HUMAN RELIABILITY ANALYSIS - EPSC · Web viewCode Description Probability value OA(APR-PC) Operator...
Transcript of HUMAN RELIABILITY ANALYSIS - EPSC · Web viewCode Description Probability value OA(APR-PC) Operator...
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Best Practice Guide
Contemporary state of the scientific knowledge about human factors and labour safety in Slovakia
This guide was prepared by
Ludovit Jelemensky
Department of Chemical and Biochemical Engineering
STU Bratislava
Slovakia
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PRISM – the human factors network
for the process industries
Objective“the improvement of safety in the European process industries through raising awareness of, and sharing experience in, the application of human factors approaches and stimulate their development and improvement to address industry-relevant problems in batch and continuous process industries.”
The PRISM Thematic Network was established in 2001 with financial support from the European Union, DG Research, with the aim of creating an extensive forum within which industry, universities, research centres and practitioners could collaborate to improve the flow of fundamental knowledge and practical experience in human factors and identify areas for improvement by collaborative effort.
All of the deliverables of the Network have been tailored to provide practical guidance on good human factors practices as an aid for the process industries.
StructureThe work of the Network was split into 4 Focus Groups:WP 1 Cultural and organisational factorsWP 2 Optimising human performanceWP 3 Human factors in high demand situationsWP 4 Human factors as part of the engineering design process
The Focus Groups have produced a number of reports and guides as well as leading a series of seminars aimed at facilitating knowledge interchange between Network members; evaluating current experiences in the application of human factors; identifying where new or improved tools or guidance are needed by the process industries, with
particular emphasis on the needs of SMEs, and publish such guidance; and
Each Focus Group was led by a Co-ordinating Partner who co-ordinated the activities, fostered links to end-users, carried out specific tasks and ensured completion of agreed deliverables. Co-ordinating Partners worked closely with an End-user representative who acted in an advisory capacity. All End-user advisors were drawn from EPSC membership and were representatives of manufacturing process industries. This structure has helped to ensure that the activities of the Network were focused on the needs of the process industries.
More information can be obtained from the PRISM website www.prism-network.org
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Legal framework
The directive of the EU Council 89/391/EEC about measures aimed at increasing safety and
health protection of workforces at their workplace attempt the employers to identify and assess
risks threatening the safety and health of employees, and determine and carry out necessary
measures. Furthermore, in planning risk prevention the influence of technique, labor
organization, working conditions, social relations and the environment on the workplace should
be taken into account. A similar approach has the Slovak legislature incorporated in the law of
the National Council of the SR No.330/1996 Collection of Laws concerning the Labor Safety and
Health Protection.
Currently the implementation of legal measures in injuries prevention has still been
oriented on technical and technological areas, and/or labor organization rather than on the
understanding of human factors. In contradiction with calculable engineering quantities in
designing production plants the requirements concerning human behavior and activities are given
in such way that they cover the existing risks regardless to the fact whether these demands can be
fulfilled or not. Just the human error of the employees and/or the failure of human factors are the
most common cause of labor injuries according to statistics. In comparison with direct causal
relations between the cause and consequence, which appear in the majority of cases of technical
character, in the investigation and study of human factors simple causal relations cannot be
applied.
Reliability of the operator’s performance
The reliability of a facility can be defined, in accordance with J. Stikar, J. Hoskovec and M.
Stríženec (1982), as an ability to maintain its functional properties within the given range of
deviations from the indicators of quality at particular operation conditions (work environments,
service, feeding) in the lifetime of the equipment and within the range of operation faults not
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exceeding an acceptable limit. Thus, the reliability is a property to fulfill the required tasks within
the given period at given working conditions. The reliability of an arbitrary system corresponds
to the reliability of its weakest part. In a complex system human being-machine-work
environments, just the human being appears to be the weakest, the least known and controlled
element.
