ISO/TR 23076:2021
(Main)Ergonomics — Recovery model for cyclical industrial work
Ergonomics — Recovery model for cyclical industrial work
This document establishes an ergonomic model for any cyclical human work planned and executed in an industrial competitive environment. It also covers the process of measuring work based on the concept of normal work performance and of the assessment of risk factors commonly associated with body postures, body or hand forces, manual material handling of loads and handling low loads at high frequency. This document applies to the adult working population and is intended to give reasonable protection for nearly all healthy adults. Those areas concerning health risks and control measures are mainly based on experimental studies regarding musculoskeletal loading, discomfort or pain and endurance or fatigue related to work organization and methods. The scope of this document is any cyclical human work planned and executed in an industrial competitive environment. The most typical cases are within industries where there is the need to define an expected output (products or services) based on the optimization of the trade-off between labour productivity and health and safety. The most sensitive organizations to this proposal are those within labour-intensive manufacturing industries with series and batch production systems: — automotive (original equipment manufacturer and tier 1 and 2 suppliers); — industrial automotive (trucks, buses, agricultural and mining equipment); — industrial manufacturing (small domestic and industrial equipment or machinery); — domestic appliances and consumer goods (white goods); — plastic and rubber products (tires, doors, windows, shoes); — consumer electronics (PCs, televisions, printers, radios, hi-fis, alarm systems); — furniture; — textiles and apparel; — food preparation; — packaging; — aerospace and defence; — rail and shipping; — large domestic and industrial equipment or machinery; — logistics.
Ergonomie — Modèle de récupération pour les activités cycliques dans l’industrie
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 23076
First edition
2021-10
Ergonomics — Recovery model for
cyclical industrial work
Ergonomie — Modèle de récupération pour les activités cycliques
dans l’industrie
Reference number
ISO/TR 23076:2021(E)
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ISO/TR 23076:2021(E)
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ISO/TR 23076:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Proposed approach . 5
4.1 The correct work content. 5
4.2 Design of a standard working method . 6
4.3 Work measurement . 7
4.3.1 General . 7
4.3.2 Standard work performance . 7
4.3.3 Real action . 8
4.4 Task assignment and work organization . 9
4.5 Biomechanical load measurement . 10
4.6 Ergonomic work allowance (EWA) . 11
4.6.1 General . 11
4.6.2 Traditional approach . 12
4.6.3 Proposed approach: EWA . 13
4.6.4 Design criteria . 18
4.7 Organizational solutions. 19
4.7.1 General . 19
4.7.2 Strategies to reduce the overall load index . 19
5 Ergonomic assessment worksheet (EAWS) .20
5.1 System overview .20
5.2 EAWS basic structure .20
5.2.1 General .20
5.2.2 Section 0: extra points . 23
5.2.3 S ection 1: body postures . 24
5.2.4 S ection 2: action forces . 25
5.2.5 S ection 3: manual material handling of loads . 26
5.2.6 S ection 4: repetitive motions of the upper limbs . 27
6 EWA effect on EAWS score.29
6.1 General .29
6.2 Effect of recovery time on typical workstations . 32
6.3 EAWS based EWA model . 33
Annex A (informative) EAWS scoring procedure .35
Bibliography . 144
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ISO/TR 23076:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 3,
Anthropometry and biomechanics.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/TR 23076:2021(E)
Introduction
0.1 General
The literature contains numerous methodologies for measuring physical stress in manual work.
Studies from different disciplines and research groups have concentrated on diverse external factors,
workplaces, and jobs. Factors most often cited include forceful exertions, repetitive motions, sustained
postures, strong vibration and cold temperatures.
The ISO 11228 series, ISO 11226 and ISO TR 12295 establish ergonomic recommendations for different
manual handling tasks, repetitive movements and working postures. They apply to occupational and
non-occupational activities and provide information for designers, employers, employees and others
involved in work, job and product design, such as occupational health and safety professionals.
— The ISO 11228 series relates to manual handling, including lifting and carrying, pushing and pulling
and the handling of low loads at high frequency.
— ISO 11226 gives recommended limits for static working postures with no or minimal external force
exertion, while taking into account body angles and duration.
— ISO TR 12295 serves as an application guide of the ISO 11228 series and ISO 11226 and offers a
simple risk assessment methodology for small and medium enterprises and for non-professional
activities. ISO/TR 12295:2014, C.5, is very relevant for this document, since there is a reference to
the EAWS system, which is extensively described in Annex A, being the first available ergonomic
tool meeting the requirements of the EWA model.
