NIOSH Lifting Equation 1991

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NIOSH Lifting Equation (1991)
RWL LC x HM x VM x DM x AM x CM x FM

• RWLRecommended Weight Limit
• (LC) 23kg (51 lb)
• (HM) Horizontal Location
• (VM) Vertical Location
• (DM) Distance of Lift
• (AM) Asymmetry
• (CM) Coupling
• (FM) Frequency

1981
Action Limit LC x Hf x Vf x Df x Ff Max
Permissible Limit 3AL
LC (40 kg) x Hf (Horizontal dist.) x Vf
(Vertical dist.) x Df (Distance moved) x Ff
(Frequency lifts)
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HM 25/H
HM 10/H

• H horizontal Location
• mid-point of the line joining the inner ankle
  bones to a point projected on the floor directly
  below the mid-point of the hand grasps (ie., load
  center).

Even less than 25 is considered as 25 cm
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HM (1-(0.003abs(V-75))

• V vertical Location
• vertical height of the hands above the floor
• V is measured vertically from the floor to the
  mid-point between the hand grasps, as defined by
  the large middle knuckle

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VM (1-(0.003abs(V-75))
VM (1-(0.0075abs(V-30))
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DM (0.82(4.5/D))

• D distance in vertical travel
• vertical travel distance of the hands between the
  origin and destination of the lift.

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DM (0.82(4.5/D)) DM (0.82(1.8/D))
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AM (1-(0.0032A))

• A Asymmetry Angle
• defined by the location of the load relative to
  the worker's mid-sagittal plane, as defined by
  the neutral body posture, rather than the
  position of the feet or the extent of body twist
• NIOSH assumes that no pivoting or stepping occurs.

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AM (1-(0.0032A))
The location of the load relative to the workers
midsagittal plane
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Frequency Factor
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FM based on F, D, V
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Coupling FactorCM
GOOD 1.0
POOR.90
FAIR 1.0 or .95

• defined as handles or hand-hold cut-outs of
  optimal design
• For loose parts or irregular objects, (not
  containerized) a "Good" hand-to-object coupling
  would be defined as a comfortable grip in which
  the hand can be easily wrapped around the object

• as handles or hand-hold cut-outs of less than
  optimal design
• 2. For containers of optimal design with no
  handles or hand-hold cut-outs or for loose parts
  or irregular objects, a "Fair" hand-to-object
  coupling is a grip in which the hand can be
  flexed about 90 degrees

• Containers of less than optimal design or loose
  parts or irregular objects that are bulky, hard
  to handle, or have sharp edges
• 2. Lifting non-rigid bags (i.e., bags that sage
  in the middle.

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D
V
H
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1 is the best

• Lfixed

Task variables change
Load change

• Task variables fixed

• If LI increases the level of strain for a given
  work increases

• LI can compare the relative severity of two job

• LIgt1 means the potential risk of LBP

• LIgt3 Automaiton

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HM 10/H
VM (1-(0.0075abs(V-30))
DM (0.82(1.8/D))
18in
D
AM (1-(0.0032A))
Vd
V
15in
Activity is symmetric Fingers at 90 degree in
origin Good control needed in Destination
Activity 2 per min Duration is less than 1.5
hours
Ho
20in
Hd
10in
19
30
20
15
10
33
18
0
0
2
1.5
fair
30
.5
.89
.92
1
.84
.95
16.66
18in
1
.98
.92
1
.84
.95
39.6
D
33in
Vd
30
1.8
V
16.66
30
.76
Ho
15in
39.6
20in
HM 10/H
VM (1-(0.0075abs(V-30))
Hd
DM (0.82(1.8/D))
10in
AM (1-(0.0032A))
20
30
15
25
8
35
10
0
0
2
1.5
good
30
10in
.67
.96
1
1
.84
1
27.55
D
1
.96
1
1
.84
1
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Vd
V
35in
30
1.09
27.55
30
.73
41
25in
Ho
15in
HM 10/H
VM (1-(0.0075abs(V-30))
DM (0.82(1.8/D))
Hd
AM (1-(0.0032A))
8in
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L44lb
HM 10/H
VM (1-(0.0075abs(V-30))
DM (0.82(1.8/D))
AM (1-(0.0032A))
Activity is symmetric Fingers at 90degree in
origin Good control needed in Destination
Activity one per Shift Duration is less than 1
hour
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origin
HM 10/230.43
VM (1-(0.0075abs(23-30)) 0.89
DM (0.82(1.8/43))0.86
AM (1-(0.0032A))1

• Activity is symmetricgtA0
• Load is irregular and Fingers at 90degree in
  origingood
• Good control in Destination because of the design
  of the machineFair
• Activity one per shift so Flt0.2
• Duration is less than 1 hour

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Horigin15in
35lbs Roll of paper from cart
Loading supply rolls
Activity is symmetric and no twist Both hands in
front of body Significant control needed in
Destination and hand can not be flexed Activity
4 per shift Duration is less than 1 hour
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HM 10/150.67
VM (1-(0.0075abs(27-30)) 0.98
DM (0.82(1.8/17))0.93
AM (1-(0.0032A))1
Activity is symmetric and no twistA0 Both hands
in front of body Significant control needed in
Destination and hands can not be flexed poor
Activity 4 per shift0.2 lifts/min Duration is
less than 1 hour
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Can we adapt the cart so that the paper rolls
could be easily pushed into position on the
machine, without manually lifting them? If not
gt Make the roll smaller It gets the load
closer to the body Raise the height of the
destination to increase the VM Improve the
coupling to increase the CM
Can not be changed
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Mixing hopper
Loading bags into a hopper
-Without moving his feet, he twist to the right
and pick up a bag off the hand truck. In one
continuous motion he then twists to his left to
place the bag on the rim of the hopper. A sharp
edged blade within the hopper cuts open the bag
to allow the contents to fall into the
hopper. -Activity 1-12 times per shift lt.2
lifts/min for less than 1 hour -Significant
control not required at origin and Destination,
fingers can flex about 90degrees, the bags are
semi rigid, they do not sag in the middle fair
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Dish Washing machine Uploading
-A worker Manually lifts trays of clean dishes
from a conveyor at the end of a dish washing
machine and loads them on a cart. The trays are
filled with assorted dishes and silverware.
-Activity 5 lifts/min-between 45 min to 1
hour -Significant control not required at origin
and Destination, fingers can flex about
90degrees good
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Successes (Waters, 1993 Garg, 1989)

• Combined 4 disciplines of science
• Asymmetry incorporated
• Easy to use
• Measure factors independently
• Conservative estimates
• Focuses on the biggest problem
• Growing scientific literature review

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In summary, the Revised NIOSH Lifting Ewuation
does not apply if any of the following occur

• Lifting/Lowering with one hand
• Lifting/Lowering while seated or kneeling
• Lifting/Lowering in a restricted work space
• Lifting/Lowering unstable objects
• Lifting/Lowering while carrying, pushing or
  pulling
• Lifting/Lowering with wheelbarrows or shovels
• Lifting/Lowering with high speed motion (faster
  than about 30 inches /second)
• Lifting/Lowering with unreasonable foot/floor
  coupling (lt0.4 coefficient of friction between
  the sole and the floor)