Danger deviation

Do not hesitate to combine some of these tools. For example, when doing a hazard analysis or HAZOP, add a hnman factors analysis (as a subset of the overall hazard analysis) if hnman operators play a significant role. Or, if the HAZOP has identified particularly dangerous deviations of the process resulting from a failure in the system, do an FMEA or fault tree analysis of just that critical subsystan. 

Another danger of an inadequate appreciation of human causes of hazards is that the HAZOP analyst may consider a particular high risk event (identified by a guide word and deviation) to be noncredible, because he or she only takes into accoimt the hardware failures (with an extremely low probability) that could give rise to the event. When human causes are taken into accoimt, the likelihood of the event may actually be quite high. 

The standard deviation, Sj, is the most commonly used measure of dispersion. Theoretically, the parent population from which the n observations are drawn must meet the criteria set down for the normal distribution (see Section 1.2.1) in practice, the requirements are not as stringent, because the standard deviation is a relatively robust statistic. The almost universal implementation of the standard deviation algorithm in calculators and program packages certainly increases the danger of its misapplication, but this is counterbalanced by the observation that the consistent use of a somewhat inappropriate statistic can also lead to the right conclusions. 

Stopping excursions from normal operation conditions before they become hazardous, by correction of process control variables when dangerous situations are detected on-line detection of process deviations associated with trip systems for corrective actions. 

Processes can be divided into those that are intrinsically safe, and those for which the safety has to be engineered in. An intrinsically safe process is one in which safe operation is inherent in the nature of the process a process which causes no danger, or negligible danger, under all foreseeable circumstances (all possible deviations from the design operating conditions). The term inherently safe is often preferred to intrinsically safe, to avoid confusion with the narrower use of the term intrinsically safe as applied to electrical equipment (see Section 9.3.4). 

Clearly, the designer should always select a process that is inherently safe whenever it is practical, and economic, to do so. However, most chemical manufacturing processes are, to a greater or lesser extent, inherently unsafe, and dangerous situations can develop if the process conditions deviate from the design values. 

The correlation coefficients between a 10 year monthly mean time series of volatilisation rates and SST, 1 Om wind speed and pollutant concentration are used to elucidate which of the parameters drives the volatilisation rate changes and causes the deviations from the long term mean. All of the parameters do not vary independently. Since both SST and wind speed influence the volatilisation rate in a nonlinear manner, it is not intuitive whether an increase in wind speed leads to an increase in volatilisation rate. A raise in wind speed that coincides with a decrease of the sea surface temperature can lead to a negative linear correlation coefficient between volatilisation rate and wind speed. For that reason the partial correlation coefficient is calculated in addition to the simple linear correlation coefficients. It explains the relation between a dependent and one or more independent parameters with reduced danger of spurious correlations due to the elimination of the influence of a third or fourth parameter, by holding it fixed. One important feature of the partial correlation coefficient is, that it is equal to the linear correlation coefficient if both variables... 

The combination of empirical and multivariate modeling elements makes chemometrics both very powerful and very dangerous. The power of chemometrics is that it can be used to model systems that are both unknown and complex. Furthermore, these models are not restricted by theoretical constraints - which can be a big advantage if large deviations from theoretical behavior are known to be present in your system. 

Designers and operators of pumps should know that it could be dangerous to operate the machine for example when an outlet valve at the discharge site of the pump is closed. Such a situation must be avoided by a suitable instrumentation and monitoring of that deviation from the safe condition. 

Cocaine, amphetamine, methamphetamine, alcohol, and cannabinoids have already been suspected as aggravating the deadly effects of PMA. As with all drugs, the potency and quality of PMA pills may deviate substantially from one batch to another. Different pills may contain varying amounts of the drug. The clandestine labs that manufacture these illicit drugs are often very dirty, and the pills they generate may contain many dangerous contaminates in addition to PMA. 

For smaller hydro power systems, such a solution is considered to be complex and additionally a danger exists of rapid control valve movement introducing damaging surge pressure waves in the pipelines or instability in the overall control system (Roberts, 2002). A preferable solution to maintain frequency close to its nominal value is the utilisation of load control. For the implementation of this scheme, secondary or even dump controllable loads are switched on and off, according to frequency-deviation measurements. 

Considering calcite equilibrium a pHc of 7.076 results, that is 0.376 pH units above the measured pH value of 6.7. The permitted deviation of 0.2 is exceeded. Since pH-pHc is negative, the water is calcite aggressive, i.e., it can still dissolve calcite and present a danger for pipe corrosion. Undersaturation can also be determined without calculation of the pHc, because within initial solution calculations in the PHREEQC output, calcite already shows a saturation index of -0.63 (= 23% saturation). 

The values from the three-parameter determination agree with the true values well within the 95 percent confidence limits quoted for the former. However, the values from the two-parameter determination deviate from the true values by 12 and 26 times the confidence limits This provides further illustration of the danger of relying on estimated uncertainties when the model may be defective. 

---