Tech Tip: Safe Handling of the Petzl Shunt Backup Device

There are many backup devices on the market. Our testing here at Ropeworks has given us a strong preference for the Petzl Shunt. It is the most widely-used backup device in the rope access industry throughout the world. This article will refresh your memory about good handling practices, and also try to answer “why” we follow these guidelines.

As with any item of life support equipment, technicians require training on the Shunt. In this Tech Tip article we’ll cover some of the most important handling practices that you will need to know to use it as your backup device. Please remember that an article is only an aid, and that we strongly recommend that every technician receive personal instruction and refresher training at regular intervals.

Rule #1: Don’t handle the body of the Shunt! When moving the Shunt up or down on the rope, it’s vitally important not to handle the body. Move it upward by lifting the carabiner or the lanyard, and downward only by tugging on the tow string. If you were to fall while holding the body of the shunt, it could be held open by your hand’s reflexive clutching motion and fail to grip the rope!

Don’t grab the backup rope above the Shunt, for the same reason. As you fall, your hand could push the Shunt down the rope from above and keep it from working. Don’t tie a loop in the Shunt string, or wrap it around your finger. In the event of a fall, the tow string must be released in order for the Shunt to grab. If the string is tied to your hand, the Shunt could be pulled down with you. With smaller cords (2mm) tying a small overhand knot (as shown above) at the end of the tow string may help you keep control while still allowing the string to slip free of your hand.

Don’t place your backup device close above a knot or an edge. A Shunt requires some “running room” in order to absorb the energy of a fall. The higher it is above a knot or edge the more energy it can dissipate by slipping. This will minimize the shock to it and you if the main line fails. Chest high is good, head high is better, and overhead is the best position of all. It’s always important, but during a pick-off rescue the Shunt’s position is even more critical. In order to catch the extra mass of a two-person shock load the Shunt must be kept nearly as high as its lanyard will allow at all times during the rescue.

The Shunt performs differently with different ropes. We tested the maximum impact force on variety of ropes, and compared the Shunt against several other devices. To read the details and conclusions of our testers, visit the Ropeworks web site’s Tech Center