Ergonomics - Atlas Copco

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Real external load After the MVC has been reduced, the re- maining permissible force or torque should be compared with the real external load. If this load is not known, it can be measured – for example, trigger forces for pneumatic tools connected to an air line. Machine group Average force (N) Spread±(N) Grinders 60 40 Drills 150 100 Chipping hammers 120 60 Riveting hammers 100 50 Nutrunners 50 20 Screwdrivers 50 20 Table 3.9 Typical feed forces for different machine groups. Push and feed forces are not easy to measure in a process. Table 3.9 provides estimated feed/push forces for different machine groups. It is self-evident that the forces involved increase in proportion to the power of the machine used. The spread value provided confirms this fact. Evaluation of external load The purpose of the evaluation is to com- pare calculated permissible load on the operator with the real load. Score 40 30 20 10 0 0 From the tables in the preceding chap- ters the MVC for different load types can be found. This MVC is then reduced according to the recommendations above. Finally the R-value for each load is calculated by dividing the real external load by the reduced MVC. The score for that external load can then be obtained from the figure below. This pro- cedure should be followed for each external load present. The total score is the sum of the scores for the individual loads. 0.5 1 Fig. 3.7 The score for external load can be obtained from this figure, using the R-value for each type of external load present. 1.5 R-value 81
82 Comments for different tool types In this section the different types of tools are discussed. A tool can be used in an infi- nite number of different ways and the load on the operator is unique for each situation. The discussion below can therefore only be used as a rough guide, giving an indication of what to think about when the load on the operator is estimated. Normally, more powerful tools require more force. This can be taken into account choosing a force within the spread given in the table. When the trigger time per day for an operation is not known, Table 3.10 can be used as a guide. Machine Total duration Spread ± type (hours/day) (hours) Grinders 3 1.5 Drills 1 0.5 Chipping hammers 2 1.5 Riveting hammers 1 0.5 Screwdrivers 2 1 Impact wrenches 1 0.5 Impulse nutrunners 2 1 Angle nutrunners 2 1 Stall torque nutrunners 1 0.5 Table 3.10 Typical durations in hours per day for different machine groups. Grinders The important external loads when handling a grinder are the feed force and the trigger force. The feed force is typically a combina- tion of a standing push-down or push-for- ward force and an ulnar-flexion torque. For tools operated with two hands the torque and forces can be calculated if the torque is estimated to be equal for both hands and the influence of the mass of the tool is disregarded. This will lead to calculated forces that are 0-50% too high. For pneumatic tools the force in the support handle is normally about 70% of the total feed force and for electric tools it is about 80%. The ulnar-flexion torque can be estimated as the force in the support handle multiplied by the horizontal distance from the center of the support handle to the point on the wheel where the downward force is applied. For tools operated with one hand the feed force equals the force in the hand and the ulnar-flexion torque is the feed force multiplied by the distance from the center of the hand to the point on the wheel where the force is applied. Trigger force can be measured. Depend- ing on the type of trigger, the trigger force is distributed over the fingers.
