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This chapter sets out working practices to reduce the risk of
injury from tree service chainsaws when working at height from
a rope and harness. While it may form the basis of guidance and
training literature, it should not be regarded as a substitute for
formal training.
General requirements working at height
Operators of tree service chainsaws working at height from a
rope and harness should never work alone. A competent ground
worker trained in appropriate emergency procedures should
assist them.
Operators of tree service chainsaws for this work should be
trained in general safe climbing and work positioning techniques
and shall properly equipped with harnesses, ropes, strops,
karabiners and other equipment for maintaining secure and safe
working positions for both themselves and the saw.
Preparing to use the saw in the tree
The chainsaw should checked, fuelled, started and warmed up by
the ground worker before it is sent up to the operator in the tree.
The chainsaw should be fitted with a suitable strop for attaching
to the operator's harness (Fig.1):
a) choke the strop around the attachment point on the rear of the
saw (Fig.6);
b) provide suitable karabiners to allow indirect (i.e. via the strop)
and direct attachment (i.e. at the attachment point on the saw)
of saw to the operators harness;
c) ensure the saw is securely attached when it is being sent up
to the operator;
d) ensure the saw it secured to the harness before it is
disconnected from the means of ascent.
The possibility to attach the unit on the operators belt greatly
reduces the risk of machine damage during aerial work. Stop the
machine when it is attached to the operator.
The saw should only be attached to the recommended attachment
points on the harness. These may be at mid-point (front or rear)
or at the sides. Where possible attaching the saw to centre rear
mid-point will keep it clear of climbing lines and support its weight
centrally down the operator's spine (Fig.2).
When moving the saw from any attachment point to another,
operators should ensure it is secured in the new position before
releasing it from the previous attachment point.
Using the chainsaw in the tree
An analysis of accidents with these saws during tree service
operations shows the primary cause as being inappropriate
one-handed use of the saw. In the vast majority of accidents,
operators fail to adopt a secure work position which allows them
WORKING WITH TREE SERVICE CHAIN-SAWS FROM A ROPE AND HARNESS
to hold both handles of the saw. This results in an increased risk
of injury due to:
- not having a firm grip on the saw if it kicks back;
- a lack of control of the saw such that it is more liable to contact
climbing lines and operators body (particularly the left hand
and arm)
- losing control from insecure work position resulting in contact
with the saw (unexpected movement during operation of the
saw)
Securing the work position for two-handed use
To allow the operator to hold the saw with both hands, they
should as general rule, aim for secure work position where they
are operating the saw at:
- hip level when cutting horizontal sections;
- solar plexus level when cutting vertical sections.
Where the operator is working close into vertical stems with a low
lateral forces on their work position, then a good footing may be
all that is needed to maintain a secure work position. However
as operators move away from the stem, they will need to take
steps to remove or counteract the increasing lateral forces by, for
example, a re-direct of the main line via a supplementary anchor
point or using an adjustable strop direct from the harness to a
supplementary anchor point (Fig.3).
Gaining a good footing at the working position can be assisted
by use of a temporary foot stirrup created from an endless sling
(Fig.4).
Starting the saw in the tree
When starting the saw in the tree, the operator should:
a) apply the chain brake before starting;
b) hold saw on either the left or right of the body when starting:
1) on the left side hold the saw with either the left hand on the
front handle or the right hand on the rear handle and thrust the
saw away from the body while holding the pull starter cord in
the other hand;
2) on the right side, hold the saw with the right hand on either
handle and thrust the saw away from the body while holding
the pull starter cord in the left hand.
The chain brake should always be engaged before lowering a
running saw onto its strop.
Operators should always check the saw has sufficient fuel before
undertaking critical cuts.
One-hand use of the chainsaw
Operators should not use tree service chainsaws one-handed in
place of unstable work positioning or in preference to a handsaw
when cutting small diameter wood at the branch tips.
English
Tree service chainsaws should only be used one-handed where:
- the operator cannot gain a work position enabling two-handed
use; and
- they need to support their working position with one hand; and
- the saw is being used at full stretch, at right angles to and out
of line with the operator's body (Fig.5).
Operators should never:
- cut with the kickback zone at the tip of the chainsaw guide bar
- 'hold and cut' sections
- attempt to catch falling sections.
Freeing a trapped saw
If the saw should become trapped during cutting, operators
should:
- switch off the saw and attach it securely to the tree inboard
(i.e. towards the trunk side) of the cut or to a separate tool
line;
- pull the saw from the kerf whilst lifting the branch as
necessary;
- if necessary, use a handsaw or second chain saw to release
the trapped saw by cutting a minimum of 30 cm away from the
trapped saw.
Whether a handsaw or a chainsaw is used to free a stuck saw,
the release cuts should always be outboard (toward the tips of
the branch), in order to prevent the saw being taken with the
section and further complicating the situation.
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