- •14 4.5 Reliability test requirements
- •2 Reliability engineering for complex systems requires a different, more elaborated systems approach than reliability for non-complex systems
- •9 4 Reliability program plan
- •11 4.2 Reliability prediction
- •9 4 Reliability program plan
- •52 Main articles: reliability theory, failure rate.
- •106 The parts stress modelling approach is an empirical method for prediction based on counting the number and type of components of the system, and the stress they undergo during operation.
- •18 7 Accelerated testing
- •39 The probability that a functional unit will perform its required function for a specified interval under stated conditions.
- •12 4.3 System reliability parameters
- •2 Reliability engineering for complex systems requires a different, more elaborated systems approach than reliability for non-complex systems
- •82 Reliability predictions:
- •20 9 Reliability operational assessment
- •21 10 Reliability organizations
- •7 2 Reliability theory
- •36 The capacity of a device or system to perform as designed;
- •20 9 Reliability operational assessment
- •34 Reliability may be defined in several ways:
- •57 Where is the failure probability density function and t is the length of the period of time (which is assumed to start from time zero).
- •58 Reliability engineering is concerned with four key elements of this definition:
- •2 Reliability engineering for complex systems requires a different, more elaborated systems approach than reliability for non-complex systems
- •48 Automotive engineers have reliability requirements for the automobiles (and components) which they design
- •49 Electronics engineers must design and test their products for reliability requirements.
- •127 Failures from occurring. Rcm (Reliability Centered Maintenance) programs can be used for this.
- •96 Serial System: Any assembly of units for which the failure of any single unit will cause a failure of the system or overall mission.
- •45 Many types of engineering employ reliability engineers and use the tools and methodology of reliability engineering. For example:
- •33 A reliability block diagram
- •58 Reliability engineering is concerned with four key elements of this definition:
- •40 The ability of something to "fail well" (fail without catastrophic consequences)
- •23 12 Reliability engineering education
- •148 Human error analysis
- •39 The probability that a functional unit will perform its required function for a specified interval under stated conditions.
20 9 Reliability operational assessment
64 Reliability engineering differs from safety engineering with respect to the kind of hazards that are considered. Reliability engineering is in the end only concerned with cost. It relates to hazards that could transform into a particular level of loss of revenue for the company or the customer. These can be cost due to loss of production due to system unavailability, unexpected high or low demands for spares, repair costs, man hours, (multiple) re-designs, interruptions on normal production (e.g. due to high repair times or due to unexpected demands for non-stocked spares) and many other indirect costs. Safety engineering, on the other hand, is more specific and regulated. The related reliability Requirements are sometimes extremely high. It deals with unwanted dangerous events (for life and environment) in the same sense as reliability engineering, but does normally not directly look at cost and is not concerned with repair actions after failure. Another difference is the level of impact of failures on society and the control of governments. Safety engineering is often strictly controlled by governments (e.g. Nuclear, Aerospace, Defense, Rail and Oil industries). Furthermore, safety engineering and reliability engineering often have contradicting requirements.For example, in train control systems it is common practice to use many fail-safe devices and to lower trip settings as needed. This will unfortunately lower the reliability. Reliability can be increased here by using redundant systems, this does however lower the safety levels. The only way to increase both reliability and safety on a systems level is by using fault tolerant systems. In this case the "operational"
67 Many tasks, methods, and tools can be used to achieve reliability. Every system requires a different level of reliability. A commercial airliner must operate under a wide range of conditions. The consequences of failure are grave, but there is a correspondingly higher budget. A pencil sharpener may be more reliable than an airliner, but has a much different set of operational conditions, insignificant consequences of failure, and a much lower budget.
103 Reliability modelling is the process of predicting or understanding the reliability of a component or system prior to its implementation. Two types of analysis that are often used to model a system reliability behavior are Fault Tree Analysis and Reliability Block diagrams. On component level the same analysis can be used together with others. The input for the models can come from many sources, e.g.: Testing, Earlier operational experience field data or Data Handbooks from the same or mixed industries can be used. In all cases, the data must be used with great caution as predictions are only valid in case the same product in the same context is used. Often predictions are only made to compare alternatives.
149 Operational Hazard analysis
156 Reliability testing may be performed at several levels. Complex systems may be tested at component, circuit board, unit, assembly, subsystem and system levels. (The test level nomenclature varies among applications.) For example, performing environmental stress screening tests at lower levels, such as piece parts or small assemblies, catches problems before they cause failures at higher levels. Testing proceeds during each level of integration through full-up system testing, developmental testing, and operational testing, thereby reducing program risk. System reliability is calculated at each test level. Reliability growth techniques and failure reporting, analysis and corrective active systems (FRACAS) are often employed to improve reliability as testing progresses. The drawbacks to such extensive testing are time and expense. Customers may choose to accept more risk by eliminating some or all lower levels of testing.
185 Reliability operational assessment
187 One of the most common methods to apply a reliability operational assessment are Failure Reporting, Analysis and Corrective Action Systems (FRACAS). This systematic approach develops a reliability, safety and logistics assessment based on Failure
organizations