What is the center of the playground grasping device?

What is the center of the playground grasping device?

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Playgrounds can be a blast and horizontal (monkey bars) ladders are a lot of fun too.  Unfortunately, a horizontal ladder installed above 84 inches can quickly lead to broken arms and other injuries, especially if those ladders go unsupervised.  As any good risk manager would tell you, get out there and measure those monkey bars.  And that is where the controversy begins.

What is the center?

The two standards to measure by are ASTM and CPSC.  Generally they both say the same thing, which is to measure from the center of the grasping device to the surfacing below; however, ASTM does this in a very poor manner.  ASTM specifies how to measure in the sentence regarding 2-5 year old measurements and leaves it out of the 5-12 year old measurement.  Therefore, we must go to CPSC Handbook 325 to see the intention of the measurement and determine that it applies to both age groups, which it does.  The CPSC Handbook 325 clearly denotes that the measurement process remains the same for both age groups, something ASTM should take a hint from.

When reviewing previous playground inspection reports, I often see where an inspector interpreted that the maximum height for 5-12 age group was the very top of the horizontal ladder’s grasping device, not the center of the grasping device based on their interpretation of ASTM 1487.  So, now we know we must measure to the center of the grasping device.

ASTM 1487

8.3.3

8.3.3 The maximum height of upper body devices for use by
2 through 5-year-olds shall be no greater than 60 in. (1524
mm), measured from the center of the grasping device to the
top of the protective surfacing below. The maximum height of
upper body devices for use by 5 through 12-year-olds shall be
no greater than 84 in. (2130 mm). Upper body equipment
intended for users in wheelchairs shall have grasping devices
no greater than 54 in. (1370 mm) above the accessible surface

CPSC Handbook 325

5.2.3.4

The maximum height of a horizontal ladder (i.e., measured
from the center of the grasping device to the top of
the protective surfacing below) should be:
– Preschool-age (4 and 5 years): no more than 60 inches.
– School-age: no more than 84 inches.

 

What is a grasping device?

Once we understand that we must measure to the center of the grasping device, then we really need to know what a grasping device is. That requires that we understand the intention of the manufacturer and the design of the device itself. If the manufacturer did not intend for the upper portion of a triangle to be part of the grasping device, then should we measure it?  Probably not, but it really depends on the style. There are many grasping device styles these days and this leads to the confusion. Let’s take a look.

The straight bar

This is your traditional horizontal ladder.  A single rung across two support bars.  The rungs are typically 3/4 of an inch in diameter so, measuring to the center of the rung/grasping device leaves 3/8 of a inch on either side – not a big deal.  But what happens when we create a shape that has a 13 or 14 inch span?

Triangles, circles, wheels and U-shapes

In recent years new horizontal ladder (upper body equipment) styles have flooded the market.  And these devices are causing much of the confusion about where to measure.  Going back to intention, let’s take a look at triangle shape.  The manufacturer didn’t intend for the upper legs to be used as a grasping rung; however, children will use playground equipment in all types of manners that were unintended.  So, at this point we have to look at design and this is where the manufacturer’s typically fail at separating intention from design.

Again, the rung is typically 3/4 of an inch in diameter and this same diameter continues up the upper legs of the triangle or in the case of a spiral or U-shape, the entire length of the device.  If the intention was to have the user only utilize the lower base/rung, then the upper legs would change diameter to indicate sensory touch differences to the user.  However, almost all of the triangles, circles, wheels and U-shapes that we see today do not change diameter meaning that the entire triangles, circles, wheels and U-shapes must be considered part of the grasping device.

To measure these triangles, circles, wheels and U-shapes, you need to measure to the center of the overall device.  This can be done by measuring to the bottom of the base/rung (b) and then to the highest part of the upper leg (u), then find the center by dividing the difference between in half and adding that half to (b).  Below are some examples of where to measure the center of the device.

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