AISH Rules and Advises for Workstations design

1
AISH Ergonomics memorandum
Environment Health and Safety integration
Ergonomics Rules and Advises for workstation
design
2
Introduction
The purpose of this document, which addresses to
methods/engineering teams, is to provide a set of
good practices informing and reminding some AISH
standards to be applied. In the case where
belgian regulations go beyond AISH standards and
recommendation, the belgian rules apply.

• Document management
• These rules result from experience and are based
  on standards in force or in preparation. They are
  complemented by our experience feedback.
• Ergonomic studies
• AISH considers employee safety as one of the
  main elements of its sustainable development
  policy and its sole objective is to reach ZERO
  ACCIDENT.
• Application of these rules contributes to
  improving working conditions but does not exempt
  from activity ergonomic analysis in response to
  specific needs.

• Ergonomic as part of the Health Safety
  management system

• Ergonomics of each working situation must be
  assessed

3
Introduction
4
Contents

• Noise ....p30
• Thermal environment...p32
• Anti-fatigue mats...p33
• Workstation feeding. .......p35
• Picking and material handling ......p37
• Pedestrian and forklift traffic.........p38
• Zones of vision .....p41
• Position of controls .....p45
• Footswitch utilization ..p46
• Two-hand controls ..p48
• Office work ........p50

• Workstation Accessibility......p5
• Choice of working posture...p7
• Choice of seat ..p9
• Choice of footrest p13
• Working zones .p15
• Workstation dimensioning ......p17
• Working height and worktop ...p19
• Body movement recommendation.. ...p21
• Manual handling - Carrying load .p23
• Exerted forces ..p26
• Illumination....... p28

5
Workstation Accessibility

• Recommendations
• Avoid all obstructions in the hand placement
  zone.
• Use containers facilitating parts pick-up
  (dispensers, shallow boxes, etc.).
• Provide enough space for pulling seat back to
  allow operator to easier leave the workstation.
• Round corners of jigs forming recesses with
  which operator will be in frequent contact
• Assembly or product volume can cause congestion
  problems in this case, a suitable solution
  should be sought (lifting table, rotating platen,
  etc.).
• Ensure dimensioning of accesses and traffic
  corridors around workstation in relation to
  movements to be undertaken (parts delivery,
  trolley usage, passing of one or several people).
  
• Leave free passageways (provide storage and
  holding areas).
• Material crossing flow can be avoided by using
  workstation gravity skate wheel conveyor,
  operators movements will be reduced.

Provide a minimum of space to prevent all
operator movements from collision and obstruction
6
Workstation Accessibility
?
Hand access Outstretched hand Fist
no wrist rotation L minimum (mm)
120 120 H minimum (mm)
60 120 with wrist
rotation ? minimum (mm) 120
120
7
Choice of working postures

• Definitions
• Posture ?
• Load ?
• High-seated
• workstation ?
• Supported standing ?
• workstation
• Recommendations

• Posture is a body attitude adopted by or imposed
  on the operator during his activity.
• ? seated ? high-seated ?
  supported standing ? standing
• Mass of parts lifted, conveyed and positioned.
• Workstation allowing operator to work either
  seated or standing
• Workstation equipped with a seated-standing seat
  supporting up to 60 of the operator weight.

8
Choice of working postures

• Posture is the first factor to be defined, other
  workstation factors should be defined with
  respect to posture.
• The most frequent strain factor is the working
  posture set according to the workstation design.

Workstation
Work performed within areas at arm's reach
Work performed on large horizontal and/or
vertical surface or with bulky objects
Low force requirement for handling light objects
High force requirement for handling heavy objects
Sufficient legroom
Insufficient legroom
Special working height requirements
Standing
Supported standing
Seated
High-seated
Posture to be used for precision work
9
Choice of a seat

• Foreword The choice of the seat will depend on
  
• - task constraints
• - posture flexibility
• - ease to sit and stand
• - seat stability required
• - material covering
• - ease to be adjusted
• Seat lightness and compactness facilitate
  application of Lean Manufacturing principles
  (workstation changing and mutual assistance)
• Seated and high-seated positions
• Recommendations
• Working seat should be easily adaptable to each
  user's specific needs.
• Seat section should provide support and avoid
  discomfort due to seat pressure on the rear side
  of the leg.
• Material used should prevent sweat accumulation
  and electrostatic discharge production.
• Back rest, adjustable in height and inclination,
  should allow back muscles to relax.

