5.2
Calculating Minimum Required Fall Clearance
5.2.1
FT-R in Overhead, Non-Leading Edge Anchorage Application
The FT-R may be used may be used as a standard SRD in an overhead
condition, in which the SRD is installed anywhere in the allowable attachment
area, which ranges from directly above the user to level with the FBH D-ring, as
shown in Figure 4.
Z- Minimum Required
The overhead condition minimum required fall clearance (MRFC) is
Fall Clearance From
calculated using four metrics, measured from the walking-working surface:
Working Surface
SRD Deceleration Distance, D-Ring Shift and Harness Stretch [1 ft (0.3m)],
Safety Factor [1.5 ft (0.5m)], and Swing Fall. Chart 1 below is calculated using
the performance data of the SRD and includes all four metrics listed previously
to determine the MRFC.
Lateral Offset Distance (Y)
Chart 1
Overhead
0 ft
(0 m)
60 ft
6.0
(18.3 m)
(1.9)
55 ft
6.0
(16.8 m)
(1.9)
50 ft
6.0
(15.3 m)
(1.9)
45 ft
6.0
(13.8 m)
(1.9)
40 ft
6.0
(12.2 m)
(1.9)
35 ft
6.0
(10.7 m)
(1.9)
30 ft
6.0
(9.2 m)
(1.9)
25 ft
6.0
(7.7 m)
(1.9)
20 ft
6.0
(6.1 m)
(1.9)
15 ft
6.0
(4.6 m)
(1.9)
10 ft
6.0
(3.1 m)
(1.9)
5 ft
6.0
(1.6 m)
(1.9)
0 ft
6.0
(0 m)
(1.9)
2 foot (0.6 m) increments along the Y-Axis represent the Lateral
Offset Distance the user is working away from being directly
Example:
If the user needs to work 10 feet (3.1 m) away from directly under the SRD, the SRD needs to be anchored at least 15 feet (4.6 m) above
the user's Dorsal D-Ring. Minimum required fall clearance is 9.5 feet (2.9 m) at maximum allowable swing fall.
Example:
If the only suitable Anchorage for the SRD is at D-Ring height [0.0 feet (0.0 m)] above the user's Dorsal D-Ring, the maximum allowable
work zone is 4 feet (1.3 m) away from the SRD. Minimum required fall clearance is 10.0 feet (3.1m) at maximum allowable swing fall.
Key to Work Zone Areas:
MSRD20 Rev D
2 ft
4 ft
6 ft
(0.7 m)
(1.3 m)
(1.9 m)
(2.5 m)
6.5
6.5
6.5
(1.9)
(1.9)
(2.0)
(2.0)
6.5
6.5
6.5
(1.9)
(1.9)
(2.0)
(2.1)
6.5
6.5
6.5
(1.9)
(1.9)
(2.0)
(2.1)
6.5
6.5
6.5
(1.9)
(1.9)
(2.0)
(2.1)
6.5
6.5
6.5
(1.9)
(1.9)
(2.0)
(2.1)
6.5
6.5
7.0
(1.9)
(1.9)
(2.0)
(2.2)
6.5
6.5
7.0
(1.9)
(2.0)
(2.1)
(2.2)
6.5
6.5
7.0
(1.9)
(2.0)
(2.1)
(2.3)
6.5
6.5
7.0
(1.9)
(2.0)
(2.1)
(2.3)
6.5
7.0
7.5
(1.9)
(2.0)
(2.2)
(2.5)
6.5
7.0
8.0
(1.9)
(2.1)
(2.4)
(2.7)
6.5
7.5
9.0
10.5
(1.9)
(2.3)
(2.7)
(3.1)
8.0
10.0
12.0
14.0
(2.5)
(3.1)
(3.7)
(4.3)
Using Chart 1 to Calculate Minimum Required Fall Clearance for the FT-R
under the SRD
= Allowable Use Area
WORKING IN THIS AREA
20.5
28.0
8 ft
10 ft
12 ft
14 ft
(3.1 m)
(3.7 m)
(4.3 m)
7.0
7.0
7.5
8.0
(2.1)
(2.2)
(2.4)
7.0
7.0
7.5
8.0
(2.2)
(2.3)
(2.4)
7.0
7.0
7.5
8.0
(2.2)
(2.3)
(2.5)
7.0
7.5
8.0
8.5
(2.2)
(2.4)
(2.5)
7.0
7.5
8.0
8.5
(2.3)
(2.4)
(2.6)
7.0
7.5
8.0
9.0
(2.3)
(2.5)
(2.7)
7.5
8.0
8.5
9.5
(2.4)
(2.6)
(2.8)
7.5
8.0
9.0
10.0
(2.5)
(2.7)
(3.0)
8.0
8.5
9.5
10.5
(2.6)
(2.9)
(3.2)
8.0
9.5
10.5
12.0
(2.9)
(3.2)
(3.6)
9.0
10.5
12.0
13.5
(3.1)
(3.6)
(4.1)
12.5
14.0
16.0
(3.6)
(4.1)
(4.6)
16.0
18.0
20.0
(4.9)
(5.5)
(6.1)
5 foot (1.5 m) increments up the X-Axis represent the
SRD Anchorage Height above the user's Dorsal D-Ring
= Not Allowed Use Area
MAY RESULT IN SERIOUS INJURY OR DEATH
021722
Figure 4 - MRFC Overhead Anchorage
X-SRD Anchorage Height
Above Dorsal D-ring
Y- Lateral
Z- Minimum Required
O set Distance
Fall Clearance From
Working Surface
16 ft
18 ft
20 ft
(4.9 m)
(5.5 m)
(6.1 m)
8.5
9.0
9.5
(2.5)
(2.7)
(2.9)
8.5
9.0
10.0
(2.6)
(2.8)
(3.0)
8.5
9.5
10.0
(2.6)
(2.8)
(3.1)
9.0
9.5
10.5
(2.7)
(2.9)
(3.2)
9.5
10.0
11.0
(2.8)
(3.1)
(3.3)
9.5
10.5
11.5
(2.9)
(3.2)
(3.5)
10.0
11.0
12.5
(3.1)
(3.4)
(3.7)
11.0
12.0
13.5
(3.3)
(3.6)
(4.0)
12.0
13.0
14.5
(3.6)
(4.0)
(4.4)
13.0
14.5
16.0
(4.0)
(4.4)
(4.9)
15.0
17.0
18.5
(4.6)
(5.1)
(5.6)
18.0
20.0
22.0
(5.5)
(6.0)
(6.6)
22.0
24.0
26.0
(6.8)
(7.4)
(8.0)
22 ft
24 ft
(6.8 m)
(7.4 m)
10.0
11.0
(3.1)
(3.3)
10.5
11.5
(3.2)
(3.4)
11.0
11.5
(3.3)
(3.5)
11.5
12.0
(3.4)
(3.7)
12.0
13.0
(3.6)
(3.9)
12.5
13.5
(3.8)
(4.1)
13.5
14.5
(4.1)
(4.4)
14.5
16.0
(4.4)
(4.8)
16.0
17.5
(4.8)
(5.3)
18.0
19.5
(5.4)
(5.9)
20.5
22.0
(6.2)
(6.8)
24.0
26.0
(7.2)
(7.8)
28.0
30.0
(8.6)
(9.2)
9