How to use a prusik-minding pulley (PMP)

Pulleys with side plates designed to accommodate prusik brakes are referred to as "Prusik Minding Pulleys" (PMPs). These pulleys are designed with tolerances that allow appropriately-sized ropes to run through them, but they cleanly block the passage of a prusik hitch.

Source: This article was Adapted from Vertical Academy, by Tom Briggs, Copyright © 2013. All Rights Reserved. Excerpted with expressed written permission. To purchase your copy of this book, point your Internet browser here.

Tom Briggs is a fire service veteran of over 33 years and author of Vertical Academy, a vocational rope rescue textbook. Before retiring as a Captain in 2008, he was assigned to the Special Operations Division at Metro Fire Sacramento, California as the Rescue Services Manager. He was also a Rescue Team Leader for FEMA Urban Search and Rescue Taskforce 7. An instructor for the State of California and Rescue 3 International, Tom coordinated and taught many training courses specializing in the rope, trench, confined space, and water rescue disciplines to scores of agencies, often alongside many well-known rescue training luminaries.

The National Association of Search and Rescue (NASAR) recognized Tom’s training contributions in 1996 with the Higgins Langley Award.

Prusiks rigged with a PMP create reliable, hands-free progress capture mechanisms capable of holding 1,000 to 2,500 lbs. before slipping, depending on the rope and cord used.

PMPs usually have side plates that present a flat obstacle to the prusik hitch that is perpendicular to the rope direction. They must be rigged and operated properly for safe, smooth operation.

Prusiks integrated with PMPs for the purpose of capturing the hauling progress of a pulley system will completely support the load when the haulers stop pulling, and engage if an accidental shock occurs.

For this reason, riggers must make sure that the prusik of a self-tending PMP brake is in line with the axis of the carabiner it is connected to. The pulley will rock out of the way when the prusik brake engages.

Gravity has an effect on self-tending prusik brakes that are rigged horizontally. The prusik loop will, of course, tighten and slack as the operation proceeds.

In the slack state, there is potential for the cord to foul in the rigging and suck into the pulley.

This problem can be minimized by orienting the self-tending rig so that the prusik loop droops down and clear of the pulley when slack. The prusik hitch itself tends to stay snug and intact better when rigged this way as well.

Note: Riggers must ensure that the pulley is appropriate for the rope used, and that the rope enters and exits the pulley properly.

• The prusik hitch must stay intact and snug when the rope is moving while hauling the load up. 
• When the hauling rope incorrectly enters and exits the PMP at a wide angle, the prusik hitch sideswipes the side plates instead of contacting them flat and clean. This often results in the prusik getting partially sucked inside the pulley and loosening it enough to make it ineffective. This situation also increases friction and wear enough to damage the prusik cord and make hauling difficult. 
• Self-tending prusik brakes work best when the rope is parallel with itself as it winds in and out of the PMP. 
• Some PMPs are designed to tolerate wider angles, but they're not foolproof. 
• Monitor the rigging and make sure your self-tending brakes are well set up and working properly.