The ReliabilityBlockDiagram(RBD) is used to identify potential areas of poor reliabilityand where improvements can be made to lower the failure rates for the equipment. This method can be used in both the design and operational phase to identify poor reliabilityand provide targeted improvements. Understanding the Reliability Block Diagram Was this helpful? Block Diagram in Excel | Design Systems Reliability - depicts the effect of a component failure on the system's function. To Create a Block Diagram. Lay out a diagram of parallel and serial components; Identify probability of failure of each component (value 0-1). Calculate parallel probabilities. (a+b-a*b) Multiply serial component probabilities (a*b) Use parallel parts to increase reliability.[PDF] Reliability Block Diagram (RBD) A reliability block diagram (RBD) is a drawing and calculation tool used to model complex systems. An RBD is a series of images (blocks) representing portions of a system. Once the images (blocks) are configured properly and image data is provided, the failure rate, MTBF, reliability, and availability of the system can be calculated.