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Design of the speed governors for hydraulic turbines by Amesim
Published in Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi, Simulation of Fluid Power Systems with Simcenter Amesim, 2018
Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi
The main redundant designs used in the field of hydraulic and pneumatic systems can be split into active redundancy and passive redundancy. In the case of passive redundancy, only one system is working at a given time. When the main system malfunctions, the backup system takes over. The malfunctions are detected by constant supervision of the active system. For this type of redundancy, it is important that the backup system has a greater operational safety than the main system and that the supervision system does not malfunction. These types of systems have several disadvantages, such as the time needed to activate the backup system, the backup system needs to be as large as the main system to accomplish the operating requirements (force, torque, etc.) are met. Active redundancy has two or more systems operating at the same time. The tasks are split between them, the output of the actuators being a sum of all forces. When a malfunction occurs, the damaged system is disconnected and the operation is taken over by the functional system. An example of a passively redundant control system will be built for a simple electrohydraulic servomechanism (Figure 9.1.36). The system’s response at a step input can be seen in Figure 9.1.37.
Designing for Reliability
Published in Armand A. Lakner, Ronald T. Anderson, Reliability Engineering for Nuclear and Other High Technology Systems, 2017
The functional reliability of the equipment can be greatly increased by redundant design. There are two major classes of redundancy: active redundancy, in which redundant elements are always a functioning part of the equipment, and standby redundancy, where an external element must make a decision to switch to another element that has not been active in the system. Formulae for estimating the reliability of equipment with redundant elements are given in Chapter 2. It should be noted that plant safety is ensured through use of reliable equipment and through application of additional backup systems and equipment as well as through the employment of diversity and alternate modes of operation as established by a plant safety analysis.
Hardware Design
Published in Richard C. Fries, Handbook of Medical Device Design, 2019
Active redundancy occurs when two or more components are placed in parallel, with all components being operational. Satisfactory operation occurs if at least one of the components functions. If one component fails, the remaining parts will function to sustain the operation. Active redundancy is important in improving the reliability of a device. Placing components redundantly increases the MTBF of the circuit, thus improving reliability. Consider the following example.
Hidden overdesign in building services: insights from two UK hospital case studies
Published in Journal of Engineering Design, 2023
Redundancy definitions fundamentally fall into two categories: duplication, where an additional system of the same specification is provided (often referred to N + 1 or ‘like for like’) and substitution, where a different solution principle is used to carry out the same function (Chen and Crilly 2014). The architects of a system can pursue different strategies during normal operation. Active redundancy is load that is shared across multiple potentially identical components during normal operation, but other components can step up the load if a component fails. Whereas passive redundancy leaves the components that are not required inactive (Pahl and Beitz 1996). Passive redundancy can further be broken down into cold redundancy, where is it not absolutely time critical for a component to come online, warm redundancy where the system can tolerate a short outage and hot redundancy, where the system has to function under all circumstances (Nguyen, Mhenni, and Choley 2016). Partial redundancy is provided if all components usually work, but the system can withstand individual components that do not work (Thompson 1999).
An overview of self-engineering systems
Published in Journal of Engineering Design, 2021
Other categories of redundancy relate to how the components are used before they are required for a repair or reconfiguration (Chen and Crilly 2014). Active redundancy – Different material or components share a set function; if one (or more) is lost, the others maintain the function.Partial active redundancy – Various system functions are maintained by all components or materials and can be maintained even after some components are damaged.Passive redundancy – Spare components and material are inactive and activated to replace broken ones.