Reliability redundancy

Individual philosophy toward reliability, redundancy, and sanity of putting all polishers on a single delivery system. 

The following list summarizes a possible setup of formats for a reliable, redundant chemical structure catalog based on the recommendations above ... 

We can characterize information in many ways. Among attributes that we noted earlier and might use are accuracy, precision, completeness, sufficiency, understandabUity, relevancy, reliability, redundancy, verifiability, consistency, freedom from bias, frequency of use, age, timeliness, and uncertainty. Our concerns with information involve at least five desiderata (Sage 1987) ... 

Separation of Protection and Control Systems. The protection system shall be separated from control systems to the extent that failure of any single control system component or channel, or failure or removal from service of any single protection system component or channel which is common to the control and protection system leaves intact a system satisfying all reliability, redundancy, and independence requirements of the protection system. Interconnection of the protection and control systems shall be limited so as to ensure that safety is not significantly i mpa i red. 

The main criteria used in the design of safety systems were simplicity, reliability, redundancy... 

The main criteria used in the design of safety systems were simplicity, reliability, redundancy and passivity. Special emphasis has been put on minimizing the dependence on active components and operators actions (figure 3). 

Coelho, L.S., An elficient particle swarm approach for mixed-integer programming in reliability-redundancy optimization applications. Reliab Eng Syst Safety, 2009, 94(4), Pages 830-837. 

In order to cope with the design basis accidents (DBA), safety systems are installed which are reliable, redundant and, to a far-reaching extent, diverse and which perform their functions if the outside power supply fails. The efficiency and reliability of these systems is demonstrated in detail in the course of the licensing process and during subsequent operation. The concept of incident control has proven its worth. 

In the US, the staff reviews that each EDG is seismically qualified and is located in a separated seismically qualified room has a reliable, redundant starting air system of adequate capacity. As a minimum, the air starting system should be capable of cranking a cold diesel engine five times without recharging the receivers. 

IU.4.1.5. Highly reliable/redundant initiation of safety systems... 

The CAREM concept greatly enhances accident prevention and mitigation by simplicity, reliability, redundancy and passivity. Nevertheless, in case of the extremely low probability of... 

Defence-in-depth is a basic philosophy for the GTHTR300 as well as for the Light Water Reactors (LWRs). Various layers of defence are used to maintain safety. However, major differences of the safety philosophy between the GTHTR300 and the current LWRs are the following the LWR uses highly reliable, redundant and diverse passive or active safety features. On the other hand, GTHTR300 safety would be maintained mostly due to inherent safety characteristics and potentially safe components. 

It should be noted that, unlike the functional and reliability redundancies, the redundancy for limiting the risk of catastrophic faults does not need to be available at all time. It is only used when the system is in the state of disorder after a catastrophic fault. This can be the basis of a number of different risk mitigation strategies. Some interesting approaches to dealing with this are ... 

System and component reliability, redundancy, and complexity comparisons ability to accommodate any unforeseen casualties or alternate operating modes Component availability and technology development challenges (e.g. high temperature, large diameter, long life gas valves)... 

Amster and Hooper, 1986). Other formulations exist for eomponents in parallel with equal reliability values, as shown in equation 4.69, and for eombinations of series, parallel and redundant eomponents in a system (Smith, 1997). The eomplexity of the equations to find the system reliability further inereases with redundaney of eomponents in the system and the number of parallel paths (Burns, 1994) ... 

Forced Circulation System—Using foreed eireulation in a waste heat reeovery system allows the use of smaller tube sizes with inherent inereased heat transfer eoeffieients. Flow stability eonsiderations must be addressed. The reeireulating pump is a eritieal eomponent from a reliability standpoint and standby (redundant) pumps must be eonsidered. In any event, great eare must go into preparing speeifieations for this pump. 

The objective is to estimate, numerically, the probability that a system composed of many components will fail. The obvious question is, "Why don t you just estimate the failure rate of the system from operating experience " There are three reasons IJ the system may not exist, so new data are not available, 2) the injuries and fatalities from the developmental learning experience are unacceptable - the risk must be known ahead of time, and 3) by designing redundancy, the probability of the system failing can be made acceptably remote in which case system failure data caimot be collected directly. The only practical way uses part failure statistics in a system model to estimate the system s reliability. 

