Reliability Modelling for Business Decisions

Introduction Definitions Modelling overview Modelling construction Event graph Results Business Decisions - Questions answered

Reliability The ability of a system or component to perform its required functions under stated conditions for a specified period of time Blanchard, Benjamin S. (1992), Logistics Engineering and Management (Fourth Ed.), Prentice-Hall, Inc., Englewood Cliffs, New Jersey.

Maintainability The measure of the ability of an item to be retained in or restored to specified condition when maintenance is performed during the course of a specified mission profile (The mission-related system maintainability parameter.) 1 1. MIL-STD-721

Availability A measure of the degree of a system which is in the operable and committable state at the start of mission when the mission is called for at an unknown random point in time MIL-STD-721

Availability Inherent availability, A i Achieved availability, A a Operational availability, A o 1. MIL-STD-721

Modelling and Simulation AvailabilityCostMaintenanceConfiguration

Availability Simulation How is a model built? It is built to represent the reliability and maintainability relationships between the items using RBDs Data sources are from engineering drawings and workshops with appropriate people What data is needed?

Building an RBD

Availability Simulation M1 M2 M3

Availability Simulation

Availability Simulation

EG

Availability Simulation

Availability M1 – 92% Availability M2 – 88% Availability M3 – 83% Repair man Utilisation 33% Plant Availability 88%

Questions How many spares used? Which machine caused the most downtime? Are two repairmen required? What about levels of repair? Pro active versus reactive? How is logistic support allowed for?

Questions Where and when is modelling used? – During design to meet requirements and gain financial sign off – During operating phase to determine maintenance and other support tactics – During end of life to determine disposal time and strategy