PULLEYS:
A Tool for Every Rescuer’s Toolbox
S Y S T E M S
I N C ™.
© Gravitec Systems, Inc. 2009
A pulley is defined as a rolling sheave that
is used to change the direction of a rope and
the application of pulling force. By using pulleys in different applications, rescuers are able
to redirect ropes to suit the needs of the rescuer, reduce friction in a system and increase
the mechanical advantage of the system to lift
greater weight. Pulleys are very versatile and
necessary tools in every rescuer’s toolbox.
There are dozens of different types of pulleys
for many different types of industries. The
following paragraphs are specific to pulleys
commonly found and used during rope rescue
operations.
Many pulleys are designed to be “prusik
minding.” These pulleys are characterized by
square rather than rounded corners. Pulleys
commonly used in hauling systems redirect
the rope and create lifting systems with different mechanical advantages. As the hauling
system is created, a prusik hitch (or ascender)
is used to hold the rope when the hauling
system is being reloaded. When the rope is
being raised, the prusik will try to enter the
pulley. Prusik minding pulleys are machined
in such a manner that the side plates halt the
hitch, preventing it from entering the pulley
and allowing the rope to slide through.
The side plates of a pulley are designed to
capture the rope and offer strength to the
pulley. Most pulley plates are stainless steel
or aluminum. Most pulleys are split, meaning
the side plates can swivel. This is important
to enable installation (or removal) of a pulley
anywhere along the length of a rope. If the
side plates did not swivel, the rope would
have to be loaded from one end which would
effectively terminate most rescue operations.
A pulley’s connection eyes vary in size.
Smaller, personal pulleys usually accept one
carabiner and general purpose rescue pulleys
have larger holes which accept more than one
carabiner. Double sheave pulleys have three
plates, two sides and one center plate. All
three plates line up after the ropes have been
loaded, making a connection to the carabiner
possible.
FALL PROTECTION & RESCUE
www.gravitec.com 1.800.755.8455