10
1) Seated and high-seated
positions Seat should be suited and adaptable
to work situations and persons
Choice of a workshop seat
DIMENSIONS TO BE RESPECTED (mm) Seated
High-seated mm inches
mm inches A ? Adjustable seat height
450 - 560 18 - 22 750 850 30 -
33 B ? Seat depth 380 - 420 15 -
17 380 420 15 - 17 C ? Seat
width 400 - 500 16 - 20 400 500 16
- 20 E ? Backrest height 200 - 320
8 - 13 200 320 8 - 13 F ? Backrest
width 350 - 400 14 - 16 350 400 14 -
16 Y ? Adjustable backrest height 170 -
215 7 8 170 215 7 8 M ?
Adjustable footrest height 400
560 16 22 Backrest must be free inclining and
depth adjusting. Seat section must be
forward inclining.
11
Choice of a seat

• 2) Supported standing position
• A saddle-leaning seat should be provided only at
  workstations at which a permanently seated
  position or a combined seated and standing
  position cannot be used.
• Advantages of a saddle-leaning seat
• it supports up to 60 of body weight
• it facilitates changing to the standing
  position.
• Drawbacks of using a saddle-leaning seat
• localized pressure and restricted blood
  circulation
• legs tend to swell after a while
• working positions are restricted.
• Recommendations
• When the work to be performed is at outstretched
  arm's reach, there must be sufficient space for
  the knees and legs. When this space is not
  provided, arm reach distances are less than those
  available in a normal standing position.
• A saddle-leaning seat
• should be in the form of a saddle or its seat
  section should incline forwards and its depth
  should be relatively shallow.
• should be easily adjustable.

12
Choice of a seat
Saddle-leaning seat

• A height adjustable from
• 630 to 840 mm (25 to 33)
• ? inclination adjustable from 0 to 15

This seat should never be utilized permanently
for high-seated position Pains in the back and
in the shoulder could break out after few hours.
13
Choice of Footrest

• Recommendations
• A footrest is incompatible with a supported
  standing workstation. It is mainly used with a
  seated or high-seated workstation.
• The bearing surface should be antislip.
• Height adjustment is compulsory given individual
  size differences
• For workstations with foot controls, it is wise
  to integrate such controls into the footrest to
  obtain a common height adjustment.
• The footrest should be built into the
  workstation or should adhere sufficiently to the
  floor.
• The seat used at a "seated-standing" workstation
  can be equipped with a footrest allowing the
  operator to change posture.

A footrest cannot be utilized with a
saddle-leaning seat . It could be utilized only
with a seated or a high-seated position
14
Choice of Footrest
A footrest is essential beneath a "high-seated"
workstation and desirable beneath a "seated"
workstation to allow leg support.
DIMENSIONS TO BE RESPECTED seated
high-seated
mm inches mm inches H ? Adjustable
height 40 - 150 2 6 300 450 12 - 18 L
? Width gt500 gt20 gt500 gt20 P ?
Depth gt350 gt14 gt350 gt14 Y ?
Adjustable inclination 0 - 15 0 - 15
15
Working zones

• Definitions
• Comfort zone .
• Acceptable zone
• Arduous zone .
• 2-hand zone .

• ? Zone of maximum comfort when handling parts
  and tools.
• Part assembly must be performed in this zone. .
• ? When the comfort zone is insufficient (e.g.
  assembly workstation), this space can be used
  for feeding and discharge operations as well as
  occasional control actuations or assembly
  operations, whose repetitiveness is less 10 times
  /hour (6 min. cycle time).
• ? Restricted working zone to be avoided
• ? Zone in which work can be performed by either
  hand or both hands without particular restriction
• particulières.
• ??Portion of space within which the operator's
  points of support and reach are distributed
  during activity.