The development of science and technique changes the relation between physical and
mental work, the muscle work is reduced in favor of mental processes (perception, attention,
memory, thinking, decision). The responsibility of the employee is being increased, whereby
emotional stress due to anticipation of possible consequences of own failure is created, because
human error in operator’s activity can trigger serious consequences. The reliability of operator’s
performance, the capability to resist hindrances, safety of operator’s performance and/or the
possibility of his failure is an integral part of the reliability of the whole system and thus, also an
integral part of risk prevention. This is the reason, why it is necessary to minimize the percentage
of failures of the human factor, upon which the same requirements must be laid than on technical
facilities.
Mental workload of the employee
High requirements on labor, process tasks, conditions at which they are performed on the one
hand, and the properties, capabilities and possibilities of the employee on the other hand, can be
in a disharmony, and thus impose an undesirable mental workload on the individual. Usually, the
factors causing undesirable workload vary within a range of average values. In this case one can
speak about a light or medium workload. The psychical workload is high when the factors
causing it are so intensive that situations occur, which threaten the human being or cause
abnormal, erroneous, and thus unreliable responds. A hard psychical workload in the operation
process appears only seldom, however, one cannot exclude it. Here we must emphasize that also
permanent or long-term action of undesirable - though not hard – workload is reflected in the
operator’s performance and its health state.
Consequences of workload
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1. In the sphere of living out a situation: all psychical states with different negative
emotional levels, e. g. fear, anxiety, threat;
2. In the sphere of motory manifestation: increased muscular tension, motory unrest,
mimics, secondary disorders of speech, disorders of motion stereotypes, etc.;
3. In the sphere of cognitive functions: on a lower level, the perception is being changed
(this situation is manifested by inattention, inaccuracy) and on higher level disorders in
ordering, thinking and reduced social adaptation;
4. In the sphere of physiological functions: changes of pulse frequency, blood pressure,
breathing frequency, etc.
From the above-motioned follows that consequences of undesirable workload can highly
negatively influence the human being activities, disintegrate the behavioral tendencies, negatively
affect safety and reliability of operator’s performance.
Consequences of a long-term excessive workload can be manifested at once: by employee ´s
failure in a certain situation, which need not be extraordinary. Then, incidents or accidents and/or
injury are related to the “human factor”, whereby rarely the real cause of human error is found.
More often, the consequences of excessive mental workload are manifested by bad mental state
of individuals, even by mental diseases. In the last years the health statistics have shown that
mental diseases (neuroses, depressions, anxiety, chronic fatigue, etc.) belong to the top ten
diseases, which are the reason of partial or total loss of jobs of human beings in their productive
age.
Also, psychosomatic gastrointestinal and cardiovascular diseases can be induced by a psychic
agent.
Primary workload
The primary workload is caused by own working activities. Many work places are highly
demanding and cannot be run without selection of employees by the assessment of their psychical
capability in relation to the demands upon work. We must take into account individual
characteristics of the employee, developing factors (most often connected with the age) and
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transition variable factors. Judgment of the mental capability and identification of inner
determinants of erroneous, unreliable performance with regard to the demands given by operation
tasks requires the presence and intervention of a highly qualified specialist from the area of
psychological diagnosis.
Secondary workload
In contradiction with primary workload caused by own working activities, outer determinants of
performance reliability and/or behavioral errors result in secondary, additional workload. The
employees feel this kind of load as an attack on their psychical functions and processes, as
“straining” of their capabilities. These outer determinants represent direct hindrances in
perception and registration of information about the operation situation and consecutive solution
of the situation. Their negative influence on the employee is amplified by their “break through”
the employee. Thus, these determinants indirectly affect the individual ´s behavior, activities,
feeling , i.e. reliable performance as far as product quantity or quality and/or safety of operation
procedures is concerned. This second action of the above mentioned determinants causes
disorders of perception, disorders of attention and concentration, disorders of coordination of
motion, disorders of thinking and decision, disorders of the level of activity, disturbance of social
relations, whereby social relations act as one of the determinants of reliable or unreliable operator
´s performance.
