Fall Arrest Safety Cables
Fall Arrest Safety Cables
(OP)
I am evaluating existing fall arrest safety cables running along walkway and attached to W4x13 posts spaced at 20ft. The worst case would be if a force is applied on cable at middle between cable posts. Correct? How would you calculate tension force in the cable? Does force of 5,000 lbs need to be used? Any advice would be appreciated.
iv
iv






RE: Fall Arrest Safety Cables
Quando Omni Flunkus Moritati
RE: Fall Arrest Safety Cables
Of course this is how the HLL suppliers I've worked with designed their system, contact the system's original manufacturer for technical support.
wadavis
E.I.T.
RE: Fall Arrest Safety Cables
assume a 500lb load, each half of the cable reacts 250lbs
assume a span of 20', so each half cable span is 10'
the cable makes an angle to the straight line between the anchors of asin(250/5000) = 0.05rad = 3deg
cable length = 10'/cos(0.05) = 10.0125', slack = 0.15" !!
with 2" of slack, then half the cable is 121" long
and the deflected angle is acos(120/121) = 0.13rad = 7deg
and a 5000 lbs cable tension can support a load of 2*5000*sin(0.13) = 1283 lbs
it's a slow day !
Quando Omni Flunkus Moritati
RE: Fall Arrest Safety Cables
The 5,000# force does apply if you do not use energy dissipating devices or devices that limit the fall distance and kinetic energy being built up. Energy dissipating devices are shock absorbing lanyards. Self-retracting lanyards lock the worker in before they can fall a great distance. Both will limit what is called a max. arresting force. I have seen this force as low as 900#. Using the OSHA S.F. of 2, that would bring the load to 1800#.
Do an internet search for USS Wire Rope Engineering Handbook. It has calculations in it for exactly what you are looking for. Someone on here might have it and posted it. You should review the handbook to make sure you understand the theory of cable behavior. One last thing: if the cable is large in diameter and spanning a long distance, you should investigate the sag of the cable from self-weight and if outdoors, from ice on it.
CJC
RE: Fall Arrest Safety Cables
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I only mention Miller since i use them when i design these applications
RE: Fall Arrest Safety Cables
RE: Fall Arrest Safety Cables
Bear in mind the max. arresting force I mentioned is the vertical "fall" load applied to the cable, not the tension in the cable. They are very different. IFRs is correct in that the max. arresting force can be reduced only if the system is designed by a qualified PE.
CJC
RE: Fall Arrest Safety Cables
RE: Fall Arrest Safety Cables
RE: Fall Arrest Safety Cables
iv
RE: Fall Arrest Safety Cables