This document can be used by industrial engineers for the application of ergonomic work allowances
as a means to determine the correct quantity of cyclical work assigned to a worker in a manufacturing
plant in order to meet the definition of a fair day’s work. A fair day’s work is that length of working day,
and that intensity of actual work, which expends one day's full working power of the worker without
[26]
encroaching upon his or her capacity for the same amount of work for the next and following days .
In the old-fashioned production systems (piecework-based) the fair day’s work concept was used in
connection with the fair day’s wage. In this document, the studies about the definition of the fair day’s
work become fundamental to connect work-study with the most recent knowledge about biomechanical
load (occupational health and safety), with a special focus on the product-process design phase.
0.2 Recovery
In the field of ergonomics there is a special interest in predicting fatigue dependent on the intensity,
duration and composition of stress factors and to determine the necessary recovery time. Table 1 shows
those different activity levels and consideration periods, possible reasons for fatigue and different
possibilities of recovery.
Table 1 — Fatigue and recovery dependent on activity levels
Level of activity Period Fatigue from Recovery by
Work life Decades Overexertion for decades Retirement
Phases of work life Years Overexertion for years Holidays
Sequences of work shifts Months or weeks Unfavourable shift re- Weekend, free days
gimes
One work shift One day Stress above endurance Free time, rest periods
limits
Tasks Hours Stress above endurance Rest period
limits
Part of a task Minutes Stress above endurance Change of stress factors
limits
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In ergonomic analysis of stress and fatigue for determining the necessary recovery time, considering
the period of one working day is the most important. In this document, this type of recovery is named
“recovery external to the work cycle” and is defined in ISO 11228-3.
In case of cyclical industrial work, where awkward static body postures are relevant, a strategy to
reduce the stress level is to allow short recovery periods within each work cycle. This type of recovery
is named “recovery within the work cycle”.
The proposed model concerns the quantification of recovery periods within the work cycle and
considers recovery periods outside the cycle (normally defined as pauses) as an exogenous variable,
evaluated within the factors characterizing the work organization.
0.3 Purpose and justification
The industrial sector is one of the sectors with the highest global employment rate (22,5 % of total
employment). Despite this, the most recent research efforts about the definition of a fair day’s work
date back to the 1980s. In the last 20 years a lot of research has been carried out on the biomechanical
load and many new standards have been created.
This document is a first bridge between two different fields of knowledge: work study (industrial
engineering) and occupational health and safety (ergonomics). the objective is to improve the work
study tools by leveraging the knowledge made available by the most recent studies about work-related
musculoskeletal disorders (WMSDs).
This document provides a methodological reference for the procedures to determine the fair quantity
of work within a working day in industrial operations with repetitive manual work cycles.
The goal of the model is to guide industrial engineers to keep the biomechanical load or local muscle
fatigue generated by the planned cyclical work within the limits defined in the ISO 11228 series and
ISO 11226.
This document proposes neither new work measurement techniques nor new ergonomic techniques
or standards. Rather, it aims at merging the best available knowledge (industrial engineering and
ergonomics) about human capacity of accomplishing a manual task, following a pre-defined work cycle
(method description and related standard time) without generating an excess of biomechanical load
(fatigue).
Present issues:
— Ergonomic allowance is neglected or assigned based on a partial evaluation of the physical load
(usually body postures and forces). The calculation is not influenced by:
— load duration (action frequency and duration of static actions);
— work organization (shift duration, duration and distribution of the break periods) and work
measurement.
— Lack of a well-recognized standard work performance to measure manual work.
— Available ergonomic evaluation systems work on different measurement scales and the difficulty of
assessing the overall physical stress.
— The ergonomic approach tends to be used reactively in the industry rather than proactively
(preventive ergonomics).
0.4 Expected benefits
— Support the adoption of the ISO 11228 series and ISO 11226 in the industrial manufacturing sectors.
— Support the definition of a standard work performance to standardize the work measurement.
— Improve working conditions, safety and ergonomics of workers in manufacturing industries.
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— Complement the traditional set of experts’ capabilities on time and motion with the ergonomic
skills necessary to design safe and efficient work stations and sustain continuous improvements in
productivity and ergonomics during the entire product life cycle.
— Support the ergonomic evaluation in the earliest stages of product or process development, when
changes are still feasible and the cost of such changes is affordable (preventive ergonomics).
