Cable guides that do not require manual manipulation to pass them are preferable. Weather-resistant, synthetic cables that have long lifetimes in corrosive atmospheres are available. They offer the additional advantage of radio-frequency transparency for antennas. Synthetic cables must be protected from wind abrasion, with the structure by suitable clearance spacing.
Telecommunications tower cable-type fall protection systems and Z-bracket rungs which may be less than 3/4 inches diameter and less than 16 inches width, must meet test requirements.
A very important principle of climbing, using vertical cable-type fall arrestors is to never hold the cable for any reason. The reason for this is to prevent the transfer of weight through the handhold above the sleeve, and thereby stop or limit the gripping arrest of the line by the sleeve itself.
See “Introduction to Fall Protection, 4th Edition” page 322.
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Three Point climbing without fall protection e.g. (movement at height with two hands & one foot alternating with two feet & one hand) can be better analyzed as follows:
1. Three Point Stance: American football term readiness to start play; FMCSA/DOT access points for truckers to/from the cab with at least two digits & no cutting of the finger at the second digit.
2. Three Point Contact: any point of body contact plus two feet position to climb and work balanced hands-free (no performance based definition).
3. Three Point Control: Hand or hands on a round rung or horizontal grab bar and a horizontal round or flat level for foot or feet. Ideal round grab bar or rung for optimal handhold performance is 1″ diameter based on a handhold coupling study of 36 subjects by Justin Young, Kettering University, Michigan, link: http://hdl.handle.net/2027.42/84452 .
Vertical handholds slide during a fall. Handhold shapes like angle iron fail to arrest dynamic falls both vertically and horizontally. Bottom line is that dynamic force on the hands arresting body weight is surprisingly large, and the 1″ diameter horizontal bar is the best shot we have for safe performance on structures at height. Designers need to understand this human limitation when designing tower structures, and tower climbers need to understand no free-climbing at any time.
Examples of climbing are shown.
Note: please wait a few seconds as sketches show movement.
THREE POINT CONTROL-GRABSAFE FOR PORTABLE LADDER
THREE POINT CONTROL- HATCHGRIP FOR ROOF HATCH
THREE POINT CONTROL-GRABSAFE FOR FIXED LADDER