A lot of rope rescue technicians still don't understand the principles of fall factor. However, it's quite simple, even if you hated arithmetic. Fall Factor is simply the distance of the fall divided by the length of the rope or lanyard from the person falling to anchor point.
The equation looks like this;
Fall Factor = Length of Fall / Length of Rope/lanyard
Factor 2 is the maximum you will encounter in a typical un-arrested fall, since
the height of a fall can't exceed two times the length of the rope or lanyard.
Normally, a Fall Factor 2 can only occur when a technician is working above his
anchor point and at the maximum length of the rope or lanyard. The force is the
same if you fall 2 metres or 20 metres.
Your well being depends on
several factors, strength of your anchor, the stretch of the rope or deployment
of the energy absorber, strength of your connectors and finally the fit of your
Shock load is the result of three factors; the rope or energy
absorber, the fall factor, and the weight of the falling object.
Obviously, the only part of this equation that can drastically reduce
the force of a fall is the deployment of the energy absorber. So, safety systems
are designed around the shock-absorbing quality of the energy absorber. It
cushions the fall, reducing the impact force and the chance of system failure.
The energy absorber is the one element in the whole system that is designed to
limit the force of a rescue technicians’ weight in a worst-case fall (Fall
Factor 2) to not more that 6 kN. The rest of the system can be designed to work
with this known maximum force.
Static ropes are designed to minimise
stretch. Their ability to absorb shock is marginal, particularly along short
lengths of rope, and they transmit virtually all the shock load equally to the
anchor system and to the body. In a rescue situation, a very short fall can
develop enough force to be critical, especially with a casualty on board.
Therefore rope of choice for rescue applications must be a semi static
conforming to EN1891A and be of 11mm or 10.5mm in diameter. The compromise of
the stretch will be very useful when arresting a fall and one thing often
overlooked is the action of the various knots in the system to also tighten and
Webbing slings perform like static rope. Used for
anchoring and extending a connection, slings are just as rigid as static rope. A
Fall Factor 2 develops enough shock load to risk failure of the sling, the
wearers harness, karabiners, not to mention damage to the rescue technicians
A fall of less than four
feet on a static rope or sling can create enough shock force to cause serious
injury. The human body can only sustain, a shock force of 12 kN and loads of 18
kN are not only highly undesirable but very dangerous. In addition 18 kN is
getting close to the minimum limits of all the items in your rope system. A fall
factor 1.9 attached directly to a static rope running over a karabiner or
pulley, with is normal shock force of 18 kN, becomes a shock force of 30 kN.
Would your anchor hold? It is academic, because something else would
Always ensure you’re protected by an energy absorber,
protect yourself from falling by the use of restraint techniques or if safe to
do so, use a fall arrest lanyard. Never work above your anchor point unless you
are very well protected. Use only semi static ropes and ensure the equipment
you use in the system is rated accordingly, e.g. sports climbing equipment has
very limited use in rescue.
The most valuable item you carry is your
brain, look at the problem and be sure you fully understand the consequences of
your actions and results of an accidental arrested fall.