Standby Redundancy, Equal Failure Rates, Imperfect Switching

Standby Redundancy, Equal Failure Rates, Imperfect Switching

First off, switches are not perfect, so this situation includes the reliability of the switch. Switch reliability may be a factor of storage time, probability of actually working when called on to work, or number of switching cycles. Each switch technology may be slightly different. For this equation, you need the reliability or probability of success given the primary unit has failed. Although we are assume the switch reliability is independent of the primary unit reliability and subsequent failure.
Continue reading

Standby Redundancy with Equal Failure Rates and Perfect Switching

Standby Redundancy, Equal Failure Rates, Perfect Switching

First off, switches are not perfect, so this situation is hypothetical. Yet, when you are exploring adding standby redundancy and haven’t sorted out the switching mechanism, you may be purely curious about the benefits of the redundancy. Continue reading

Reliability Block Diagrams Overview and Value

Reliability Block Diagrams Overview

A graphical and mathematical model of the elements of a system permitting the calculation of system reliability given the reliability of the elements. The model reflects the reliability performance structure including series, parallel, standby and other arrangements of system elements.

Each block in an RBD represents a component or subsystem of the system. The organization and connecting lines represent the reliability structure of the system and may or may not be representative of the system’s functional block diagram. Continue reading

k out of n

k out of n system

The design of a product includes the arrangement of all of the product elements. When considering the reliability of system, the arrangement matters. Many systems are arranged serially. This means that with the failure of any one element, the system will not work. See the article on Series Systems for more details. Continue reading

Exponential Reliability

Down to the last week of preparation for the exam on March 2nd. Good luck to all those signed up for that exam date. Time to focus on preparing your notes, organizing your references and doing a final run though of practice exams. Continue reading

RBD and Design Process

A reliability block diagram (RBD) for a product that has no redundancy or complex use profile, is often very simple. A series system (reliability wise) implies that any one part or element of the product that fails the entire product fails. One might ask if an RBD is even necessary. Continue reading

Series System

During design and development, Reliability Engineers often receive reliability parameters in many forms. The most common reliability parameter is the mean time to failure (MTTF), which can also be specified as the failure rate (this is expressed as a frequency or Conditional Probability Density Function (PDF)) or the number of failures during a given period. Continue reading

Parallel Systems

Speaking reliability-wise, parallel, means any of the elements in parallel structure permit the system to function. This does not mean they are physically parallel (in all cases), as capacitors in parallel provide a specific behavior in the circuit and if one capacitor fails that system might fail.
In this simple drowning there are n components in parallel and any one component is needed for the system to function. Continue reading

Weakest Link

Each piece of gear used in rock climbing has the potential to be the weakest link. Often, based on accident reports, it the human decisions or lack of focus that is the most difficult to improve.

Ropes, anchors, harness, and carabiners and another equipment all has to work in the event of a fall. The design of each piece of equipment is to meet and hopefully exceed any possible load. And, to maintain the needed strength over years of harsh outdoor use. Continue reading