Sources of secondary workload
Outer physical conditions
In the effort to eliminate negative and disturbing influences of the working conditions following
measures (found on the basis of safety analysis) should be taken:
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devoted to the optimization of the work environments (improvement of local and global
lighting, decrease of noise, optimization of microclimatic conditions, color of the
workplace, better utilization of colors with regard to the labor safety, improvement of
orientation on the workplace, reducing of the toxicity in the atmosphere, etc.
technical character (additional improvement of machines, adding of supplementary
technical devices ensuring increased labor safety, optimization of the working tools,
improvement of the personal protective equipment, etc.)
production character (change of the technological procedures, involvement of
automatization, mechanization, change of operation procedures, etc.)
esthetic character (improvement of the work environments in terms of an esthetic
organization of the workplace
In addition to the improvement of operator’s performance and labor safety at the workplace,
optimization of the work environments yields also improvement of the feeling of comfort at the
workplace and of the mental and physical health of employees.
Organizing and controlling factors
Organization of labor, shifts, time schedules, responsibilities, authorities, information flow,
communication, systems of adaptation of new employees, education courses of employees –
these are all areas, in which secondary workload can occur.
Interpersonal relations
Unsuitable interpersonal relations cause that the attention is not drawn to tasks, which should be
fulfilled, but to other directions. The consequence is irritation, over-sensitiveness, feeling of
discomfort, stress, dissatisfaction and higher incidence of illness and injuries. The influence of
psychosomatic aspects on the reliability and safety of working performance is equally important
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than the effect of action of physical factors, whether directly as an objective source of workload
or through a response in the psychical sphere as a subjective source of workload.
Depending on the quality of these factors of work environments, optimal or not optimal,
excessive workload will occur or the employee is able or not able to cope with this situation, or
avoid it. Thus, the individual can get in a vicious circle, in which the persisting objective sources
of workload with their negative consequences influence the working-performance preparation of
a human being and strengthen objective sources of workload.
Breakdown of equipment and not standard situations
In terms of operation safety it is important to train employees not only in the professional area,
i.e. to gain knowledge, skill and habits, but also to prepare individuals in the psychical area, i.e.
to maintain their adequate performance in nonstandard and stress situations. This should be an
integral part of accidents schedules and their training. The psychical training is devoted to the
diminishing and /or eliminating of anxieties or fears in case of not standard situations occurring
in running technological equipment. Unknown dangers are a greater psychical workload than
well-known dangers. If the employee gets successively familiar with the fact that the work
environment is a source of danger, but at the same time the individual does not know how to face
it, his/her consciousness is encumbered by factors, which are detriment in terms of mental
hygiene. Getting familiar with measures of protection against this danger, training and exercises
are not only a prevention of accidents and injury but also a mental hygienic action.
.
By neglecting prevention the requirements upon watchfulness of a person and his/her adaptability
to a risk situation increase. Safety labor requires human beings to adopt their activities to the risk
of a given situation. This adaptation, however, requires a good knowledge of specific danger on
the workplace. Labor performed at arbitrary danger always encumbers the human organism
psychically. To be conscious of danger does not always mean a perfect and watchful behavior,
but also fear, resignation and trust in fate. From this follows: each danger for an individual,
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though being aware of it and trying to carefully face it, is safety defective in terms of labor.
Prevention, which removes outer danger, is at the same time a mental hygienic prevention.
Possible solutions of the problem – safety management system (SMS)
In solving problems of labor safety and health protection the human factor is an integral part of
the above-mentioned system human being – production unit – work environments. Thus, it is
necessary to take this factor into account also in case of prevention of injuries and diseases
caused by the job and incorporate it into the overall system of safety and health prevention
management.
