What is Pendulum Distance and Why Does It Matter When Setting Up Fall Protection Equipment?

Per OSHA standards (1926.501), solar construction staff installing systems who are exposed to fall distances of 6 or more feet must be protected from falls by using one of the following methods: personal fall arrest systems, guardrail systems, or safety net systems. On residential solar installations, personal fall arrest systems are the most commonly used. Understanding how to properly install, utilize, and maintain these systems should be one of the first things installers learn when being onboarded. 

In this short video excerpt from Solar Construction Safety, HeatSpring instructor Tripper Gawan talks about pendulum distance and why it’s important to consider every time your team is setting up anchors on a residential job site. Tune into the video or read the transcript below. To dive much deeper into fall protection and other key safety practices, enroll your team in Solar Construction Safety. 

Now we’re going to do fall protection – deeper dive.   First, we’re going to start off with pendulum distance. As you can see with this diagram, pendulum distance is to make sure – just like a pendulum – that the swing that takes place based on the anchor point is not so great that you could injure yourself further than the fall scenario is already dictating.

In this case, this guy’s pendulum distance, he put his primary anchor too close to this wall so that when he fell, he swung off and landed right into the wall. This pendulum angle is supposed to be no greater than 45 degrees. Once you pass 45 degrees/46 degrees, the opportunity for your deceleration distance and your free fall distance to exceed their limitation and for you to impact the ground is greatly increased. 

So your pendulum distance is the distance that’s required for you to have a fall-related event, come off the roof, be in a fall arrest situation, have deceleration occur, have yourself be at the low end of that deceleration or pendulum, and not be touching the ground. That’s for pendulum  deceleration device.

Now that is this cute little device right here on this person’s back or this person’s back here, understand a couple of key considerations:

Number one, the anchor point is crucial. We talked about anchor installation, following manufacturer specifications and protocols, doing multiple anchors, making sure we have transitionary anchors, whatever it is. Install those anchors correctly, harness up, hook up to that anchor correctly. Make sure all your equipment is in good use. 

Make sure your deceleration device is intact and does not have any marring, scarring, scratches, or other nicks that would indicate its inability to act appropriately. That deceleration device is approximately 6 feet worth of wrapped up material that slowly releases to slow down your acceleration to ground, which is 9/8 meters per second. It’s the gravitational pull of Earth.  So you don’t have a sheer impact with that, it slows down your impact, so it’s a little more like a bungee cord than a rope snap.  That’ll help you from having secondary injuries due to that fall as well.  

With the deceleration devices, that deceleration distance that I just mentioned, which is approximately six feet.