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Power Tool Ergonomics E V A L U A T
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Acknowledgements While doing resear
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How to get the best out of this boo
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Work with international standards I
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Good ergonomics is good economics W
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10 SOCIOLOGY INDUSTRIAL SOCIOLOGY S
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12 Work organization No organizatio
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1 outside the production system, an
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1 A seated operator usually has goo
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1 without stretching the trunk. The
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20 The arm sling as a preventive me
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22 Extreme working postures in real
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2 Working with high feed forces req
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2 Working areas of a standing works
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2 body is lifted or tilted, or the
Page 31 and 32: 30 The team is an important factor
Page 33 and 34: 32 Grinders Grinders and sanders ar
Page 35 and 36: 34 HanDle DeSiGn The hand grips on
Page 37 and 38: 36 DUSt anD oil Although the machin
Page 39 and 40: 38 Working environment In general,
Page 41 and 42: 40 SHoCK reaCtion Sudden changes in
Page 43 and 44: 42 practice. Sometimes the chisel h
Page 45 and 46: 44 SHoCK reaCtion These tools do no
Page 47 and 48: 46 heavy, assembly work is often hi
Page 49 and 50: 48 depends on its inertia. The same
Page 51 and 52: 50 bolts. Unfortunately there are a
Page 53 and 54: 52 The low reaction torque in impul
Page 55 and 56: 54 the working environment A typica
Page 57 and 58: 56 Today, the angle nutrunner can b
Page 59 and 60: 58 High torque nutrunners for use w
Page 61 and 62: 60 Wheel nuts on trucks and buses a
Page 63 and 64: 62 Introduction A basic ergonomic p
Page 65 and 66: 64 Handle design The handle of a ha
Page 67 and 68: 66 Arteries Veins (superficial) Vei
Page 69 and 70: 68 Handle size Since a tool handle
Page 71 and 72: 70 However, if the texture is too c
Page 73 and 74: 72 Bibliography Chaffin, D.B. and A
Page 75 and 76: 74 Fig. 3.3 The same feed force app
Page 77 and 78: 76 Pushing and pulling Pushing a to
Page 79 and 80: 78 the object, the shape of the obj
Page 81: 80 Safety factor a 2 Frequency of t
Page 85 and 86: 84 The trigger is either operated b
Page 87 and 88: 86 used in one handed operations. T
Page 89 and 90: 88 Weight The weight of a hand-held
Page 91 and 92: 90 stability of grip, the center of
Page 93 and 94: 92 Temperature Hand-held power tool
Page 95 and 96: 94 To ensure physical comfort durin
Page 97 and 98: 96 Score 40 30 20 10 0 Bibliography
Page 99 and 100: 98 the dynamic properties of the ma
Page 101 and 102: 100 High motor power and fast clutc
Page 103 and 104: 102 Score 40 30 20 10 0 shock react
Page 105 and 106: 104 piezo-electric crystal. When th
Page 107 and 108: 106 EN 50144 and EN 60745. Both ISO
Page 109 and 110: 108 hole of the wheel are wider tha
Page 111 and 112: 110 In the GTG 40 grinding machine,
Page 113 and 114: 112 RRH machines serves two functio
Page 115 and 116: 114 be noted that declared values b
Page 117 and 118: 116 Noise Noise was the first envir
Page 119 and 120: 118 value for 8 hours’ exposure t
Page 121 and 122: 120 We can start by looking at the
Page 123 and 124: 122 This is done with a minimum inc
Page 125 and 126: 124 microphones at a distance of 1
Page 127 and 128: 126 coated with dust or damaged by
Page 129 and 130: 128 This method has not been used b
Page 131 and 132: 130 tool cabinet. Many workplaces h
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132 lubrication. Made from a compos
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134 Grinder GTG 40 F085 The relevan
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136 were simulated by fitting a whe
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138 Drill LBB 26 EPX-060 The releva
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140 applied to the center of the dr
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142 Chipping hammer RRF 31 The rele
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144 SHOCK REACTION There are no sho
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146 Riveting hammer RRH 06 The rele
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148 WEIGHT The weight is 1.3 kg, sc
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150 Screwdriver LUM 22 PR4 The rele
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152 This gives a score of 9. In pra
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154 Impulse nutrunner EP9 PTX80-HR1
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156 Due to friction in the hydrauli
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158 Electric nutrunner ETP ST32-05-
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160 WEIGHT The electric nutrunner i
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162 Angle nutrunner LTV 29 R30-10 T
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164 operator equal to installed tor
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166 Electric angle nutrunner Tensor
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168 WEIGHT The electric nutrunner i
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170 High torque nutrunner LTP 51 Th
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172 Score 40 30 20 10 0 NOISE The d
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Ergonomics - Atlas Copco

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