The SMS management system is a system of principles and measures necessary for fulfilling
prescriptions of labor safety and health protection at workplace, principles of protection of
employees at workplace, permanent improvement of working conditions and working discipline
and the overall performance of employees. If we mention the overall performance, we mean also
the performance reliability of the employee in terms of quality, quantity or safety. Thus, we mean
the human factor in the production process. We should take into account the fact that labor safety
and health protection at workplace do not represent only traditional prevention against injury and
accidents but also all aspects of protection of employees connected with labor – for example
physical and psychical comfort, social protection, working conditions, working relations,
hygienic conditions, social conditions at work place, etc (I. Majer, 2002). In individual steps of
incorporating the SMS management system also the requirement of integrated incorporation of
the human factor must be taken into account.
HUMAN RELIABILITY ANALYSIS IN SLOVAKIA
Many of the hazard evaluation techniques can be used to identify the potential for human-
fai1ure-caused accidents. What-lf/Checklist analysis may consider issues concerning the potential
for an operator error. HAZOP study frequently inc1ude general operator errors as causes of
process deviations. It can be say that, these hazard evaluation techniques can be used to address
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general human errors but on the other hand they tend to focus mainly on the hardware aspects of
potential accidents. When process operations inc1ude manual activities or when human machine
interface is very complex it makes difficult to use the standard hazard evaluation techniques to
evaluate the significance of potential human errors. Then it is clear that more specific method for
human factor evaluation, as Human Reliability analysis is needed. Human reliability analysis is a
systematic evaluation of the factors that influence the performance of operators, staff, technicians
and plant personnel. The primary purpose of human reliability analysis in the quantitative risk
analysis of chemical processes is to provide quantitative values of human error and to analyze the
characteristics of systems, procedures, and operators to identify likely sources of errors.
Quantitative assessment techniques of human error in chemical industries are used the same as in
nuclear power station in Slovakia – techniques THERP and TRC from SAIC
THERP
The Technique for Human Error Rate Prediction (THERP) (Swain and Guttman, 1983) is the
most widely used technique to date in nuclear power station in Slovakia. It is basically a hybrid
approach because it models human errors using probability trees and models of dependence, but
also it considers Performance Shaping Factors (PSFs) affecting the operator actions as:
Operating conditions.
Human abilities
Externally imposed factors
Time duration and fatigue
The technique is carried out in follow steps, each of which requires the performance of well
defined steps. These are namely :
Plant list
Review Information from fault tree analysis – check branches of fault trees for human
failures affecting the top event
Talk trough – familiarization with relevant procedures
Task analysis – break down tasks into smaller discrete units of activity such
Input information to human Evaluation processes Action to be taken Environments and constraints
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Tools and job aids Manpower Communications
Develop HRA Event Trees – express each unit task sequentially as binary branches of an
event tree. Each branch represents correct or incorrect performance
Assign human error probabilities – data provided in the handbook (Swain and Guttman,
1983)
Estimate the relative effects of performance shaping factors - data provided in the
handbook (Swain and Guttman, 1983)
Assess dependece - equation for modifying probabilities on the basis of dependence
between tasks provided the handbook (Swain and Guttman, 1983)
Determine success and failure probabilities – total probabilities for success and failures by
multiplying branch probabilities and summing appropriately
Determine the effects of recovery factors – operators may recover from errors before they
have effect, recovery factors are applied to dominant error sequences
Perform a sensitivity analysis
Supply information to fault tree analysis – human error probability or rate
The implicit classification of human errors, included in the data base of THERP, contains errors
that are all reducible to two error types:
1. Error of Omission, by which a step or an entire task are omitted.
2. Error of Commission, which entails selection errors, such as issuing the wrong command
or selecting the wrong control, and sequence errors, such as time errors, i.e. too early or
too late execution, or qualitative errors, i.e. too little or too much.
THERP uses the Human Reliability Analysis Event Tree as its basic tool. By the use of this tree a
graphical description of the procedural step in a task is set out in a logical framework, which
implies that, at each node of the tree, there is a binary decision point, representing the failure or
the success of the current action. Hence these trees are compatible with conventional system
event trees, they can be evaluated in the formal mathematical sense, and consequently, once the
success or failure probability of each particular task steps in a procedure is known.
