Probability and Redundancy

Overview:

Process plants are striving now more than ever to reduce operational expenditures while increasing productivity and efficiency. Today's process engineers place a tremendous amount of emphasis on system integrity requirements. Why? Because it's a variable that can be controlled when the right equipment is in place.

System Integrity Requirements
System integrity: State of a system where it is performing its intended functions without being degraded or impaired by changes or disruptions in its internal or external environments.

System reliability is a calculation based on estimates. Certain procedures and component evaluations are used to predict the integrity of a given system or individual component. Each component of a system is evaluated individually and its probability of failure is estimated. The manner in which components are connected will influence the integrity of the system. For example a system component connected in series will have more probable impact on the system integrity than a more reliable parallel connection. Each component estimates are combined to provide an over all estimate to the probability of failure for a given system. Redundancy is used to add to the systems overall availability and reduce a given systems probability of failure.

Parallel Redundancy
Two or more system components are operating simultaneously. Only one component is required to be working for the system to operate, and it should continue to function at acceptable performance levels after the loss of any component. Both components must fail in order for a system failure.

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