Reaching for Standardization

Guy Ramsey

March 9, 2006 — How do you determine the maximum vertical reach on an aerial work platform (AWP)? At least in North America, the commonly accepted practice is to take the platform height and add 6 feet. European standards allow for an additional 2 meters (or nearly 6 1/2 feet). So, for example, if the platform height of an aerial lift is 60 feet then the working height is 66 feet. The other day the marketing director of one of the larger aerial work platform OEMs asked me what, if any, industry standard existed for maximum horizontal reach. What a great question, I thought to myself. I have often noticed that there appears to be a variation between the published specification and what the range of motion chart shows.

 

Typically “outreach” or horizontal reach is measured from the machine's centerline of rotation to the outer edge of its work platform. When OEMs state their maximum horizontal outreach dimension in product literature, are they actually taking into consideration the extra distance gained by reaching over the guardrail? My cursory investigation leads me to believe the answer is, “not always.”

 

If you look at each of the manufacturer's specifications, the written specification is often the exact distance from centerline to the edge of the platform, while the range of motion often shows a different story. Sometimes the work envelope is shown to be some distance beyond the platform's edge. This compels me to ask three questions. 1) To remain consistent with the maximum vertical reach, should a safe over-the-side reach dimension be incorporated in the specification? I believe it should. 2) Should the published specification for maximum horizontal reach match the range of motion diagram? Again, to avoid confusion, I believe it should. I see no reason or benefit from them being different. 3) If you do have a standard addition specification for an over-the-guardrail dimension, what should it be?

 

If you're standing with a top guardrail just above your stomach (say 40 to 43 inches), how far can you safely reach over the guardrail? 12 inches? This seems a little conservative. How about 36 inches? This would probably work for Yoa Ming. I decided to get my tape measurer and a plumb bob out to set up a simple “scientific” test. Leaning up against a 40-inch countertop, I held the end of the string comfortably out in front of me and dropped the plumb. Measuring out from the edge of the counter I noted that the plumb rested at about 24 inches. I am above average in height and have a couple inches reach on most people. I imagine an average individual could comfortably and safely reach 20 inches outside the platforms top rail.

 

If you can work 20 inches over the side of a guardrail, is it fair for an OEM to publish a machine's horizontal reach from the centerline of rotation to a point 20 inches past the leading edge of the guard railing? From my perspective, I can't see any reason not to. It seems a prudent representation of what is a comfortable work position without mitigating the safety of the guardrail system. It also holds consistent with the practice of adding distance (6 feet or 2 meters) to the platform height of a machine.

 

There are many other aspects of reach that should be addressed, many of which we'll be discussing in future editions of Lift and Access magazine. As always, we value your comments and input as we try to come to some consensus on industry issues. Please write me at gramsey@liftandaccess.com with your views on this subject.