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The key role of THERP is the determination of the probability that an error will result in a system
failure. This probability is assigned a value Fi. Branching trees are constructed to determine the
paths to system success and failure. The probability that an error will occur is given by Pi. FiPi is
the joint probability that an error will occur and that the error will lead to system failure. 1-FiPi is
the probability that an operation will be performed, which does not lead to system failure. The
probability that a class of errors will lead to system failure is given by:
(1)
where ni is the number of independent operations. The total system or subsystem failure rate is
given by:
(2)
where QT is the probability that one or more failure conditions will result from errors in at least
one of the n failure classes.
THERP allows the determination of the types, numbers, and skill levels of the personnel required
to operate the system. For system effectiveness, THERP allows an assessment of whether
uantitative requirements will be met. The determination of training requirements is more implicit
than explicit. Unacceptable task performance error rates suggest the need for training to improve
proficiency. Hence, THERP can suggest the need for training rather than specific training topics.
THERP can be applied to all types of equipments, tasks, and behaviors. With the aid of standard
human engineering techniques, it can be used for design analysis. Finally, THERP can be applied
to the early stages of system design as well as the later stages.
Table 1. Typical values of human error in nuclear power station in Slovakia evaluated by
THERP.
Code Description Probability value
OA(APR-PC) Operator doesn’t make fast decrease of pressure in PO - SGTR
5,0.10-2
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OA(APR-SC) Operator doesn’t make fast decrease of pressure in SO 3,0.10-1
OA(AF) Operator doesn’t open 1 from 2 relief valve 3,0.10-1
OA(CS) Operator doesn’t start condense pumps 5,0.10-2
OA(DM) Operator doesn’t start pumps for demi-water 0,4 MPa 5,0.10-3
OA(DRAIN) Operator doesn’t fill out channels to HZ 1,0.10+0
OA(DW) Operator doesn’t start pumps for demi-water 1 MPa 5,0.10-3
OA(EF) Operator doesn’t open valves in system SHNČ 5,0.10-3
OA(FWH-I) Operator doesn’t split HNK 1,0.10-2
OA(FWL-I) Operator doesn’t isolate feed pipe 1,0.10-2
OA(IFSL-I) Operator doesn’t isolate interfacing LOCA 2,0.10-3
OA(IM) Operator doesn’t open valves 5,0.10-3
OA(LP-OVERFL) Operator overflow storage tank TH 4,0.10-2
OA(MC-LOOP) Operator error to stop release from the loop 5,0.10-3
OA(RH) Operator doesn’t start RH system 1,0.10-3
OA(RH-ATM) Operator doesn’t open cooling system PSA 5,0.10-3
OA(SGTR-I) Operator doesn’t isolate loop SGTR 5,0.10-2
OA(SH-I) Operator doesn’t isolate HPK 5,0.10-3
OA(SL-I) Operator doesn’t isolate small release 5,0.10-3
OA(TB) Operator doesn’t start TB system 5,0.10-3
OA(TK50) Operator doesn’t open valve in the node TK50 5,0.10-3
OA(VSL-I) Operator doesn’t isolate very small release 5,0.10-3
OA(WM) Operator doesn’t start TK pump 5,0.10-3
OPER.PRE ACC Human error before accident 3,0.10-3
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TRC
Dougherty and Fragola (1988) have introduced the time-reliability correlation (TRC) system.
Basic input parameter for TRC method is time, which is available for the action related with
human error. This approach uses simulator training results to create a family of time-reliability
correlations, which are adjusted with either the Success Likelihood Index (SLI) or other expert
judgment methods to account for special conditions. TRC is the relationship between human
performance reliability and time. Data from simulators suggest that the lognormal distribution is
sufficient for modeling. The SLI is derived in the following manner:
(1) To choose the influences appropriate to the event and the situation.
(2) Rank the influences as multiples of the least important for a given situation, which is set
at "10."
(3) Sum the rankings of all influences and normalize the rankings to this sum.