— Link ergonomic improvements with labour cost reduction (improve ergonomics – reduce costs –
justify investments in ergonomic improvements).
— Reduce cost and deviation of the ergonomic risk-mapping process by linking the biomechanical load
measurement with work measurement and organization.
— Be an objective reference for employers and unions when setting up gainsharing contracts based on
labour productivity (industrial relations).
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TECHNICAL REPORT ISO/TR 23076:2021(E)
Ergonomics — Recovery model for cyclical industrial work
1 Scope
This document establishes an ergonomic model for any cyclical human work planned and executed
in an industrial competitive environment. It also covers the process of measuring work based on the
concept of normal work performance and of the assessment of risk factors commonly associated with
body postures, body or hand forces, manual material handling of loads and handling low loads at high
frequency.
This document applies to the adult working population and is intended to give reasonable protection
for nearly all healthy adults. Those areas concerning health risks and control measures are mainly
based on experimental studies regarding musculoskeletal loading, discomfort or pain and endurance
or fatigue related to work organization and methods.
The scope of this document is any cyclical human work planned and executed in an industrial
competitive environment. The most typical cases are within industries where there is the need to
define an expected output (products or services) based on the optimization of the trade-off between
labour productivity and health and safety.
The most sensitive organizations to this proposal are those within labour-intensive manufacturing
industries with series and batch production systems:
— automotive (original equipment manufacturer and tier 1 and 2 suppliers);
— industrial automotive (trucks, buses, agricultural and mining equipment);
— industrial manufacturing (small domestic and industrial equipment or machinery);
— domestic appliances and consumer goods (white goods);
— plastic and rubber products (tires, doors, windows, shoes);
— consumer electronics (PCs, televisions, printers, radios, hi-fis, alarm systems);
— furniture;
— textiles and apparel;
— food preparation;
— packaging;
— aerospace and defence;
— rail and shipping;
— large domestic and industrial equipment or machinery;
— logistics.
2 Normative references
There are no normative references in this document.
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3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
basic motion
manual motion performed with fingers, hands, arms, eyes, feet, legs or body, no longer decomposable as
regards to content time
3.2
technical action
elementary manual action to complete operations within the cycle basic motion in which a segment of
the upper limb (shoulder, elbow, wrist or finger) is involved to reach a target or to hold an object or a
posture
EXAMPLE Grasp, reach, move, turn, apply pressure, hold, turn, push or cut.
3.3
real action
combination of basic motions (technical actions) performed to achieve a finite and planned state of an
object
EXAMPLE Get and place an object, place a tool, activate (reach and press a button), micro finger cycle as
fastening a screw with fingers.
3.4
standard work
work with the most efficient method to produce a product (or perform a service) at a balanced flow to
achieve a desired output rate
3.5
standard working method
method to break down of the work into elements (operations), which are sequenced, organized and
repeatedly followed
Note 1 to entry: Standard conditions as part presentation, distances, geometries, weights or tools and equipment
are clearly described.
3.6
work measurement
application of techniques designed to define the time for a qualified worker to carry out a specified job
at a defined level of performance
3.7
standard work performance
effort level that could be easily maintained year in, year out, by a worker with average physical
capabilities, without drawing upon his or her reserves of energy
Note 1 to entry: Working at standard performance brings the worker to the end of the fair day’s work without an
excess of physical stress.
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3.8
time allowance
time added to the basic time
Note 1 to entry: The amount of the allowance depends on the nature of the work and the working environment,
and it is often assessed using an agreed set of guidelines and scales.
Note 2 to entry: Time allowances are used to cover personal needs, technical and organizational planned losses
and learning effect. This document refers to time allowances meaning the additional time to recover from an
excess of fatigue generated by the work cycle.
3.9
basic time
time set through a given work analysis system
Note 1 to entry: Predetermined time measuring systems (e.g. methods-time measurement) provide basic times
of manual elementary motions (e.g. reach, grasp, move).
Note 2 to entry: Basic time does not include any allowance.
3.10
standard time
time required by an average skilled operator, working at a normal pace, to perform a specified task
using a prescribed method
Note 1 to entry: The difference between standard time and basic time is that basic time is the time when work
should be done without any delays. Standard time is the time taken by the worker to complete the work with
some unavoidable and therefore planned delays (time allowances).
Note 2 to entry: Standard time includes time allowances.
