Self-Established Ergonomic Standards

In my experience, it's uncommon to see much effort toward in-house standards for new equipment. Some companies understand the need, but there are plenty that focus on committees that mainly redesign existing equipment and answer employee complaints.

Attempting to retrofit newly installed equipment is doing it the hard way. No engineer or plant manager wants to hear that equipment that has been carefully designed, budgeted for, built and installed now needs revisions due to lack of advance specifications.

It’s far less expensive to design in ergo features at the start of a project than to retrofit them after completion. It also makes use of our in-house talent to give the experienced, educated designers a chance to build-in ergonomics instead of asking an ergonomics committee to try to find and correct after the fact.

Some states have existing ergonomics regulations, so that is a good place to start. In the absence of governmental instructions, in-house standards can be developed based on available ergonomics research.

Humantech has compiled quite a lot of excellent information in its “Handbook of Ergonomic Design Guidelines.” It’s available along with several other publications at http://www.humantech.com. Federal OSHA's 1910.900 Table W-1 assembled a wide range of ergonomic research into a single concise table. The standard is long gone now and won't be coming back, but the table still has its uses.

Here is an example of a simple approach to in-house standards. Knowing many ergonomics programs depend on employee involvement to build employee buy-in and improve results over the old “top-down” approach, we would choose a simplified set of standards rather than a thick volume for their accessibility.

Postures:

1. Limit repetitive reaching to less than 12 inches from front of rib cage. Heavier workers will require a shorter distance – 8 inches to 10 inches – from foremost obstruction to hand destinations.

2. No lifting to load or unload pallets, or repetitive reaching for controls, with hands below knees or above shoulders. For optimum lifting and repetitive reaching at elbow height, keep distance at 35 inches to 45 inches.

3. When assembling parts or loading fixtures, work at elbow height between 35 inches and 45 inches. (The iscrepancy with No. 2 is related to percentage of cycle time spent in posture).

4. Keep elbows at sides while working, with work height of fingers same as elbow height.

5. Keep parts and fixture all on the same plane.

6. Hand tools: Handles should be 1 inch to 1 ¼ inches in diameter and 5 inches to 6 inches long, with rounded ends and made from lightweight materials where feasible (aluminum, polycarbonate, etc., usually can be used for handles with steel inserts for tool shafts or tips).

7. Position initiation switches at a height – elbow height is optimal – and angle that allow straight wrists and fingers when using – optimum angle adjustable.

8. Operator touch screens and monitors should be placed at approximately 55 inches to 65 inches from floor level – optimum height and angle adjustable.

Forces (should be as minimal as practical):

9. No manual handling of drums other than empties.

10. No hand lifting over 30 pounds; simple lifts only.

11. Limit initial forces to less than 40 pounds and sustained push/pull forces to less than 20 pounds when moving pallet jacks or carts.

12. Assembly push force should be limited to no more than 2 pounds.

13. Pinch grip should be less than 2 pounds and briefcase grip less than 10 pounds for any grips lasting more than 10 seconds.

14. Foot pedal force should be less than 10 pounds.

15. Springs should be set by machine, not by hand.

16. Any in-process container lifted by hand is better with handles.

Repetition:

17. Initiation switches should use optical sensors rather than spring-loaded buttons.

18. Initiation switches should be mounted on individual pods if necessary to minimize obstruction of common mounting box.

19. Engineer out flipping motions/dishrag hand motions where feasible.

20. Suspend tools close to point of use, position them at angle of use, control tool torque by suspension and strive for minimum force required to move to point of use.

21. Use tools and equipment that expose the hands of operators to only minimal vibration.

22. Remember that primary operator protection light curtains, muted during non-hazardous portions of cycle with initiation by a single hand or foot switch, “trip” better than “controls” where controls are not required for protection.

In-house specs can serve in engineering new processes, new installations of old processes and new equipment purchases. Consider the value of in-house standards to your ergonomics process.

William H. Kincaid, P.E., CSP, is a vice president and loss control consultant with Lockton Companies, LLC.