The aim of this post is to explain how anti-pendulum anchors are used to limit swing fall hazard – a hidden threat that exists at the corners and the protruding parts of a roof.
With a horizontal lifeline system, a lifeline (also known as an anchorage line) is placed in the middle of a roof. Users are anchored to this lifeline with a lanyard which is attached to the safety harness that they wear.
No swing fall hazard
A user can safely approach a straight roof edge that is parallel to the lifeline, provided that the distance between the user and the anchorage point (i.e. the length of the lanyard) remains the same. In this case, there is no swing fall hazard. *1
Swing fall hazard at protruding parts of the roof
However, to enter a protruding part of the roof, the distance between the user and the anchorage point (and thus the length of a user’s lanyard) will increase. If a user then falls off the side of the protruding part, the lengthy lanyard can cause a big swing – which in turn will cause a user to hit the parallel wall (or another object that stands in the way) at a great speed. *2
Swing fall hazard at roof corners
When a user wants to approach a roof edge that is perpendicular to the direction of the lifeline (the front side of the roof pictured), then the length of a user’s lanyard will increase as he gets closer to a corner of the roof. If that user falls off the front side, the lengthy lanyard will also cause a big swing, back and forth along the front wall. *3
In some cases, the length of the lanyard can even cause a user to hit the ground.
1: No swing fall hazard. 2: Swing fall hazard at protruding parts of the roof. 3: Swing fall hazard at roof corners.
Anti-pendulum anchors are anchor points which are placed closed to the roof edge, in areas where swing fall hazard exists. They are used in conjunction with the lifeline system – users always remain anchored to the horizontal lifeline at the middle of the roof, but they loop their lanyard through a safety hook which they attach to the anti-pendulum anchor.
Users must always connect their lanyard to the anti-pendulum anchor BEFORE they approach the roof edge in an area where swing fall hazard exists:
In this way, the size of the swing that will occur when a user falls over the edge is limited by the shorter distance between the user and the anti-pendulum anchor. *4
Anti-pendulum anchors are placed no more than 2 meters (6.5 feet) away from the roof edge. Limiting the size of the swing restricts the fall height in case of a fall. This also decreases the speed of the swing (and thus the impact of the hit if a user hits an object during the swing fall).
A horizontal lifeline track could also be placed alongside every edge of the roof, so that the lifeline is always parallel to the roof edge. However, this would only eliminate swing fall hazard if the lifeline is no more than 2 meters (6.5 feet) away from the roof corner.
Some lifeline systems are designed for simultaneous use by multiple users.
If you would like more information about our fall protection solutions, request our fall protection brochure. For advice about the most suitable fall protection solution for your building or project, it’s best to contact us directly.
Useful article for all Civil Engineers