KDC has a cause and effect relationship between as the primary cause leading to secondary failures. Besides its drastic operational effects on redundant systems, the numerical etlects that reduce sy.stem reliability are pronounced Equation 2.4-5 shows that the probability ut failing a redundant. system composed of n components is the component probability raised to the n-th power. If a common clement couples the subsystems. Equation 2.4-5 is not correct and the failure rate is the failure rate of the common element. KDC is very serious because the time from primary failure to secondary failures may be too short to mitigate. The PSA Procedures Guide (NUREG,/CR-2.3(X)) cl.issities this type as "Type 2."... 

Some licensees have a switch to bypass RCIC high steam tunnel temperature trips. Some licensees are evaluating improvements to prevent seal LOCAs from loss of seal cooling which are most important for W plants, but B W licensees identified improvements related to alternate seal flow capability under loss of power conditions. The use of high temperature seals is noted for some W plants. Many PWR IPEs identify AFWS improvements. These include additional backup water supplies such as the firewater system and redundant pump cooling capability. Other reliability... 

Redundant service water supplies to the shutdown cooler for improved shutdown cooling reliability... 

Fleming, K, N cs al., 1975, A Reliability Model for Common Mode Failures In Redundant Safety Systems, Proceedings of the Sixth Annual Pittsburgh Conference on Modeling and Simulation, April. 

The binomial distribution can be used to calculate tlie reliability of a redundant syslein. A redundant system consisting of n identical components is a system tliat fails only if more tlian r components fail. Familiar examples include single-usage equipment such as missile engines, sliort-life batteries, and flash bulbs, which are required to operate for one time period and are not reused. Associate "success with tlie failure of a component. Assume tliat tlie n components are independent witli respect to failure, and tliat tlie reliability of each is 1 - p. Then X, tlie number of failures, has tlie binomial pdf of Eq. (20.5.2) and the reliability of the redundtuit system is... 

For example, consider tlie case of a standby redundancy system consisting of one operating pump and two on standby so that tlie system can survive two failures. Assume tlutt tlie pumps are independent with respect to failure and tliat each lias a probability of failure of 0.1. Thus, n = 3, r = 2, 1 - p = 0.9, and tlie reliability of the system is found from Eq. (20.5.3)... 

In addition to tlie applications cited above, tlie Poisson distribution can be used to obtain tlie reliability of a standby redundancy system, in which one unit is in tlie operating mode and n identical units are in standby mode. Unlike a... 

Tliis is tlie probability if n or fewer failures in the time period specified by t. For example, consider tlie case of a standby redundancy system with one operating unit and one on standby (i.e., a system tliat can survive one failure). If the failure rate is 2 units per year, then tlie 6-nionth reliability of the system is... 

The bulk system has long been seen as a vital element in the maintenance of an economic and reliable supply of electrical energy in North America, and a high degree of redundancy has been incorporated to achieve this objective. The North American Electric Reliability Council (NERC) was formed in 1968, following the November 9-10, 1965, blackout that affected the northeastern United States and Ontario,... 

A further consideration when combining databases from multiple suppliers is how to identify and deal with redundant compounds. Here, some method of mapping multiple supplier information onto a single compound is needed for efficiency. Generally, all information can be mapped, although some consideration of cost and supplier reliability may allow a hierarchy of supplier information to be applied. 

An inherently safe plant1112 relies on chemistry and physics to prevent accidents rather than on control systems, interlocks, redundancy, and special operating procedures to prevent accidents. Inherently safer plants are tolerant of errors and are often the most cost effective. A process that does not require complex safety interlocks and elaborate procedures is simpler, easier to operate, and more reliable. Smaller equipment, operated at less severe temperatures and pressures, has lower capital and operating costs. 

Systems are designed to function normally even when a single instrument or control function fails. This is achieved with redundant controls, including two or more measurements, processing paths, and actuators that ensure that the system operates safely and reliably. The degree of redundancy depends on the hazards of the process and on the potential for economic losses. An example of a redundant temperature measurement is an additional temperature probe. An example of a redundant temperature control loop is an additional temperature probe, controller, and actuator (for example, cooling water control valve). 

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