Errors operator

Later than 2. Operator error 1. Temperature rises, possible 1. Interlock between cooling flow and JEH 1/93... 

The analytical uncertainty should be reduced to one-third or less of sampling uncertainty (16). Poor results obtained because of reagent contamination, operator errors ia procedure or data handling, biased methods, and so on, can be controlled by proper use of blanks, standards, and reference samples. 

By assuming such responsibilities, the control system greatly reduces the incidences where operator error results in off-specification batches. Such a reduc tion in error is essential to implement just-in-time production practices, where each batch of product is manufactured at the last possible moment. When a batch (or batches) are made todav for shipment by overnight truck, there is insufficient time for producing another batch to make up for an off-specification batch. 

Common usage. Steam tracing has been around for many years and many operators are famihar with the system. Because of this familiarity, failures due to operator error are not very common. 

Systematic Operating Errors Fifth, systematic operating errors may be unknown at the time of measurements. Wriile not intended as part of daily operations, leaky or open valves frequently result in bypasses, leaks, and alternative feeds that will add hidden bias. Consequently, constraints assumed to hold and used to reconcile the data, identify systematic errors, estimate parameters, and build models are in error. The constraint bias propagates to the resultant models. 

Overfill drum due Calibrate weighing devices and maintain equip-to operator error ment in good working order or valve failure,. metering pumps can lead to opera- tor exposure, slip- fill operation with weighing device pery floors, spread of flammable liquids. CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29... 

Overfill by plugging, blinding cloth, failure to start underflow pump, loss of vacuum or by operator error. 

To be able to systematically identify opportunities for reducing human error, it is useful to ask the question, What is human error One definition is that human error is an inappropriate or undesirable human decision or behavior that reduces, or has the potential for reducing safety or system performance (Rasmusssen 1979). There is a tendency to view errors as operator errors. However, the error may result from inadequate management, design, or maintenance of the system. This broader view which encompasses the whole system can help provide opportunities for instituting measures to reduce the likelihood of errors. 

Listed below are operator related safety issues that are more prevelant in batch operations. Keep in mind, however, that human error consists of more facets than operator error alone. 

Use of portable equipment and temporary connections for processing. There is a possibility of operator error in making connections. This may lead to hazardous release, ignition or explosion (see also Chapter 4). 

There are a variety of ways to express absolute QRA results. Absolute frequency results are estimates of the statistical likelihood of an accident occurring. Table 3 contains examples of typical statements of absolute frequency estimates. These estimates for complex system failures are usually synthesized using basic equipment failure and operator error data. Depending upon the availability, specificity, and quality of failure data, the estimates may have considerable statistical uncertainty (e.g., factors of 10 or more because of uncertainties in the input data alone). When reporting single-point estimates or best estimates of the expected frequency of rare events (i.e., events not expected to occur within the operating life of a plant), analysts sometimes provide a measure of the sensitivity of the results arising from data uncertainties. 

Variations in a produet s material properties, serviee loads, environment and use typieally lead to random failures over the most protraeted period of the produet s expeeted life-eyele. During the eonditions of use, environmental and serviee variations give rise to temporary overloads or transients eausing failures, although some failures are also eaused by human related events sueh as installation and operation errors rather than by any intrinsie property of the produet s eomponents (Klit et al., 1993). Variability, therefore, is also the souree of unreliability in a produet (Carter, 1997). However, it is evident that if produet reliability is determined during the design proeess, subsequent manufaeturing, assembly and delivery of the system will eertainly not improve upon this inherent reliability level (Kapur and Lamberson, 1977). 

Pure preventive maintenanee alone eannot eliminate breakdowns. Breakdowns oeeur due to many faetors sueh as, design and or manufaeturing errors, operational errors, and wearing out of various eomponents. Thus, ehanging out eomponents at fixed intervals does not solve the problems and in some eases adds to the problem. A study at a major nuelear power station indieated that nearly 35% of the failures oeeurred within a month of a major turnaround. Figure 21-2 shows the life eharaeteristies of a major pieee of turbomaehinery. 

Cause Design Manufacturing Errors Operational Errors Wear Out... 

Excessive feed preheat. Flooding of rectification section packed bed. Operational error. 

If a tower does become flooded in the bottom section, a common operator error is to try to pump the level out too quickly. This can easily damage trays by imposing a downward acting differential pressure produced by a large weight of liquid on top of the tray and a vapor space immediately below the tray. To eliminate the flooding, it is better to lower feed rate and heat to the reboiler. It is important to be patient and avoid sudden changes. 

API 2003 and BS 5958. This took into account the possibility that credit might be taken for larger upstream pipe as described in BS 5958 and that operational errors such as partial dip pipe insertion might occur. 

Simplify Design facilities which eliminate unnecessary complexity and make operating errors less likely, and which are forgiving of errors which are made (also called Error Tolerance). 

Can equipment be designed such that it is difficult or impossible to create a potential hazardous situation due to an operating error (for example, by opening an improper combination of valves) ... 

Human operator errors are not usually examined in a FMEA, but the effects of human error are indicated by the equipment failure mode. FMEAs rarely investigate damage or injury that could arise if the system or process operated successfully. Because FMEAs focus on single event failures, they are not efficient for identifying an exhaustive list of combinations of equipment failures iliat iead to accidents. 

The confusion matrix (NSAC-60) is a method that identifies potential operator errors lemming from incorrect diagnosis of an event. It can be used to identify the potential for an operator to conclude that a small LOCA has occurred, when it is actually a steam line break. This provides a method for identifying a wrong operator response to an off-normal plant condition. It is particularly useful in Step 5 of the. SHARP procedures, Documentation requirements are presented in Table 4.5-2. 

Pressure relief valves failed to reclose, and Operator error in failing to diagnose the accident and in tripping the automatic ECCS operation. 

Operational Error Design Error Process Upset Mechanical Failure Unknown Natural Hazard Sabolage/Arson... 

The most frequent loss mechanism (43%) was mechanical failure of equipment which was second in terms of average loss at 72,100,000 (Figure 7.1-4). Operational error was the second most frequent cause of loss (21%), but it had the highest average loss ( 87,400,000). 

Operator error probabilities were estimated using NUREG/CR-4910 normalized to errors determined in the internal events analysis. This allowed for varying number of personnel, amount of time available, and stress level. When more pessimistic values were substituted for best estimate values, the calculated core melt frequency increased by a factor of at least three. 

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