HSE: Industrial rope access - investigation into items of personal ...

Some fall-arrest systems and techniques require the deployment of a guided type fall arrester for
a flexible anchorage line. This type of fall arrester, defined in BS EN 353-2 9 , has to travel along
the anchorage line, accompanying the user without requiring manual adjustment during upward
or downward changes of position, but locking onto the line when a fall occurs.
The main advantage of a fall arrest system over a work positioning system is that it allows faster
movement both up and down the rope. Some devices can also work independently with no input
from the user. The back-up system device can be ignored while the user changes position.
However, as it hangs below the user, and may not ‘grab’ until the user has fallen some distance,
fall factors related to the device can be greater than two, and the device must be able to handle
the resultant forces safely. To limit the length of the fall, the link (or cow’s tail) to the harness
should be as short as possible. This system has the following drawbacks:
The back-up device should be positioned to minimise any fall which may be incurred. To this
end, it should always be positioned at, or above, the attachment point of the connecting link, or
cow’s tail, to the operative. To allow for this positioning the back-up device must have a
positive hold on the rope, so that the operative can slide it up or down the rope, position it, and
know that it will stay there until he or she moves it. The force necessary to tow the device, or to
dislodge it from its position, should be known. With a work positioning system, movement may
not be as simple but the user should always be in a safer position, particularly if the user
remains in one place for any length of time. The back-up system can then be adjusted so that an
actual fall is prevented.
Some manufacturers have recognised these issues and have attempted to create fall arrest
devices that can be locked in position when required. One of these is the Komet ‘Stick Run’,
which features a catch that adds or removes the cam’s sprung action. Without the spring, the
device runs very freely: when it is installed it will not. Similarly, the instructions for the Troll
‘Rocker’ illustrate how a second karabiner can be used to prevent the device moving freely on
the rope.
To be able to slide up and down the rope, without snagging, it is virtually certain that a device
without aggressive teeth will be needed. This is also a factor in considering what effect the
device might have on the rope should a limited fall occur. The device should be such that no
possible fall could damage the rope to the point of stripping the sheath.
It is essential that the device can be attached to, and removed from, the rope at any point. It then
follows that this method of attachment should be practical in everyday use, and that it should be
secure.
It is highly desirable that the device should be deliberately releasable while under load. This
makes it far more practical as back-up during descent, so that if the device does become loaded,
it can be recovered without the user having to climb back up the rope. At the same time, it must
be certain that, either by product design or by operator training, any possibility of the device
slipping, because of panic grabbing, is eliminated.
There may be reasons to deploy the back-up device on a link, or cow’s tail (lanyard), of any
length from a few centimetres, e.g. a connecter, up to the ‘reach’ of the individual operator. It is
highly desirable that the back-up device can be deployed at the end of lanyards covering this
range. (Say 10 cm to 100 cm.)
9 BRITISH STANDARDS INSTITUTION
BS EN 353-2: 1993 Personal protective equipment against falls from a height: guided type fall
arresters Part 2 Specification for guided type fall arresters on a flexible anchorage line
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