(4) Assess the impact of each influence from best (1) to worst (10).
(5) Compute the "dot product" of the ranking and the quality vectors. This is the SLI.
(6) Apply the SLI. Mathematically, the SLI is expressed by:
(3)
and ri is the rank of the influence i and qi is the quality of the influence i. Dougherty and Fragola,
1998 focus on a lognormal TRC based on simulator data. This is in consonance with the modified
Human Cognitive Reliability (HCR), which was developed by Hannaman et al. 1984 for
calculating the operator probability of non-response to a cognitive processing task as a function
of time. The type of cognitive processing may be rule based, skill based, or knowledge based. For
task j, the probability of non-response P(t) is given by:
where Tmed is median time to perform the task corrected by a shaping factor Kj, bj is shape
parameter, Cgj is time delay factor as a fraction of Tmed for type j cognitive processing Cnj is scale
parameter as a fraction of Tmed for type j cognitive processing.
Furthermore the probability of human error which are generated by TRC methods can be
modified by the follows criteria: training situations, non-training situations (so called recovery)
and mental endurance.
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In the case of training situations the operator follows special and transient procedures and
also other relevant procedures for action performance. Non-training situations are characteristic
with non-availability of accurate and complete procedures or missing other relevant procedures
like specific criteria of operator intervention for action performance. Mental endurance has
negative influence at human performance mainly under stress and it should be combined with
non-training situations if do not exist any training situations. The probability of human errors
generated by TRC methods in nuclear power station in Slovakia is reviewed in tables 2-5.
Table 2 Probability of human error for training situations without operator uncertainty.
Time minSuccess Likelihood Index (SLI)
0,1 0,3 0,5 0,7 0,95 3E-1 2E-1 1E-1 6E-2 3E-210 9E-2 4E-2 2E-2 8E-3 3E-320 1E-2 5E-3 2E-3 5E-4 1E-430 3E-3 9E-4 3E-4 6E-5 1E-560 1E-4 3E-5 6E-6 1E-6 2E-7
Table 3 Probability of human error for training situations with operator uncertainty .
Time minSuccess Likelihood Index (SLI)
0,1 0,3 0,5 0,7 0,95 4E-1 3E-1 2E-1 2E-1 1E-110 2E-1 1E-1 9E-2 5E-2 3E-220 7E-2 4E-2 3E-2 1E-2 8E-330 3E-2 2E-2 1E-2 6E-3 3E-360 8E-3 4E-3 2E-3 9E-4 4E-4
Table 4 Probability of human error for non-training situations without operator uncertainty Success Likelihood Index (SLI)
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Time min 0,1 0,3 0,5 0,7 0,95 7E-1 5E-1 4E-1 3E-1 1E-110 3E-1 2E-1 1E-1 6E-2 3E-220 9E-2 4E-2 2E-2 8E-3 3E-330 3E-2 1E-2 5E-3 2E-3 5E-460 3E-3 9E-4 3E-4 6E-5 1E-5
Table 5 Probability of human error for non-training situations with operator uncertainty.
Time minSuccess Likelihood Index (SLI)
0,1 0,3 0,5 0,7 0,95 6E-1 5E-1 4E-1 3E-1 3E-110 4E-1 3E-1 2E-1 2E-1 1E-120 2E-1 1E-1 9E-2 5E-2 3E-230 1E-1 7E-2 4E-2 3E-2 1E-260 3E-2 2E-2 1E-2 6E-3 3E-3
The quantification of human error poses problems for a number of reasons:
Incident records rarely describe the environmental conditions (or performance shaping
factors) under which the human errors were made. This makes it difficult to generalize
from failure data for specific tasks to others that are similar.
Incident records often-record only errors, which have resulted in some modifiable
consequence. They do not record either opportunities for error or error frequencies with
no consequence (e.g. because of error recovery). It is not possible to determine, therefore,
what the true error rate is.
