Ergonomics - Atlas Copco

EXTERNAL LOAD
For evaluation purposes, it is assumed that
the tool is being used for line assembly in
the car industry at a workstation where it
is used on horizontal surfaces. The installed
torque is assumed to be 28 Nm. The height
is adjusted to allow a comfortable posture
for counteracting the horizontal pull force
from the torque reaction. The tool is not
suspended in a balancer. It is picked up
from the tool rest with one hand, resulting
in a radial flexion torque. It is also operated
with one hand when tightening. Thus a
Male operators
Female operators
palmar flexion torque will load the operator
during tightening. When the tool is posi-
tioned on the bolt head a supination torque is
required to hold the tool as it enters the bolt.
It is assumed that both male and female
operators use the workstation. Therefore two
evaluations of external load are made, one for
male operators and one for female operators.
Real loads can be calculated as follows:
Trigger force is measured to 4 N with
the air inlet connected,
Table 4.16 Evaluation of external load for the Angle Nutrunner LTV29 R30-10.
Evaluations are given for both male and female operators.
On soft joints the installed torque will
give a reaction force (pull back) on the
Force/Torque MVC Safety factors Reduced Real load Real / Score
N/Nm Speed Frequency Duration MVC N/Nm Reduced
Trigger 380 N a1=0.8 a2=0.6 a3=0.8 148N 4 N 0.03 0
Pull back 400 N 154 N 104 N 0.7 6
Palmar fl exion 15 Nm 6 Nm 3.1 Nm 0.5 4
Radial fl exion 15 Nm 6 Nm 1.4 Nm 0.2 2
Supination 15 Nm 6 Nm 1.4 Nm 0.2 2
Total score: 14
Force/Torque MVC Safety factors Reduced Real load Real / Score
N/Nm Speed Frequency Duration MVC N/Nm Reduced
Trigger 245 N a1=0.8 a2=0.6 a3=0.8 92N 4 N 0.04 0
Pull back 300 N 131 N 104 N 0.9 14
Palmar fl exion 10 Nm 4 Nm 3.1 Nm 0.8 7
Radial fl exion 10 Nm 4 Nm 1.4 Nm 0.4 4
Supination 10 Nm 4 Nm 1.4 Nm 0.4 4
Total score: 29
163