Grapple saws

Arborists are beginning to discover that by mounting a grapple saw – on an excavator or truck crane for example – they can work from the ground, removing the risks of using a chainsaw at height. The attachment grabs the section to be removed, and the saw then cuts it, avoiding the need to tie it off to the tree prior to cutting.

The use of this equipment poses a series of new risks, though.

On the machine side, there is concern about the unknown weight and balance of the load and how suddenly taking the weight at height affects the stability of the machine or the rated capacity indicator. On the human side, experts also warn of risks associated with the saw itself.

“A grapple saw can be an incredibly productive tool,” explained Rey Kell, Director of equipment supplier Forest Centre, “though they can present new risks and they are of course not a replacement for conventional methods for every job.

“Applied safely, some of the machine and attachment combos available to arborists today can be considered as a level-up or an extra arrow in the quiver for a crew with climbers, an EWP or bucket truck,” added Rey.

Different tools with different needs

Machine attachments with hydraulic chainsaws have been around for decades on purpose-built forestry carriers, while their application specific to the tree-care industry is relatively new. The number of highly specialised grapple-sawequipped truck cranes in Australia and New Zealand today, for example, could perhaps be counted on one hand.

Excavators, by comparison, are much easier to come by, and seemingly straightforward for equipping with a range of work tools such as grapples and mulching heads when operating close to the tree is possible. Small excavators with thumb grabs or hydraulic grapples are already well-utilised by many arb crews, and for many businesses there is little barrier to entry for taking the next step up to a larger excavator capable of more lift and reach for grapple-saw use.

“We are well-versed in hydraulic saw units from our years of supporting high-production forestry attachments here in Australia,” explained Rey from Forest Centre. “The basic concept is the same for grapple saws and felling grapples used in tree care, however not all units are alike in terms of their safety requirements. This is an area that requires careful evaluation in terms of the chosen attachment, but also your host equipment, operator training, work process and likely job sites.”

What is ‘Chainshot’?

One major difference in risk profile when moving between handheld chainsaws and hydraulic saw units is ‘Chainshot’.

Explained briefly in a previous AA issue, Chainshot is a phenomenon that can occur in mechanical harvesting and processing applications, as well as grapple-saw work. It is the high-velocity separation of a piece or pieces of cutting chain from the end of a broken chain. Chainshot occurs when the end of a broken chain is rapidly accelerated due to either an impact with a portion of the cutting head or a whip-like motion of the chain end. Chainshot can have as much kinetic energy as a bullet fired from a rifle, easily penetrating conventional safety-window material on mobile plant with potentially fatal consequences.

First, the saw chain breaks.
Second, after a saw chain breaks, the ‘free’ end of the saw chain begins to whip away from the break.
Third, if the saw chain is not contained by the saw box or a chain shot guard, the broken saw chain’s free end can speed up rapidly, carrying immense dynamic energy. Finally, at the peak of the whip, saw chain pieces may break loose and be ejected at high speed.

The ballistic considerations here alone require a risk zone for operators, other personnel, and members of the public of at least 90 metres, unless stated otherwise by the saw-attachment manufacturer. This risk-zone radius is business-as-usual for remote forest work sites, though for semi-urban or roadside work can require extra management, or even choosing an alternative approach.

For operator safety, an excavator’s factory front-window material should normally be replaced or supplemented with a protective screen of Lexan Margard or equivalent (a type of bulletproof glass) of at least 19mm thickness.

When choosing a grapple saw, consult your supplier and familiarise yourself with all recommendations in the manufacturer’s operating manuals. This will help clarify what exclusion zone will be required (and whether it will be practical) for your work, and what level of extra protection modifications are needed on your host machine.

“There is an increasing amount of choice in the attachment market,” offered Rey, “and until you know where on the risk spectrum your equipment sits, the bar and chain of an operating grapple saw should be treated like a loaded gun – pointed away from yourself and anyone else.”

Forest Centre is continuing to work with industry and regulatory bodies on safety awareness in ‘mechanised arb’ and has assembled some practical guidance information for tree-care workers on its website, which can be accessed at

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