Sufficient clearance must be provided to ensure
lower limb mobility, to allow operator to sit
properly in front the working zone and to work in
good seated posture.
16
Working zones
Define position of parts and tools to be handled
based on using them according to required zones
1170 maximum (46) condition concerning body
movements can extend this zone
When undertaking assembly requiring body movement
precision, it is recommended that the 2-hand zone
be centered at an average distance of 200 mm from
the table edge (150 - 250 mm)
17
Workstation Dimensioning

• Clearance for passing legs and feet beneath
• Recommendations
• Sufficient clearance should be provided to
  ensure lower limb mobility
• Worktop thickness should not hinder the operator
  at thigh level. In practice, a 30 mm thick
  worktop often provides an acceptable compromise
  between the spatial requirement and strength
  properties.
• Clearance width beneath workstation should allow
  operator to swivel his seat without encountering
  obstructions
• Clearance depth beneath workstation should be
  sufficient to allow operator to sit properly

Workstation dimensioning should enable operator
to adopt a suitable posture
18
Workstation Dimensioning
19
Working Height and worktop

• Definitions
• Working height means hand height in the working
  position
• Worktop height means the height of the product
  or sub-assembly bearing level during assembly.
• Recommendations
• Working height should be chosen to ensure an
  appropriate body position, whilst meeting vision
  requirements.
• This choice represents a compromise between
  requirements for low neck, arm, shoulder and back
  loads and vision distance requirements ensuring
  appropriate visual control.
• Optimum working height and inclination depend on
  the task to be performed.
• A worktop can be inclined or horizontal. An
  inclined surface often provides the best
  solution the most suitable angle for an inclined
  surface represents a compromise between vision
  requirements, the imposed load on the neck, back
  and shoulders and the angle preventing objects
  from falling. An angle of approximately 15 is
  recommended for many precision handling tasks
  involving significant vision requirements
• Precision work features a high visual load
  (vision distance of the order of 30 cm -12),
  accurate positioning (P2 and P3 - reference MTM)
  and a millimetric degree of accuracy (1.2 cm-1 -
  reference MTM), this constraint appearing for at
  least 30 of the cycle time.

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Working Height
Main postures description
Task requirement Office work Manual work (arm support) coordination associated with visual surveillance in same working area Active arm or small object movements Handling of objects that are large but not too bulky or heavy
Position
Working height H1 700 à 750 mm 28 to 30 H2 1100 à 1200 mm 43 to 47 H3 1000 à 1100 mm 39 to 43 H4 800 à 1000 mm 31 to 39
Worktop height Worktop at elbow height Worktop above elbow height Worktop at elbow height Worktop below elbow height
In transfer lines interlinked at constant height,
working height can vary depending on assembly
choice of working height can only be a compromise
based on the working situation.
21
Body movement recommendations

• Definitions
• Body movement ?
• Repetitiveness ?
• Recommendations
• Prohibit awkward posture (extreme joints
  position). Limit force and repetition, which can
  lead to fatigue and discomfort. Operating
  procedure should be analyzed to take these 3
  parameters into account the design phase.
• In the case of repetitive work, organize task
  changes to require different body movements
  during the day. Favor short, frequent breaks
  (period during which muscles do not contract), to
  allocate recovery time.
• Reduce length and number of movements and use
  movements creating continuous curves rather than
  sharp angles.

• All postures and movements required to perform a
  task.
• Defined as a work operation or activity frequency
  (number of parts/hour, number of tasks/cycle,
  number of forces/cycle, etc.).

Consider limits and human variability, listen to
employees to gain insight to potential problems
and to gain knowledge from worker experience. Job
rotation helps to reduce worker fatigue by
varying the body positions and reducing the time
spent doing the same repetitive motions.
22
Body movement recommendations
Repetitive movements
When defining operating procedures, try to limit
extreme postures and repetitive movements.
Consider exerted forces, movement combinations
and their combined effect on the worker.
!

• Avoid using the hand and the hand palm as a
  hammer (blows), pliers (forces), press (prolonged
  bearing).
• Avoid the use of prolonged static forces and
  forces applied by wrist rotation or extreme
  angular positions.

23
Manual Handling - Carrying Loads
Frequent lifting and carrying loads can lead to
fatigue and to injuries to the shoulder and the
back.

• Recommendations
• Wear protective clothing, if appropriate, such
  as
• lightweight, flexible, tear and
  puncture-resistant clothing
• safety shoes with toe caps and slip resistant
  soles
• protective gloves appropriate to the materials
  being handled
• Prepare to lift by assessing the weight of the
  load, the distance it will be moved and ensure
  the route is free of obstacles
• stand close to and face the load
• get a good grip on the load and lift
• keep the load close to the body as possible
• Avoid lifting up the load with a twisting or
  side bend motion .
• initiate the lift with body weight
• lift smoothly without jerking
• maintain an S curve in your spine

Manual material handling can present risk to the
worker. Review job tasks requiring lifting to see
if the load can be moved using a conveyor, a
hoist or with the use of a lifting device.
24
!
Manual Handling - Carrying Loads
25
!
Manual handling - Carrying Loads
Moving a load from one point to another, whatever
the picking up and setting down heights. Carrying
loads can include both lifting and conveyance.
Definition Carrying Loads

• Load carrying limits -
• 18 45 year old man 25kg max.
• 18 45 year old woman 16.5kg max.

