HIRARC : TASK ANALYSIS

TASK ANALYSIS

Working Environment

·         Material- Flammable, Toxic, oxidizing, corrosive

·         Systems- Units, Equipments, Instruments, etc

·         Process / Operation

·         Human

Hazard Identification

·         Material- Dow’s FE&I, CEI, ISI

·         Systems-  FMEA, FMEACA

·         Operation / Process- HAZOP

·         Human- Task Analysis

Human at Work

Work may be done by Rule based or Skill based. Conscious behavior is being used whenever task is being learned- rule-based behavior as rules are developed on how to do the task. Unconscious behavior, generally known as skill, takes over once complete proficiency is attained.

At work people try for as long as possible to control demands on their resources using skill-based behavior- they can work for several hours without unacceptable fatigue. When the situation requires more analytical reasoning, as when incidents occur, they switch to rule-based or conscious behavior

Human Error

Past worldwide records of major accidents of industrial facilities shows that many of those accidents were caused by human error of either plant  operators or maintenance contractors(Lees, 1996). An error is often the end-point of a complex series of events involving failures associated:

·          with the process and system

·          the procedures and practices

·          communication systems

·          Etc

Error is more likely due to:

·          failure to provide adequate resources and training.

·          inadequate management and supervision

·          working conditions are not optimal,

·          pressure on the operator to make a correct

·         decision is high due to any cause

·          Unfamiliar conditions and lack of technical back-up and information

An error may be defined as the failure of planned actions to achieve their goals. Error:

·          Violations

·          Mistakes

·          Slips

·          Mismatched

TERMINOLOGY

Violation- an intentional departure from accepted practice.  example not wearing a hard hat.

·         a hat is hot to wear

·         it is getting in the way

·         less comfortable than being bare-headed

·         a hat may not be readily available

Slips- errors in automatic skill-based or unconscious behavior. example  Slips occur when actions are not as planned.

Mistakes;

·         errors in conscious behavior which may be either rule-based, if the task merely involves following a set of procedures, or knowledge-based when the task involves evaluation of a new situation.

·         Mistakes arise when planning is inadequate.

·         Mistakes due to lack of knowledge

·         They may lack elementary knowledge of the properties of the materials, the process or the equipment.

·         They may believe they must always follow rules, and be unable to react correctly when flexibility is needed

·         People may be given contradictory or ambiguous instructions. Also instructions may have implied contradictions

Conscious behavior is being used whenever task is being learned - rule-based behavior as rules are developed about how to do the task. Error: Mistakes. Unconscious behavior, generally known as skill, takes over once complete proficiency is attained.  Error: Slips. Intentional deviation from rules, procedures, standard practice.  Error: Violation.

Example

Ahmad drove his car southbound along PLUS highway. He was enjoying his drive at 145 km/h and was not wearing seat belt. Between Ayer Keroh R&R and Exit, he had a flat tyre. While preparing to replace the flat tyre, he found that there was no spare tyre.

·         What is the task

·         Violation??

·         Mistakes??

·         Slips??

Three pipes (A,B and C) are utilized to transfer flammable gas. Pipe B required maintenance work. An operator in the control room pressed the wrong button which isolated pipe A instead of pipe B. A team of maintenance contract workers removed a

flange connection at pipe B, flammable gas was released and ignited by one of the contractor worker who was smoking.

·          What is the task

·          Violation??

·          Mistakes??

·          Slips??

TASK ANALYSIS

A process of sorting out what people might or actually do when carying a task. The analysis try to respond to relevant questions:

·          what actions do the operators carry out?

·          how do operators respond to different cues in their environment?

·          what errors might be made and deviations caused in plant operations?

·          how might any error be recovered from, or any deviation be controlled?

·          how do operators plan their actions?

Task analysis helps in the prevention or reduction in the frequency of occurrence of error. Task Analysis has been developed as a systematic method for analyzing a task into its

·          goals

·          operations

·          Plan

·          Procedure

·          practice

A goal is what the person doing the job is aiming to achieve-  A specific work objective. A task is a specific work assignment- represents the set of operations / actions required to achieve a stated goal. The operations represent the stages involved in the task. Plans describe the methods and conditions under which the operations are carried out.

A procedure is a step-by-step description of how to proceed from beginning to end in order to perform a given task. A practice is a set of guidelines helpful to the performance of a specific type of work which may not always follow a set procedure.

