Petzl Tandem Pulley

The Petzl Tandem pulley has two sheaves in line so it rides a tensioned rope smoothly, which is why it shows up on speedlines and tyrolean traverses. Among Petzl pulleys, it is the one built for moving along a line rather than redirecting one.

Using a tandem pulley on a speedline

On a speedline, brush hung from a single pulley tends to tip and drag. A tandem pulley spreads the load along two sheaves, so it tracks straight and runs fast. Clip the brush to the pulley with a sling and locking carabiner and let it go.

Line angle and tension decide how fast loads arrive. Have a plan for stopping them at the bottom.

The side plates open so you can install it on the line without untying, which saves time when each load needs its own pulley. Many crews keep several on the line so the climber always has one ready while the ground crew collects the last load.

Stop the brush at the bottom with a soft landing, such as a brush pile, or by having the low end tied off on a friction device so it can be eased.

Inspection

Check that both sheaves turn freely, side plates are not bent and the axles are tight. Retire after damage or a severe shock load. Speedlines are rigging, not life support, unless the whole system is designed and rated for that use; follow Petzl's instructions and train to ANSI Z133.

Keep the pulley clean of sap and grit, which slows the sheaves and wears the rope faster.