Double failure

Beyer WEP, Diepersloot RJA, Masurel N, Simoons ML, Weimar W. Double failure of influenza vaccination in a heart transplant patient. Transplantation (1987) 43, 319. 

Many hazard analysis and risk assessment techniques have been developed. These are just a few of the methodologies mentioned in the literature preliminary hazard analysis gross hazard analysis hazard criticality ranking catastrophe analysis change analysis energy flow/barrier analysis energy transfer analysis event tree analysis human factors review the hazard totem pole and double failure analysis. There are many other hazard analysis systems. 

The rationale for these cases follows. In (23) the hidden failure exists at time sa So the system failure is triggered at sa- The next repair is due at since at the beginning of the next flight the double failure must not exist. If, as in (23.1), there is no maintenance task for the H-failure at "ij", then the Go-failure is removed. In the opposite case (23.2) the Go-failure is tolerated. However, there is possibly a H-failure before the end of the tolerance time. In (24) the hidden failure does not exist at sa- So, the Go-failure will be removed at the latest at Sr. In (24.1), there is no H-failure inbetween. However, if there is a H-failure, hence the system fails at 2m — 1, a failure (Go or H) has to be removed at "M2m-i If there is, (24.2), no H-maintenance task, then the Go-failure is removed. Else, (24.3), the Go-failure is further tolerated. As above. 

The safe hfe principle requires detection of aU critical failures and an adequate safety reaction. During this time, the system must still be safe enough. This requires monitoring of critical components Note that redimdancy itself is not enough since dormant failiues of these components must be prevented. This must be combined with appropriate action to prevent the occurrence of double failure. For this reason, automatic safety braking on detection of critical faQiues is implemented. By this approach the accinnulation of faults is prevented, since this would be crucial for safe-hfe systems. 

TMR). If in place of three there are N numbers of such selection, then voting is N-modular redundancy (NMR). In this case of TMR, in the case of a double failure (item or voting circuit) output will fail silent fault , whereas in the case of a single fault (in each item or voting circuit) it is a single fault tolerant Byzantine fault. 

This method is based on the empirical formula for the research of electronic products in USA. Namely the temperature raises every 10 C, the double failure rate rises ... 

Node EVC B, ProciVCX NE.C P.P 60.0,150.0 Double failure (Node B stops, then processor C inccrrect)... 

Dependent double failure Inner tube failure caused by outer tube failure or outer tube failure caused by inner tube failure. 

Independent double failures Inner and outer tube failure coincidently happen at the same tube. 

Double failure in a Cooling by DRAGS with low sodium level in case of... 

Some Member States use explicit reliability requirements. In other Member States, reliability is only one aspect of demonstration of the performance required of safety systems and equipment. Various national practices have set goals for the performance of the protection system over and above the single failure criterion. This additional reliability is sometimes achieved by using double failure protection in parts of the protection system and/or by using equipment with a wider design margin. 

A single failure may overload the remaining channels, thereby increasing the probability of their failure. For example. In a two-channel system, each channel with a failure rate of 1 in 1000 hrs, the probability of any one of the channels failing is 3 x 10 . So in a period of a million hrs, there will be 2000 failures. The probability of two chaimels failing is (10 ), i.e., one double failure in a million hrs. However, if the failure of the first chaimel will cause a ten-fold increase in the probability of the second channel also failing, then the probability of total failure is (1/1000) X (1/100), i.e., ten such double failures in a million hrs. 

For example, double failure may allow system to operate, but possibly at a reduced capacity). 

Consider the probability of a double engine failure on the Tristar aircraft (which has three engines). The dependence diagram (see Chapter 6) for this double failure condition could be any of the following ... 

Assume a flight of T duration in a twin-engine aircraft and each engine has a probability of p per hour of failing. The probability of a double failure is thus P = p T. After a first engine failure, the pilots may have to decide between the... 

Average and one standard deviation, [2] Double failure, [5] Mixed-mode failure. 

Table 7-8 Impact of Isolation Valve Double Failure Mode on System Reliability.39...

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