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Topic: Forklift Ergonomics 

rich hirsh  Posted: Jan 12, 2005 03:40 PM Post Reply (Msg. 1 of 5)

I have a problem which is applicable anywhere folks spend a lot of time on a fork lift truck.

We just had an injury yesterday where a fork truck driver, who hauls pallets into the plant

from the delivery trucks and distributes them to different areas inside the plant, hit a lump

of ice that jarred his lower back and caused a strain. I believe this is a cumulative trama

issue in that he is a 31 year veteran who has spent most of his career on a fork truck. The

lump of ice was just the end result of driving a truck that does not have suspension (forklift

is made that way. there is a seat suspension and we do buy pads as needed for drivers) and

he could have easily hit an uneven floor or crack or other potential obstacle that could have

caused this injury. I would like to measure the force the drivers are exposed to during the

operation of their trucks. I view this as an industrial hygiene test in that chuck holes,

running into and out of trucks, up ramps, etc result in a form of cumulative trauma to the

driver. I want to determine these exposures so I can address the bigger picture of 

eliminating these excess force exposures. Can anyone suggest a method(s) of determining

this exposure like a pressure pad, or force/vibration monitor attached to the truck, etc?

Your help is much appreciated. Thanks.

Rich

DaveMac  Posted: Jan 12, 2005 09:40 PM Post Reply (Msg. 2 of 5)

Rich

You might want to use the current version of the International Standard for whole body

vibration (ISO 2631) to assess the driver's typical vibration exposure.

Regards,

David.

Reference

International Organization for Standards, (current edition), ISO 2631, “Guide for the

Evaluation of Exposure to Whole-Body Vibration”.

Rick

Goggins Posted: Jan 13, 2005 01:17 PM Post Reply (Msg. 3 of 5)

Years ago I evaluated whole body vibration with forklift operators on a loading dock.

Basically you use a vibration meter with a three-axis sensor that the workers sit on (it's like

a hard whoopie cushion, very uncomfortable). I'm sorry that I can't find the report, but I

did find that going over even smaller bumps such as dock plates and thresholds resulted in

z-axis shocks that exceeded the ISO whole body vibration standards. These bumps were, I

would imagine, a lot smaller than that lump of ice in your case. You still might consider

having a vibration study done to see if the levels under normal operating conditions are

enough to risk injury or result in fatigue.

Typical recommendations are to limit speed on the forklifts, and to smooth out transitions

and fill in any significant floor cracks.

Vedder  Posted: Jan 14, 2005 12:55 AM Post Reply (Msg. 4 of 5)

Hi Rich,

10 years ago I did a study on seat vibration of operators of wheel loaders and tracked

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excavators, using three different approaches. I measured the vibration using a seat

cushion.

1) I measured the real exposition during entire work shifts.

2) To be able to compare different vehicles I set up a standard course for the drivers to go

through at a specified speed.

3) I measured the vibration levels on the seat and at the seat base to evaluate the damping

capacity of the seat. The damping values were around 1.0 for normal operation which

means no damping at all; and up to 1.4 (amplification instead of damping!) for the test

course which was gone through at a higher speed than normal. We found out that the seatresonant frequency was identical to the Eigenfrequency of the wheel loaders.

So my recommendation would be to measure the real vibration and the damping of the

seats. And if needed, re-adjust the seats or get seats with better damping.

Also, body posture seems to be an important factor. Check if your drivers can adopt a

comfortable posture (most fork lift truck provide not enough space for that); both, for

driving forward and backwards. Another factor could be the visual field during operation.

How often does the driver have to lean sideways or adopt other uncomfortable positions to

be able to see what he needs to see (and how often does he use "experience" where he

cannot see anything...)? Modern fork lift trucks with larger cabins and smaller motor

housings often provide better visual conditions resulting in less stressful body postures.

Plus, of course, the reduced accident risk.

JohnMc  Posted: Jan 20, 2005 02:01 AM Post Reply (Msg. 5 of 5)

Rich,

I worked on a similar ergonomic concern in 1999. After our investigations, we concluded

that the root cause was that when our Forklifts are in constant use the seat systems lose

their effectiveness after 2 - 3 years of 24/5 work. Some of our trucks were seven years old

with original seats.

When we replaced the seat units with the manufacturers replacement parts after three

years use, the concern went away and has not returned.

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