Operator response, importance

Operators typically have long cycle measurements upon which they focus. These may be part of morning reports giving production rates, compositions, yields, and so on. They may also have some recorded measurements that they examine once per shift. Analysts should understand the importance that the operators place on these measurements and the operators responses to them. 

To be effective, the inventory must be isolated quickly to prevent its total contents from being released. Since total release may occur within a few minutes, rapid response and operation is important. 

In addition to the initial evaluation of the credited operator action, a program should be established to ensure that all assumptions about the reliability of the operator response are maintained and improved. This would include, but is not necessarily limited to initial training, refresher training, procedures engineered to decrease the likelihood of human error, important human factors that have been identified. 

The critical alarm management system is very important to operator action. Alarm load, nuisance alarms, and alarm priorities have tremendous effect on an operator s corrective action. For an operator response to be considered an IPL, it needs to meet the following requirements ... 

Timing It is also important to define a minimum operator response time, which is the minimum amount of time that must be provided to the operator for him or her to respond to any alarm in the system. 

In BPCS, operator actions in response to process conditions are not part of a safety system (see lEC 61511 -1 2003 Clause 9.4.2) if risk reduction is less than 10. It is needless to say that BPCS should be designed as per ISA standard for alarm systems. Also the design of a BPCS operator interface should incorporate human factors engineering principles to ensure adequate response of the operator to displays and alarms. It is extremely important that operator response during both normal and abnormal conditions in the facility should not unduly violate process safety limits and norms and put the facility in an unsafe or undesirable mode or condition. 

A sensitivity analysis was performed assuming the operator actions claimed in the PRA are achieved. The resulting core damage frequency indicates that human error is not risk important at the level of plant risk obtained by the base case there is no significant benefit to be gained by improving operator response beyond the assumptions made in the PRA. 

Each alarm should have two important characteristics it should result from an abnormal situation and require a specific operator response. 

There are important figures of merit (5) that describe the performance of a photodetector. These are responsivity, noise, noise equivalent power, detectivity, and response time (2,6). However, there are several related parameters of measurement, eg, temperature of operation, bias power, spectral response, background photon flux, noise spectra, impedance, and linearity. Operational concerns include detector-element size, uniformity of response, array density, reflabiUty, cooling time, radiation tolerance, vibration and shock resistance, shelf life, availabiUty of arrays, and cost. 

One topic of discussion is the measurements to which the operators pay the most attention (their foci). Of the myriad of measurements, there is a limited set that they find most important. These are the measurements that they use to make the short-cycle decisions. The important points to glean are the reasons they focus on these, the values and trends that they expect, and their responses to the deviations from these. 

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