- Repetitive load carrying Conveyed tonnage
limits - Load carried on a distance 20 meters
10 t/day for men 5 t/day for
women Load carried on a distance gt 20 meters
5 t/day for men 2.5
t/day for women
To be used Loads carrying Abacus
26
Exerted Forces
Work station efforts Effort limits calculation
concern actions on parts, tools or controls. It
is a quantitative tool to assess the onerousness
of a task / activity.

• Determining the effort limit
• Choose the reference letter in Table 1.
• Read the curves in Table 3.
• Apply the correction rules in Table 2.

Example 1 A worker have to lift a 9kg load 45
times/hour. Is it acceptable ? 1 -gt we choose the
reference letter M 2 -gt we read on the table just
after 3 -gt we multiply the result by 2 as the
worker use his both hands. ACCEPTABLE
Example 2 A worker have to push a 60kg trolley
once each 5 minutes. Is it acceptable ? 1 -gt we
choose the reference letter L 2 -gt we read on the
table just after 3 -gt we multiply the result by 2
as the worker use his both hands. NON ACCEPTABLE
27
Exerted Forces
Limit forces to be exerted to recommended values
The Effort (in daN) column expresses the maximum
effort that can exerted by the majority of the
working population (95 of men and 80 of women)
and by physically-challenged persons.
Example 1 The hourly frequency is 45 in the
X-axis and intersecting with M. We obtain 4.5 daN
(4.5kg) Result x 2 9 kg ACCEPTABLE
Example 2 The hourly frequency is 12 in the
X-axis and intersecting with L. We obtain 5.8 daN
(5.8kg) Result x 2 11.6 kg NON ACCEPTABLE
28
Illumination

• Good lightning is a quantity of sufficient light
  and a good distribution of illumination for
  visual comfort. It is a factor of security and
  quality in terms of visual performance.
• Definitions
• Illumination ?
• Luminance ?
• Contrast ?
• Recommendations to ensure visual comfort

Light emission received by a surface (lux or
lumen/m2). Flux reaching the effective plane
depends on the nature and intensity of the source
and factors involving reflection from surfaces
surrounding the worktop Measurement of luminous
appearance of a lighted surface (brightness) or
of a surface emitting in a given direction
(candela/m2) amount of light received by the
eye. Subjective assessment of the difference in
appearance between two visual field parts seen
successively or simultaneously .
Good general overhead lighting should be in place
before assessing the need to install individual
task lighting.
29
Illumination
Comply with the following recommendations to
ensure a good illumination level

• Recommended values excl. natural lighting
• Illumination level corridors and stairs E
  100 - 200 lux 9 18 foot-candles
• Illumination level packing area, warehouses E
  200 - 400 lux 18 37 foot-candles
• Illumination level assembly of medium-size
  parts E 500 - 750 lux 37 69 foot-candles
• Illumination level assembly of small parts,
  inspection E 750 - 1000 lux 69 92
  foot-candles
• Illumination level assembly of very small
  parts E 1000 - 2000 lux 92 185 foot-candles
• General / local lighting ration Eg gt El / 3
• Luminance contrast in central part of visual
  field 0.3 lt E1 / E4 lt 0.9
• Luminance contrast between peripheral and
  central 0.5 lt E3 / E4 lt 0.8

• Lighting homogeneity

• Dazzle
• elimination

N
N
N

• Contrasts
• between object and immediate background

High Medium
Low
Too much light can generate uncomfortable glares
and unbalanced illumination.
30
Noise
!

