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The Step/Skirt Performance Index was defined under a
multi-year study with the purpose of establishing measurable parameters that
affect the potential for entrapments on escalators. Entrapments in this case
include finger/hand, calf, and shoes trapped between the escalator step and
skirt. Based on empirical data, it was determined that the gap between the
step and skirt, and the coefficient of friction (skirt panel and skin/shoes)
were quantities that had a significant affect.
Step/Skirt Performance Index
The step/skirt performance index is calculated from the
measurement of two quantities and is defined only for the inclined section
of the escalator. The first quantity is the loaded gap(Lg). This is the
distance between the edge of the step and skirt, while the step is ‘pushed
away’ from the skirt using a force of approximately 110 N (25 lbs). The
second quantity measured is the coefficient of sliding friction (µ) between
the skirt panel and a standard polycarbonate test sample (PMT supplied). The
Index is defined as:
Step/Skirt Performance Index = ey/(ey + 1)
Where: y = -3.77 + 2.37(µ) + 0.37 (Lg)
e = 2.7183
(Lg in mm)
This is an example of an Index Measurement Time History
(EVA Software). The values of loaded gap (upper graph) and coefficient of
friction (middle graph) are used, at each point in time, to calculate the
Step/Skirt Performance Index (lower graph) using the formula above.
Measurements are made on each side of two representative steps (a total of 4
measurements). |
