16.422 Human Supervisory Control Nuclear and Process Control Plants Massachusetts Institute of Technology
16.422 Human Supervisory Control Nuclear and Process Control Plants
Process Control plants 16.422 Continuous or batch processing Examples: Electricity generation(nuclear power plants), refineries, steel production, paper mills, pasteurization of milk Characterized by Large scale, both physically and conceptually Complex High risk High automation Remote vS direct manipulation of plant equipment
Process Control Plants 16.422 • Continuous or batch processing • Examples: Electricity generation (nuclear power plants), refineries, steel production, paper mills, pasteurization of milk • Characterized by: – Large scale, both physically and conceptually – Complex – High risk – High automation • Remote vs. direct manipulation of plant equipment
Three mile island 16.422 · March28th,1979 Main feedwater pump failure, caused reactor to shut down Relief valve opened to reduce pressure but became stuck in the open position No indication to controllers Valve failure led to a loss of reactant coolant water No instrument showed the coolant level in the reactor Operators thought relief valve closed water level too high High stress Overrode emergency relief pump
16.422 Three Mile Island • March 28th, 1979 • Main feedwater pump failure, caused reactor to shut down • Relief valve opened to reduce pressure but became stuck in the open position – No indication to controllers – Valve failure led to a loss of reactant coolant water • No instrument showed the coolant level in the reactor • Operators thought relief valve closed & water level too high – High stress – Overrode emergency relief pump
Three Mile island 16.422 Automation worked correctly Confirmation bias: people seek out information to confirm a prior belief and discount information that does not support this belief At TMl, operators selectively filtered out data from other gauges to support their hypothesis that coolant level was too high
Three Mile Island 16.422 • Automation worked correctly • Confirmation bias: people seek out information to confirm a prior belief and discount information that does not support this belief – At TMI, operators selectively filtered out data from other gauges to support their hypothesis that coolant level was too high
Process control human factors Challenges 16.422 Control room design Increasing automation requires cognitive support as opposed to manual control support Human-machine interface design · Team decision making Standardized procedures vs innovation Trust confidence
Process Control Human Factors Challenges 16.422 • Control room design • Increasing automation requires cognitive support as opposed to manual control support • Human-machine interface design • Team decision making • Standardized procedures vs. innovation • Trust & confidence
Supervisory process Control Tasks 16.422 Monitor process Detect disturbances faults abnormalities Counter disturbances faults abnormalities Operating procedures must be followed Communications a log must be kept Other team members(shift changes Emergency procedures Training and retraining
Supervisory Process Control Tasks 16.422 • Monitor process • Detect disturbances, faults, & abnormalities • Counter disturbances, faults, & abnormalities • Operating procedures must be followed • Communications – A log must be kept – Other team members (shift changes) • Emergency procedures • Training and retraining
Cognitive Demands When Monitoring process Control Plants 16.422 g ance Continuous vs. time share Active vs passive monitoring Memory Selective attention Visual attention/perception System complexity System reliabil Critical vS. non-critical components
16.422 Cognitive Demands When Monitoring Process Control Plants • Vigilance – Continuous vs. time share – Active vs. passive monitoring • Memory • Selective attention • Visual attention/perception • System complexity • System reliability – Critical vs. non-critical components
Cognitive demands. cont 16.422 Display and control design Lack of referent values Lack of emergent features Lack of integrated information alarm system design Nuisance alarms Cycling around limits · Desensitization · Automation design ack of appropriate feeabac Direct vs indirect cues
Cognitive Demands, cont. 16.422 • Display and control design – Lack of referent values – Lack of emergent features – Lack of integrated information • Alarm system design – Nuisance alarms – Cycling around limits • Desensitization • Automation design – Lack of appropriate feedback – Direct vs. indirect cues
Coping Strategies 16.42 Increase desired information salience and reduce background noise Clearing and disabling alarms Cross checking with other reactors Create new information Operators manipulated set points for earlier alarms Offload cognitive processing onto external alas eaving doors open sticky notes Deviations from"approved? procedures
16.422 Coping Strategies • Increase desired information salience and reduce background noise – Clearing and disabling alarms – Cross checking with other reactors • Create new information – Operators manipulated set points for earlier alarms • Offload cognitive processing onto external aids – Leaving doors open & sticky notes • Deviations from “approved” procedures
Advanced displays in Process control 16.42 Classical displays(bar graphs, meters annunciators)are being replaced with computerized displays Keyhole effect Temporal considerations Integration of information Flexible adaptable displays Local vs global problems Configural Ecological displays
16.422 Advanced Displays in Process Control • Classical displays (bar graphs, meters, annunciators) are being replaced with computerized displays – Keyhole effect – Temporal considerations – Integration of information • Flexible & adaptable displays – Local vs. global problems • Configural & Ecological displays