• Noise trauma depends on three factors noise
  intensity, frequency and exposure time
• Definitions
• Noise ?
• Parameters used to evaluate hearing risk
• LEX,8h ? daily noise exposure level in dB(A)
• time-weighted average noise exposure level for a
  nominal 8-hour working day (integrating all
  noises at work including impulsive noise).
• LPC ? peak acoustic pressure level
• maximum value of instantaneous acoustic pressure
  measured with frequency weighting C at the
  worker's ear.
• L EX,8h ? weekly noise exposure level in dB(A)
• time-weighted average of daily noise exposure
  levels for a nominal week comprising five 8-hour
  working days.
• Practical recommendations for reducing noise

air vibration generated by one or several sounds,
which causes a work disturbance and leads to
irreversible partial or total perception deafness
above a certain dose. Its intensity is expressed
in dB(A) sound level corrected with respect to
human ear sensitivity.
Noise can have negative physiological and
behavioral effects on workers.
31
Noise
!
Recommended exposure values in workshops LEX,8h
lt 80 dB(A) and/or Lpc lt 135
dB(C)
Forbid any Ototoxic substance use in workshops
Recommended noise level during acceptance
inspection at machine-tool supplier Daily noise
exposure LEXd lt 70 dB(A) Peak acoustic
pressure Lpc lt 120 dB(C)
Recommended noise level in offices Daily noise
exposure LEXd lt 55 dB(A)
Ambient noise levels (dB) allowing conversation
depending on distance between speakers. Dist.
between Speakers 0.35m (1.2 ft) 1m
( 3.3 ft) 2m (6.5 ft) 3m (9.8 ft)
Very loud voice 80 70
65 60 Normal voice 70
60 55 50
Noise level should allow for verbal communication
requirement and task complexity
32
Thermal Environment

• Thermal environment should be adapted to human
  physiological characteristics
• Definition
• Thermal comfort ?
• Recommandations
• Ventilation
• Generally an air renewal rate of 2 volumes/hour
  minimum is sufficient for rooms with a known
  atmosphere.

Results from environmental characteristics and
individual's physiological condition.
33
Anti-fatigue Mats

• Definition
• Anti-fatigue mats ? Designed to reduce
  fatigue that is caused by standing for a long
  period on hard surface.
• Recommendations
• Considering the use of a mat
• Anti-fatigue absorb the shock due to walking
  on hard surface
• Non-slip according to the risk .
• Protection object fall
• Isolation cold, vibrations and noise
• Those factors should be taken into account when
  choosing a mat.

34
Anti-fatigue Mats
Be careful, Anti-Fatigue Mats could be
Electrostatic Electricity Generators
35
Workstation feeding
Recommendations

• Limit forces according to requirements given in
  Exerted forces section
• Limit load to be conveyed according to
  requirements given in "Carrying loads" section
• Allocate a minimum of necessary space for
  movements and displacements according to
  requirements given in "Accessibility" section
• Favor use of parts storage on inclined surfaces
• Use containers facilitating part pick-up (limit
  wrist flexion)
• Use mobile trolleys for moving parts without
  carrying them, provide handling aids for heavy
  (gt12kg 21lbs) or bulky loads
• ?Arrange heaviest loads, within the authorized
  transportable limit, at a height between 800 and
  1500 mm 31 to 59
• Use dynamic storage units allowing front
  pick-up
• Train personnel to material handling
  prescriptions

Prohibit use of a stepstool or stairs for
accessing shelves. A ramp could be utilized to
facilitate lifting and lowering parts, products
or boxes.
36
Workstation feeding
Line side and storage layout Height indicated
height of the hands

• Space available for picking up containers or
  parts
• E1 E2 100 mm minimum for handling
  containers,
• E1 150 mm if parts are to be picked up from
  inside containers.
• Maximum pick-up depth "P"
• 300 mm with respect to shelf edge.
• Minimum height
• don't place parts or containers to be frequently
  handled on the floor,
• if necessary, leave enough space to crouch when
  lifting them.

37
Picking and Handling
A picking operation is done for the part
replenishment using the  little train  (parts
transport system), for the kitting of parts to
manufacturing cells and for kitting of customer
orders
Recommandations

• Parts bulky and / or heavy gt 12kg
• Parts should be put on a pallet on the lower
  level of a rack, preferably at the waist level.
• Utilize material handling equipment whenever
  possible
• Allocate a material handling zone at least 2x
  larger than the part to be handled.
• Boxes, containers lt 12 kg
• Provide enough room for the hands to access the
  container
• Prefer boxes with coverage (American boxes) to
  banish any cutter use.
• Getting parts from containers lt 12 kg
• Provide enough room for the hands, avoid
  extensive wrist flexion
• Wear personal protective equipment to prevent
  cuts caused by carton edges
• Do not cover the containers that are used
  frequently.
• Utilize gravity skate wheel conveyor or other
  means to ensure parts do not move crosswise or
  jam during handling.
• Cut-resistant gloves and grabbers or lifters
  must be provided for handling of large sheet
  metal.
• Specifications for handling equipments
• safe operating and maintenance procedure
• clearances to move loads
• capability to bear the load
• required personal protective equipment
• Shelves and bays could bear at least 4 time the
  weight of the container or the part put down on
  it.