Some of the techniques for quantification of human reliability require the use of
subjective judgment by experts. Bias in making expert judgments and in judging error
probabilities for new designs of systems which have not yet been operated exacerbate the
problem, although progress has been made in 'structuring' the judgments in order to
reduce the bias.
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Without quantification of human factors, quantitative risk assessment reduces to an analysis of
hardware, predicated on an implicit assumption that all the human factors involved are about the
same as the industry average. This is usually a sensible assumption, because the quantitative risk
assessment is supposed to valid for the plant lifetime and operator performance will vary during
that time. However, it should be note that such an assumption is being made.
.
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Overview of information provide on human factors to Seveso II safety reports in Slovakia.
Identification of working positions, which can have influence at safety of system or subsystem;
Description and short characterization of working positions;
Analysis and human reliability assessment of certain working positions:
To indicate critical places in human – machine interaction
To summarize the set of human errors and they potential causes (HAZOP and the other
qualitative hazard techniques;
To provide quantification of human reliability assessment (quantitative technique is not
direct recommended);
Categorization/descriptions difficulties of subsystems (compound hardware, complex of start-up
or shut-down procedures and difficulties with communications);
To declare the system of people selection at working positions:
Physical health and to indicate the periodical monitoring;
Personal factors (mental health, self-control, resistance at stress)
To declare regular performance of next activities:
Ergonomics default
Default and uncertainty with software
Uncertainty and exact define responsibilities for operators
Undesirable workload
Undesirable rotation of working period
Non-favorable working conditions
Outside working influence – live style
To provide information about the risk which follows from their working activities
Training of hazard situation and emergency response
Level of communication in regular and critical situations
To collect information about needs, feelings and comments of workers/operators.
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Future development in Slovakia
It is clear that human reliability analysis techniques have been developed and applied in the
nuclear industry and there is an evident need to adapt these techniques to the chemical industry.
On the other hand, this it is not an easy goal because this requires the generation of human
reliability data appropriate to the chemical industry. Currently a few data exist but these data may
be inappropriate due to differences in environment, training, stress levels and etc. Direction of
improvement in the use of human factors methods in quantitative risk assessment in chemical
processes in Slovakia can be in:
Continued improvements in models for incorporating human factors into a quantitative
risk assessment in chemical processes.
Human factors analysis focus on the dynamical aspect of human – machine interaction
because, by the dynamical analysis, it becomes possible to consider specific sequences and
accident paths, which are not identified by the traditional way.
Better understanding of the impact of company and plant culture, management systems,
maintenance practices on the reliability of process plant equipment, in the case of modern plants,
the root causes of human errors can be effectively identified by the application of an accurate and
structured method that accounts for the cognitive processes in the management system.
To developed generally available data for human error.
Finally it can be said that human error is commonly found to be the dominant factor in
determining the frequencies of major incidents, thus uncertainty in estimating human error rates
may be the dominant factor in the uncertainty of the event frequency. On the other hand, it has to
be noted that the deep information can be also obtained by non-numerical descriptive type of
analysis, which is important for the evaluation of findings from the accident investigation and for
the assessment of the working and control procedures.
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References
Štikar, J.: - Hoskovec, J. - Stríženec, M.: Inženýrská psychologie, SPN, Praha 1982
Majer, I.: Príručka na zavedenie jednoduchého systému riadenia bezpečnosti a ochrany zdravia pri práci v malých podnikoch, Pravidlá dobrej praxe BOZP 1, NIP, Bratislava 2002
Swain, A. D., and H. E., Guttmann Handbook on Human Reliability Analysis with Emphasis on Nuclear Power Plant Application. NUREG/CR-1278. SAND 80-0200 RX, AN. Final Report, (1983),
Dougherty, E.M. and J.R. Fragola, Human Reliability Analysis, Wiley, (1988)
Hannaman, G.W., A.J. Spurgin, and Y.D. Lukic, "Human Cognitive Reliability for PRAAnalysis," NUS-4531, NUS Corp., 1984.