A worker is asked to move 30 boxes from a desk onto a shelf within 3 minutes (assume there is enough space and no other lifting work within 8 hours). The shelf height is 55 inches, and the desk height is 30 inches. The initial horizontal distance from the box to the body is 7 inches. Assume that all the boxes are in the same size (8 inches edge, cube), each weigh 20 lb., and have well designed handles. Is there any lifting risk according NIOSH lifting guide

LI = Lifting Index = 0.71

No lifting risk is involved

Explanation:

NIOSH Lifting Index

LI = Load Weight / Recommended Weight Limit

LI = L / RWL ... Eq (A)

NIOSH Recommended Weight Limit equation is following,

RWL = LC * HM * VM * DM * AM * FM * CM ... Eq (B)

Where,

LC = Load constant

HM = Horizontal multiplier

VM = Vertical multiplier

DM = Distance multiplier

AM = Asymmetric multiplier

FM = Frequency multiplier

CM = Coupling multiplier

Given data

V = 30 + (8/2) = 34 in

H = 7 in

D = 55 - 30 = 25 in

A = 0

F = 10 boxes/min

C = 1 = Good coupling

According to NIOSH lifting guide

LC = 51 lb

HM = 10/H

VM = 1 - {0.0075 * (v-30) }

DM = 0.82 + (1.8/D)

AM = 1 - (0.0032*A)

FM = 0.45 (Table 5 from NIOSH lifting guide)

CM = 1 (Table 7 from NIOSH lifting guide)

Solution:

RWL = 51 * (10/7) * [1-{0.0075 (34-30) }] * (0.82 + 1.8/25) * (1-0.0032*0) * 0.45 * 1

RWL = 51 * (10/7) * 0.97 * 0.892 * 1 * 0.45 * 1

RWL = 28.37 lb

Using equation A

LI = L / RWL

LI = 20 / 28.37

LI = 0.71

According to NIOSH lifting guide LI < = 1

So No lifting risk is involved