This question will use the body dimensions derived from Table 5-1. The difference between shoulder height (#3) and knuckle height (#5) for a 95th percentile male is 60 -31.7 = 28.3 inches. At a 90° abduction, a 20 pound weight creates a torque of 28.3/12 × 20 = 47.1 foot-pounds at the shoulder. Note that this value is less than the 95th percentile male shoulder vertical abduction capability of 75 foot-pounds from Table 4-1.
NIOSH evaluation (Only one calculation is made for a combined origin and destination because the inspector is only lifting the product slightly. An assumption is made of an 8-hour lifting, with good coupling and no twisting):
|RWLorigin||= 51||(10/H) (1 – .0075|V-30|) (.82 + 1.8/D) (1 – .0032A) (FM) (CM)|
|= 51||(10/20) (1 – .0075|40-30|) (1) (1) (.35) (1) = 51(.5)(.925)(.35) = 8.26|
|LI||= 20/8.26 = 2.42 which is unacceptable|
It is a must to reduce the frequency to one lift in every five minutes (with FM=.85) before RWL even approaches 20 pounds. It is therefore important to make a physical redesign of the workstation.
Energy expenditure considerations:
R = (W – 5.33)/(W – 1.33) = (6 – 5.33)/(6 – 1.33) = .143
The fact that energy expenditure of 6 kcal/min is above 5.33 kcal/min, approximately 1.14 hours of rest are required for every 8-hour shift.
An employee that is working too hard is not receiving enough rest according to the heart rate guidelines.
The Brouha’s guidelines recommend that the difference between the first and the third minutes should be at least 20 beats. In the current case the difference is 110-95=15 beats which is too little. It therefore means that the employees are not fit enough and their heart rate is not recovering as fast as it should