Mean downtime

Suppose that stations can fail only when they are working on a part. Let T" be the mean number of cycles station i operates between failures, te the mean downtime of station /, and t be the average cycle time when the line is running and x° = DJ TiT). Then the line consisting just of station / would have efficiency... 

Failure Rate, Failure Rate, Probability of Mean Downtime... 

One difficulty with this type of model is that it is difficult to provide a probability value for an absolute repair time. For example, the Mean Downtime (MDT) for P-lOlB is 3 hours this is the time it takes to repair it when it fails. It may be that this time is an absolute minimum (say due to the time it takes to isolate the pump, drain it down, repair the failure, and bring the pump back into service). Hence a simple probability value cannot truly represent this downtime. 

The true value of 0 is interpreted as the mean downtime when considering an infinite (very large) number of similar tests. The data used in the analysis should be sampled from this population. The question is to what extent this is the case when looking at the assumptions of the uncertainty factors defined above. 

The probability of a transition from a state to another is determined by the failure- or the repair rate, respectively. Particular attention has to be paid to faults of the system due to common-cause failures. As for these failures the system behaves like a 1001-system the mean downtime is not Ti/3 but, as in that case Ti/2. That means one has to differentiate the state of the system where both components are faulty due to a common-cause failure and the state where both are faulty due to two independent failures. 

Mean downtime (given that spare parts are available)... 

PFDavg is derived from the ratio of MDT(T)/T where MDT(T) stands for the mean downtime over a time interval of 0 —T. So, mean downtime of the system is the sum of mean downtime of each bigger block (shown in dotted hatches). 

This is true as long as they are not parallel. In the case of a parallel combination both need to fail. Therefore if mean downtime within the block is (say) 1, 2,3 or F, E, one needs the help of the following equation as an example ... 

Basic Type Failure Mean Downtime/ Constant ... 

A. = failure rate of /th component of a gate Pi = repair rate of ith component of a gate Pi = Steady sate failure probability of a SB AI = Steady sate availability of a SB = SSA of AND OR gate AjvD oR = mean uptime of AND OR gates ANir oR - mean downtime of AND OR gates ano Xor = failure rate of AND OR gates V andN or - repair rate of AND OR gates... 

Pipe-hne and marine installations are frequently arranged so that the engine drives all its auxiharies from the crankshaft by means of chains and V belts. But process-plant practice is to have all the auxiliaries independently driven, using standby pumps to minimize engine downtime. 

The system reliability not only means minimum downtime, but also implies a compliance with the quality of the curing process, and it is the manufacturer s responsibility to design it to meet these criteria. ... 

Although many pressure relief devices are called SRVs, not every SRV has the same characteristics or operational precision. Only the choice of the correct pressure safety device for the right application will assure the safety of the system and allow the user to maximize process output and minimize downtime for maintenance purposes. Making the correct choice also means avoiding interference between the process instrumentation set points in the control loop and the pressure relief device limits selected. These SRV operational limits can vary greatly even when all are complying with the codes. 

Safety clutches usually consist of two parts the actual safety clutch and the elastic part, both of which soften vibrations and shocks and equalize any misalignment between motor and gearbox. Essentially, a distinction is made between slip clutches and mechanically disengaging clutches. Despite their higher cost, pneumatic slip clutches are normally used on larger extruders, because they are easy to handle, which means shorter downtimes in case of overload. 

According to an issne of LC-GC [8], combining CEC with detection techniqnes snch as MS, MS-MS and in-dnctively conpled plasma (ICP)-MS are easier to accomplish, as the flow rates are at nanoliter per minnte levels. Analysts mnst add makenp solvent after the capillary separation for certain ionization methods, and, because it is added later, users can select solvents that are more compatible with the detection techniqne. CEC mobile phases have a high organic solvent content that is more amenable to MS. Also, the low CEC flow rates means less maintenance and downtime for MS sonrce cleaning. 

Reliability refers to the stability of the PACS - meaning the downtime of the system should be nil. If a PACS falters in its operation and encounters frequent failures, it will seriously disrupt the healthcare operation, leading to adverse financial loss. The software should be well written and user-friendly to avoid unnecessary failures of the system. 

Success means improved safety, less downtime, better profitability and greater job security ... 

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