apply different maintenance strategies to individual pieces of equipment.
- Predictive maintenance: This uses data and analytics to predict and prevent failures, with the goal of increasing availability through less downtime, while also extending MTBF.
Benefits of implementing RAM in manufacturing
Low machine reliability, availability and maintainability reduce effective capacity and constrain output. RAM analyses help managers evaluate the trade offs often encountered when trying to improve each element individually. This leads to:
- Increased efficiency: Reliable equipment with high availability increases operational efficiency.
- Reduced downtime: Unexpected breakdowns and maintenance are minimized.
- Cost savings: Better reliability means less time spent on corrective maintenance and lower operational costs.
- Improved safety: Unreliable equipment resulting in repeated stoppages becomes a safety hazard for workers. Improved reliability means better workplace safety.
Help for your reliability improvement efforts
Adopting a RAM approach improves maintenance effectiveness and leads to operational improvements. RAM should begin at the equipment design stage but can still be applied to lines, systems and machines already in service. The keys to successful implementation are to select appropriate targets, gather and analyze maintenance data and implement identified improvements.
ATS helps manufacturers improve the effectiveness of their maintenance operations. Our services range from short term support to assistance with implementing reliability-centered maintenance and a range of predictive maintenance solutions. Contact us to learn how we can help.
