Reliability Block Diagram
A reliability block diagram is a visual model showing how component success or failure affects the ability of a system to perform its required function.
What this term means in maintenance
A reliability block diagram is a visual model showing how component success or failure affects the ability of a system to perform its required function.
How an RBD works
Blocks represent required components or functions. Their arrangement shows the system logic.
- Series arrangement: every block must succeed
- Parallel arrangement: one or more alternate paths can preserve the function
Practical example
A water-supply system contains two parallel pumps followed by one common control valve. Pump redundancy improves reliability, but the common valve remains a single point of failure.
What RBDs support
They can help teams:
- Understand system dependencies
- Identify single points of failure
- Compare redundancy options
- Estimate system reliability
- Review maintenance and spares strategy
Difference from fault tree analysis
An RBD models the success paths required for the system to function. Fault tree analysis starts with an unwanted event and maps causes of failure.
Common mistake
Ignoring shared utilities, controls, and common-cause failures can make the diagram appear more reliable than the real system.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Single Point of Failure
A single point of failure is one component, asset, or function whose failure can stop the entire required system because no effective alternative exists.
Redundancy
Redundancy is the provision of additional equipment, components, or paths so a required function can continue when one element fails.
Fault Tree Analysis
Fault tree analysis is a deductive method that starts with an unwanted event and maps the combinations of equipment, process, control, or human failures that could cause it.
Glossary FAQs
- What is a reliability block diagram?
A model showing how component success or failure affects system function.
- What is a series arrangement?
Every block must succeed for the system to work.
- How is an RBD different from a fault tree?
An RBD models success paths; a fault tree maps causes of an unwanted event.