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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