Task Analysis can provide input to such features as:

·          the specification of equipment, controls, emergency controls and process interface;

·          the preparation of procedures and operating instructions;

·          the development of written practices;

·          the specification of training requirements and development of skills

Types of Task Analysis

·         Hierarchical Task Analysis (HTA) -  Graphical / Tubular representation - Decomposition of high level task into constituent subtasks, operations, plans

·         Cognitive Task Analysis -  Model the internal representation and processing that occurs for the purpose of designing tasks that can be undertaken more effectively by humans

·         Modeling “how to” knowledge - Focuses on task to action mapping.  GOMS approach (Goals, Operations, Methods, Selection Rules)

Example of Tubular / textual HTA

0. Clean the house

1.0 Get the vacuum cleaner out

2.0 Fixed the appropriate attachment

3.0 Clean the rooms

3.1 Clean the hall

3.2 Clean the living rooms

3.3 Clean the bedrooms

4.0 Empty the dust bag

5.0 Put the vacuum cleaner and the attachments away

Plan 0: do 1-2-3-5 in that order. When dust bag full do 4

Plan 3: do 3.1, 3.2 and 3.3 in any order depending on which rooms need cleaning

DATA FOR TASK ANALYSIS

Data / Information required

·         documentation process diagrams, functional models, job descriptions, working practices and permits, instructions, operating manuals, design specifications, existing documentation of task; . output from hazard reviews;

·          Hazard reviews

·          study of plant records, computer output, logs, etc

·          debriefing of operators following completion of the task

Information required

·          discussion or interview with management, actual or potential users, design, engineers, safety specialists and human factors experts;

·          observation, recording and inspection during operation and user trails including use or video, audio, transcripts, coding schemes.

STEPS IN CARRYING OUT A TASK ANALYSIS

Goal of the analysis;

·         The overall goal of the task to be carried out should be stated

·         Examples: To ensure adequate supply of raw materials for a processing unit

·         Task - a specific work assignment that represents the set of operations / actions required to achieve a stated goal. Examples (1) To schedule arrival of raw material supply truck; (2) To fill raw material storage tank; (3)  To pumping of raw material to processing unit

Breakdown of the task into steps or activities

·         The task is then broken down into a set of subordinate tasks or operations which must be per-formed to achieve the goal at that level

·         to list all the steps which are critical for performing the task correctly

Creating a plan

·         A plan should refer to each of its subordinate operations.

·         Plans are important in defining when to carry out various operations, their sequence, the duration of an activity, the process conditions and so on.

·          The plan might take the form of a hierarchical diagram (flow diagram) or a tabular list.

Analyzing the plan. The analysis of the plan or system should:

·         examine possible deviations from the system

·         detemine the likelihood of those deviations

·         determine any deviation at the start and end of the procedure

Modifying the plan

·         Modifications should be made to improve the method of working and to reduce the effect of deviations and appropriate controls, precautions and mitigation introduced

·         The analysis of the plan leads to improvements in such features as working methods, procedures and practices, work environment and exposure frequency, communication and information processing, skill and capabilities of people, and management, supervision and control

·         The plans should also give advice on action to take when deviations arise and recovery as necessary including such features as: (1)what to do if the transfer of material is to the wrong place or if it is off-specification; (2) how to effect immediate recovery from human error or equipment malfunction; (3) The plan must be properly documented with appropriate performance standards, practices and procedures clearly identified.

·         The plans should also give advice on action to take when deviations arise and recovery as necessary including such features as: (1) A procedure should therefore start by indicating the task purpose and features of importance; (2) Practices should present positive guidelines for correct performance.

THE STRUCTURE OF PLANS

A plan might involve several different types of method:

·          in a set or fixed sequence- the person follows a set of activities in a specific order

·          in a timesharing sequence- the operations are carried out in co-ordination with each other or at the same time

A plan might involve several different types of method:

·          in a branching sequence- the person will do a task, then depending on the outcome from that task, the individual will carry out a particular option;

·          a plan may allow for the selection of the task which is most appropriate to the situation.

Example 3

Prepare a plan for changing a flat tyre on a car. It can be assumed that the ground is level, the spare tyre is properly inflated and the car is not in a hazardous location. Each task could be expanded with respect to action if problems in performance occur.

ANALYSIS OF TASK DEVIATIONS

There are many ways of analyzing task deviations. The traditional method study approach employs (What?, When?, How?, Where?, Who?, Why?).  The objective is to improve safety, production and quality with possible savings in cost. Example of questions in analysis of task deviations?

·          Is the task to be performed within the operator's ability?

·          Does the task place excessive demands upon the operator?

·          What environmental concerns must be addressed for this task?

·          What potential emergencies can arise, and can the operator recognize them?

·          Is needed information displayed and/or available?

·          Will the operator know what to do with the information?

·          Will the operator be able to control the system?

·          Does this task require further study or decomposition?

CRITICAL TASK

Safety Risk ; SR = 2(S+ L)

·         Negative values is treated as zero

Severity: 1 to 5

Likelihood: -5 to 0

·         10-5 to 100 per year

Production Lapse

·         values range from –2 to 2

·         10-2 to 102 per year

Quality Lapse

·          Similar basis as in production lapse

Critical Task: CT=SR+PL+QL

Example 4

A batch storage tanks system for storing flammable liquid is shown in Figure1. The tank is 5 m high. Further protection and operating aids provided are:

·         Low level alarm (LAL) at 0.5 m,

·         High level alarm (LAH) at 4.1 m

·         a trip system closing valve FV2 and high high level alarm (LHH) at 4.2 m.