Operator must be prepared (clear and easy access,
good grip, arms straight, stand close to the lift
) before lifting or handling heavy and /or bulky
parts or containers (gt12kg ).
38
Pedestrian and powered vehicles traffic

• Recommendations
• Aisle should provide the shortest practical
  distance between work areas
• Aisles must be marked with traffic paint or
  edging material, .Pedestrian traffic aisles must
  be clearly marked
• Ensure floor is level to prevent materials or
  moving vehicles from toppling, maintain in good
  condition
• Keep the aisles clear of obstacles or of
  equipment element overhanging
• Marked and indicate the visitor walk ways and
  light up the walking zones
• Allow enough room for vehicles to back and turn
  around
• Provide mirrors to avoid blind corners and
  intersections. .

Define the aisle dimensions for a powered vehicle
to back and turn around according to the turning
radius specification.
39
Pedestrian and powered vehicles traffic
For equipment maintenance the traffic height
should be gt 450 mm
All pedestrian access and walking corridors must
be clearly identified with the pedestrian
pictogram and clearly separated from powered
vehicles ways.
40
Pedestrian and powered vehicles traffic width
of factory aisles
41
Zones of vision

• Definitions
• Main vision axis ?
• Visual comfort zone ?
• Acceptable zone ?
• Arduous zone ?
• Recommendations

Eye-product to be assembled axis Zone around
main vision axis vision can be displaced within
this zone by moving the eyes only. Zone in which
small head movements are required to allow vision
to identify a component. This zone can be used
when the comfort zone is insufficient. Zone
only to be used under certain conditions (e.g.
light signal accompanying acoustic signal). Major
head movements are required to scan this zone
The reliability to detect defects through visual
inspection varies substantially from inspector to
inspector. Poka Yoke must be implemented to
either prevent defects or automatically reject
defects.
42
Zones of vision
Respect visual range zones defined by main vision
axis determined by most frequent working zone
V
A ? Product being assembled B ? Visual
indicator to be viewed at each cycle C ? Cyclic
feeding of parts required for product assembly V
? Power screwdriver
43
Zones of vision Visual Range

• Visual range ?
• Recommendations
• The viewing direction and the "eye task"
  distance can have an adverse influence if they
  are inadequately considered or if examination of
  their interaction is overlooked.
• Avoid repeated head movements required for
  reading indicators. Preferably, position these
  indicators in the visual comfort zone with
  respect to the main vision axis and limit
  placement of objects to be picked up to the
  "acceptable zone".
• Eye product distance should not exceed 50 cm
  (20) for assembly operations involving small
  parts or requiring precision.
• For reading purposes, eye character distance
  is defined according to script dimensions.
• Vision zone depth should be determined with
  respect to size of items to be read or
  recognized.

Response characteristic to the task visual
requirement. It is defined by the viewing
direction and the "eye - task" distance.
Visual requirements can cause postural constraints
44
Zones of vision Visual Range
Visual range distance and size of components to
be viewed should be defined according to the
following rules
e line thickness L character
width H character height D eye to
character distance
45
Positioning of controls

• Recommendations
• Manual controls used at each cycle should be
  located in acceptable gripping zones.
• The degree of force to be applied should be
  considered, when determining the position of
  controls requiring application of force (e.g.
  press lever).
• Controls used frequently should always be
  located near the visual task.
• A control used for emergency operation should be
  capable of actuation in a very short time.
• When a control requires only a single hand,
  position it on the side of the limb required.
  Provide means of adjustability to satisfy
  right-handed / left-handed operation if possible.
  
