RAM is a characteristic of a system’s long-term operation and quality of service. It is achieved by the application of established engineering concepts, methods and tools throughout system development life cycle. The RAM can be characterised as a qualitative and quantitative indicator of the degree that the system, or its sub-systems and components, can be relied upon to function as specified and be available over a period of time.
Proven and structured RAM techniques are used during various phases of system, to ensure that its performance objectives are met. It is used to minimise system downtime and costly repairs.
RAM engineering is widely used in various industries around the world, including Transport, Aviation, Space, Defence etc. According to EN50126 (Railway Applications. The Specification and Demonstration of Reliability, Availability, Maintainability and Safety)
RAM elements are defined as:
Reliability: Ability of an item to perform a required function under given conditions for a given time interval.
Availability: Ability of a product to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval assuming that the required external resources are provided.
Maintainability: Ability of an item under given conditions of use, to be retained in, or restored to, a state in which it can perform a required function, when maintenance is performed under given conditions and using stated procedures and resources.
Reliability and Maintainability are design characteristics of an asset and can be optimised (using methods such as such as redundancy, diversity, remote condition monitoring, modular design etc) to achieve better efficiency and improved system availability. This, in turn, can result in:
1. Lesser system failures
2. Reduced downtime
3. Improved ‘Whole of Life’ cost
4. Improved safety
5. Lesser penalties (due to delayed/cancelled services or production losses)
Common RAM analysis tools that are used to support system development are given below:
• Failure Modes, Effects and Criticality Analysis (FMECA)
• Fault Tree Analysis (FTA)
• Reliability Block Diagram (RBD)
• Spare Parts Analysis
• Common Cause Failure Analysis
• Cause and Effect Analysis (Fishbone Diagram)
In addition to the functional performance, RAM plays a key role in Lifecycle Costing Analysis and Safety Analysis.
Our systems engineering team is competent in the determination and application of RAM management procedures and techniques on complex projects.
Author: Vikas Sharma, Management Commercial Engineering Ltd