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Reliability, Availability and Maintainability (RAM) Analysis

Objective of RAM Analysis:

Reliability, Availability, and Maintainability (RAM) are system design attributes that can have a substantial impact on the lifecycle cost and performance of an engineered system. The purpose of RAM Analysis is to ensure high production performance while maintaining high safety and quality level in any given industrial operation.

The objective of the RAM analysis is to provide decision support towards i.e.:

  • Predicted production performance and project economics;

  • Key production loss contributors;

  • Maintenance strategy and spare part philosophy;

  • Alternative technical or operational solutions (sensitivity studies);

  • Main uncertainties related to production performance;

  • Recommendations for improved production performance.

Methodology for RAM Studies:

At its core, RAM studies entail representing a complex reality with a simplified model allowing for various types of analyses. Such a model can be used to predict performance and manage uncertainties. Results from the analyses should be used to give sound and unbiased decision support, as well as identify bottlenecks and main contributors to reduced performance and/or increased risk.

1.Establish study basis

Identification of key assumptions and associated degrees of uncertainty is considered vital in order to effectively produce as realistic and accurate results as possible, and for giving input to sensitivity analyses that might be necessary to cater for uncertainties. The key assumptions will be documented in the RAM model study basis. Assumptions are typically categorized in technical, operational and analytical assumptions.

Close cooperation with different disciplines in the project is necessary to ensure an understanding of the process and operation that results in a robust and realistic basis for the RAM model. Because of this, it is proposed to arrange for a work meeting or similar with relevant disciplines when establishing the RAM model study basis.

2.Required Input

A good understanding of the system to be analysed is important for the RAM analysis to obtain as accurate results as possible. Typical client input for RAM analyses include:

  • System description;

  • System schematics;

  • P&IDs;

  • Operational Philosophy.

In addition to the above, one of the main premises for performing a successful RAM analysis is the use of appropriate reliability data. Application of data from literature and databases should always be thoroughly evaluated, to validate their relevance for the context in question. Reliability data sources include client experience data, OREDA and the PDS handbook. ORS has access to a wide range of reliability data sources. 

A Failure Mode, Effect and Criticality Analysis (FMECA) if available is also a good input for the RAM analysis, especially for complex systems to give an accurate basis for system modelling.

3.Establish RAM model and run simulations

The RAM model study basis is used to establish the RAM model, typically represented by reliability block diagrams (RBDs). The Monte Carlo method is normally used for the RAM model simulations to produce uncertainty ranges and confidence levels for the estimates. ORS uses the software Miriam RAM Studio for this purpose. 

4.Analyse the results

The results from the simulation are analysed and reported depending on the objective of the RAM study in the best way to create value to the client, ,with some examples shown below.

Success rate probability distribution

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