• Controls should have a low probability of being
  actuated accidentally. Ensure body movements
  (amplitude and direction) are compatible with
  required arm movements.
• Controls should located according to
• expected operator response time
• potential of emergency reaction (activate
  E-stop)
• operator learning curve

Arrangement of controls can minimize postural
constraints but in some cases can increase the
risk of identification errors. Controls must be
protected if they could be accidentally activated.
46
Foot Switches

• Recommendations
• Use of foot switches at each cycle can increase
  task arduousness if the following basic rules are
  not followed
• ?Heel must maintain contact with the floor or
  footrest
• Large leg movements should be avoided
• Multiple foot positions should be available on
  foot switches
• Foot switches should be able to be positioned in
  relation to individual
• If two foot switches are utilized on a
  workstation they must be positioned so that there
  will be no risk of error
• Utilization of safety shoes should be consider
  in the design of the foot switches allowed
  enough toe room to properly activate the switch
• Utilize manual controls if possible. Foot switch
  should be a secondary choice

Foot switches must be protected if they could be
accidentally activated. Frequent use of foot
switches in a standing position can cause
postural constraints
47
Foot Switches
Foot switches must be protected if they could be
accidentally activated. Frequent use of foot
switches in a standing position can cause
postural constraints
48
Selection and layout of two hand control
Definition
? Two hand control a device requiring a least
one simultaneous action using both hands to
trigger and maintain, as long as a dangerous
situation exists, all machine operations and
which therefore constitutes a protection measure
only for the person who actuates it.
Recommendations

• Use of horizontally positioned "mushroom head"
  pushbuttons (type XB Telemecanique)
• Fingertip pressing should be prohibited for
  repeated operation.
• Control devices should be stable under normal
  operation.
• When calculating the safety distance between
  operating devices and danger zones, take into
  account
• - hand/arm speed,
• - control shape and layout,
• - device response time,
• - time between signal interruption and risk
  disappearance.

The set of recommendations should be complemented
by accurate analysis of the work situation and
consideration of relevant standards. Two hands
controls are utilized to protect the operator
from accident . To protect employees passing by,
screens or other guardrails must be provided.
49
Selection and layout of two hand control
Define two-hand control position based on risks
of reaching danger zones

• Clear spacing of controls (L) 550 mm.
• Positioning of controls on a horizontal or
  virtually horizontal surface positioned at least
  1100 mm above the floor (H).

• In the case of non-repetitive work only, fit a
  protection collar around operating controls
  mounted on a vertical or virtually vertical
  surface.
• If control spacing is less than 550 mm, use one
  or more screens ensuring the controls cannot be
  simultaneously touched by a device comprising a
  300 mm long (Ø lt 5 mm) rigid rod and a 250 mm
  long cord. Rod represents the forearm and cord,
  the hand. Apply this device in every possible
  position.

50
Office Work
Office layout and equipments must be designed
according to the work organization, the technical
requirements, and to the human characteristics.

• Recommendations
• Office layout
• Position work so that verbal communication will
  be possible.
• Allocate enough room to facilitate access
  (minimum 80 cm , behind a desk 120 cm
• Lighting should be evenly distributed throughout
  the workplace and should not create glare or
  shadows. A maximum of 500 lux is recommended when
  the operator is working on a computer..
• Limit the noise at an acceptable level (50dbA
  max.) use sound-absorbing material such as
  antistatic carpeting, curtains, sound-absorbing
  ceiling material.
• Utilize pleasant colors (mat or satin, no gloss
  paint)
• Utilize adequate furniture, desk worktop suited
  to requirements (recommended 80 x 120 cm), seat
  with 5 bearing points and castors, back rest and
  seat adjustable in height and inclination
• Space allotment
• Flexible layout, pre-wiring (framed floor or
  baseboard), sound absorbing removable partition
• Space optimized, single or shared work space
• Facilitate communication with other offices or
  departments
• Facilitate traffic with adequate corridor width
  and common equipment sites
• Windows

An ergonomic assessment should be conducted
before designing or re-designing an office area
(work requirement and operator activity) .
Assessment should be shared with the workers to
gather input.
51
Office Work
52
Useful Links

• American Industrial Hygiene Association -
  www.aiha.org
• Canadian Center for Occupational Health Safety
  - GB / FR www.ccohs.ca
• Cornell University Ergonomics
  www.ergo.human.cornell.edu
• Department of Energy - www.hhs.energy.gov
• European committee for standardization
  www.cenorm.be
• Human Factor Ergonomics Society of Australia
  www.ergonomics.org.au
• Human Factors and Ergonomics Society -
  www.hfes.org
• International Ergonomic Association www.iea.cc
• International Labor Organization ILO-OSH2001
  www.ilo.org
• International Organization for Standardization -
  GB / FR www.iso.org