RAM (Reliability, Availability and Maintainability) Analysis


Along with the glowing size of facilities (i.e. facility’s capacity) and greater demand from the product users on the reliability of product delivery, the effects of unexpected interruptions of facility operation are becoming more and more serious for facility owners. Reliability, Availability and Maintainability (RAM) analysis identifies constituent elements (i.e. equipment) of facilities whose failure affects the facility availability, performing quantitative reliability analysis and proposes effective countermeasures in order to improve the system reliability and maintainability.

The results of RAM analysis provide effective information that is particularly useful in improving the facility plans. The weak points of facilities can be identified objectively and quantitatively, providing a basis for making well-targeted suggestions to enhance availability of the facilities.

Examples of RAM Analysis Implementation

Overall scheme of RAM analysis

An expert experienced in reliability analysis conducts the analysis.
Firstly, the target values for availability, analysis conditions, analysis method and reliability data, i.e. failure rate are confirmed. After finalizing the analysis approach, reliability analysis expert configures the analysis model and conducts the analysis.
Based on the analysis results, TOYO make proposals concerning the facility configuration and maintenance measures to enhance the system availability.

Compilation of analysis results

TOYO will prepare an analysis report describing the facility outline, analysis conditions, failure rate data, analysis results and recommendations.

Extensive experience

TOYO has experiences in RAM analysis for petrochemical plants, fertilizer plants and energy-related plants.

Examples of analysis

  • Target values for availability
  • The target value for availability (96%, for example) is set.

Computation method

  • The availability is computed using Monte Carlo simulation.


Reliability block diagrams are prepared based on the design intentions of the facilities, the configuration of the facilities, the operation mode, equipment capacities and effects of each constituent equipment failure on the entire facility.
The reliability block diagram shows the equipment that makes up the facility in blocks, and connects them either serially or in parallel. When the facility is operational, the right-most edge is reached from the left-most edge via any of the routes. On the other hand, when any of the equipment has failed, the connection is broken at that point. The right-most edge cannot be reached and the facility is shown to be not operational.

Figure-1. Examples of Reliability Block Diagram

Figure-1. Examples of Reliability Block Diagram

Results of availability computation

  • The equipment failure rate and average repair time is applied to each of the blocks in the reliability block diagram, to calculate the availability of the facility.
  • The level of contribution (importance) by each constituent element to the reduction in availability of the facility is obtained.
Figure-2 Availability Computation Results

Figure-2 Availability Computation Results

Table-1. Examples of Criticality Importance

RankingBLOCK No.EquipmentImportance
1BLOCK 1-5Gas Turbine for C-1000B12.36%
2BLOCK 1-6Gas Turbine for C-1000A11.67%
3BLOCK 3-34Service Maintenance10.21%
4BLOCK 3-13Safety Systems8.06%
5BLOCK 1-5V-1200 Electro Static Coalescer2.94%
6BLOCK 3-2C-3000B HP Compressor TrainB2.11%
7BLOCK 3-3C-3000A HP Compressor TrainA2.04%

Discussions of the results

  • The computation result is compared with the target values of availability.
  • Recommendations on the redundancy and /or maintenance for the equipment which contributes to the reduction in availability are made in order to improve the availability of the system.

Results of implementation

  • RAM analysis provides effective information especially for improving new facility plans, and serves as one of the pointers when making investment decisions.
  • The weak points in the facilities, or the equipment that needs to be given priority in preventive maintenance, are identified.