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Reliability, Availability and Maintainability (RAM) Modelling

Reliability, Availability and Maintainability (RAM) study is a structured and quantitative approach implemented for asset optimization and work on the Monte-Carlo principle to significantly lower project costs. The objective of the RAM modeling and simulation is to highlight all possible causes of production losses and suggest the best system alternatives. It is a probabilistic approach and work on the Monte-Carlo principle. Thus, the RAM study is a tool for decision-making and optimizing the system by altering specific parameters in the design or it’s logistic to achieve maximum cost-efficiency.

The figure explains the relationship between Reliability (R), Availability (A) and Maintainability (M) and their definition. From the figure and the definition, it is clear that a system will perform optimal when these factors are considered into the design and operation of the system. Hence a proper RAM analysis will result in achieving maximum system ability as per its design. Consequently a better decision for productivity, services utilization, maintenance and functioning of equipment are implemented.


The RAM study and analysis is generally performed during the FEED stage of the project. However, it can be reviewed and updated as the complexity of project increases with the progress. But this update of the system during the later stage should not impact the project cost. As mentioned, the main significance of RAM analysis is to evaluate the causes of loss of operational availability or issues that may limit the production throughput and suggest improvement.

The main points considered during the RAM study of a system is mentioned below:

  • Evaluation of equipment reliability and redundancy
  • Maintenance and mobilization strategy
  • Failure rate
  • System productivity
  • System assessment

Common Issues

  • Process/System not meeting the production targets
  • Excess cost for achieving the production efficiency
  • Unavailability of cost – effective maintenance plan
  • Redundant equipment
  • Over-design of the system
  • Spare parts management for maintenance


The benefits of undertaking a RAM Studies include:

  • Better management of maintenance and spare parts, leading to increase/maintain the production levels;
  • Advance contingency plans for any unscheduled or scheduled outage;
  • Investment optimization by highlighting the redundancy;
  • Accurate prediction of the equipment life-cycle;
  • Identification of the critical equipment for the production

In short the RAM modelling for a given system is performed in following steps

  • Functional Analysis
    • Determination of functional diagrams
    • Cause and Effect Analysis
  • Selection of Quantitative data
    • Selection of reliability data
      • Plant data, OREDA data etc.
    • Selection of operational data
      • Basis of design/Philosophies
  • Assessment of production availability
    • Building of Reliability block diagram (RBD)
      • Maintenance strategies-operational philosophies
    • Production availability calculation
      • Modelling and Simulation
      • Analysis
    • Conclusion and recommendation
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