3.11
methods-time measurement
MTM
procedure which analyses any manual operation or method into the basic motions required to perform
it and assigns to each motion a basic predetermined time, which is determined by the influencing
factors under which it is made
Note 1 to entry: Examples include reach or move distance, type of grasp, object weight.
3.12
cycle time
time available at each workstation to accomplish the tasks assigned for each unit of output
Note 1 to entry: Cycle time corresponds to the pace at which an assembly line delivers its output.
Note 2 to entry: In the case of a single workstation, cycle time and standard time coincide, since there is no idle
time caused by the imperfect synchronization of a sequence of workstations (balancing losses).
Note 3 to entry: Cycle time is expressed as the sum of standard time and idle time.
3.13
task assignment
line balancing
manufacturing-engineering technique, in which the production line operations are divided into tasks,
which are assigned to the minimum number of workstations
Note 1 to entry: A production line is said to be in balance when every worker's task takes approximately the same
amount of standard time. Well-balanced lines minimize labour idleness and improve productivity.
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3.14
work organization
way that tasks are distributed among the individuals in an organization and the ways in which these
are then coordinated to achieve the final product or service
Note 1 to entry: Work organization typically encompasses the total shift duration, the quantity and distribution
of the breaks, the type of man-machine interface and the level of allowed flexibility.
3.15
worker saturation
percentage of non-idle time within a cycle time
Note 1 to entry: Worker saturation is expressed as the fraction of standard time and cycle time.
Note 2 to entry: See Figure 1.
Key
CT cycle time
T time
A, B workstation A, B
1,2,3,4,5 operation 1,2,3,4,5 (basic time)
AA, BB allowance A, B
IT idle time (unsaturation)
1 + 2 task assigned to work station A (standard time)
3 + 4 + 5 task assigned to work station B (standard time)
Figure 1 — Industrial engineering terminology
3.16
biomechanical load
physical stress acting on the body or on anatomical structures within the body
Note 1 to entry: Loads originate from the external environment (e.g. the force generated by a power hand tool) or
are the possible result of voluntary or involuntary actions of the individual (e.g. lifting objects).
EXAMPLE Kinetic (motion), kinematic (force), oscillatory (vibration) stress and thermal (temperature)
energy sources.
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3.17
transition time
duration of the movements for changing from one body posture to another
3.18
overall load index
OLI
index compounding the overall biomechanical load generated by the different types of physical stress
4 Proposed approach
4.1 The correct work content
The determination of the correct work content for a given activity is a fundamental task for a company
in order to be competitive on the market, as well as to safeguard workers’ health and to guarantee a
proper quality of the performed activity. The setting of a standard time of a manual task is based on the
following steps (see Figure 2; T is the cycle time and T is used to indicate the standard time):
c std
a) design of a standard working method;
b) work measurement;
c) task assignment and work organization;
d) biomechanical load measurement;
e) ergonomic work allowance calculation (applying the model).
Key
input
process
output
Figure 2 — Standard time setting process
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4.2 Design of a standard working method
The design of a standard working method is the key driver to achieve operational excellence in levels of
productivity and safety. This task is one of the main responsibilities for industrial engineers, who have
to blend wisely several fields of knowledge to coordinate humans, machines and materials to attain a
desired output rate with the optimum utilization of energy, knowledge, money and time. It employs
key techniques (such as floor layouts, personnel organization, time standards, wage rates, incentive
payment plans, production scheduling) and technologies (ICT, digital devices, data and analytics) to
control the quantity and quality of goods and services produced. The design and planning of a working
system largely determines the ergonomic conditions of the worker and therefore it is fundamental to
bring the ergonomic knowledge into the earliest stages of the product and process development process
and the ergonomic constraints into the planning process (see Figure 3).
Figure 3 — Preventive ergonomics in the new product development process
To achieve such a sophisticated level of product or process development and planning process, the most
advanced industrial companies use a predetermined motion-time system (PMTS). A PMTS is a set of
data of elementary human motions, of which a basic time is predetermined, which is used as a reliable
language to design, plan and measure a manual task.
The last developments among available PMTSs aim at creating specific tools for designing work systems
in the earliest stages of product and process development, rather than simply measuring them once they
are up and running. In this way, it is possible to find the most efficient and ergonomic solutions when
it is still feasible to make product and process changes and the cost of such change is still affordable
(metal has not yet been cut). Indeed, in the early phases of product or process development, investments
in tools and equipment have usually not yet been released and changing a CAD file or a design is not too
expensive. Standard times play a key role in setting transformation process costs and purchasing costs
of goods an
...
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