On many demolition and sorting jobs, material is left in uneven piles. Some stacks build up naturally during processing, others are pushed together to clear space quickly.
At first glance, higher stacks seem efficient. More material in one place means fewer movements.
But this often slows down grab handling more than expected when using Selector Grabs.
As stack height increases, material becomes less stable. Weight shifts unevenly through the pile, and the top layers are not properly supported.
Instead of sitting compact, the material starts to move independently.
This affects how the grab closes and holds the load.
You approach a high stack and position the grab.
As the grab closes, the top section moves before the lower material is secured. Pieces slide away or shift sideways, reducing the amount of material actually captured.
Even when the grab closes fully, the load is often unbalanced.
Then, during lifting or slewing, smaller pieces fall away or the load shifts inside the grab.
Compared to a lower, compact stack, the same machine takes more attempts to achieve a stable lift.
Working on high stacks leads to:
Over time, this reduces overall processing speed and creates additional handling work.
Operators often compensate by slowing movements, which further affects efficiency.
When material is kept at a controlled stack height, the grab can engage the load more evenly.
Instead of chasing loose top layers, the grab closes around material that is already supported.
You will notice:
A TocDem grab working on well-managed stacks maintains control without needing repeated adjustments.
Before grabbing, manage the pile rather than going straight into lifting.
Keep stacks:
If stacks are already too high, reduce the top layer first.
Approach from the side where the material is most stable, not necessarily where it is easiest to reach.
This allows Selector Grabs to close around supported material rather than loose fragments.
It is easy to assume that bigger piles mean fewer movements and faster work.
In reality, unstable stacks increase handling time.
Surface visibility also plays a role. Operators see more material in one place and expect quicker loading, without accounting for how that material behaves when gripped.
Grab performance depends on how the load is presented.
Key factors:
Even a well-maintained unit will struggle to hold unstable loads if the stack height is excessive.
Is it always better to keep stacks low?
Not necessarily low, but controlled. The goal is stability, not minimum height.
Does stack height affect all materials the same way?
No. Mixed or irregular materials become unstable much faster than uniform loads.
Can operator technique overcome high stacks?
Technique helps, but it cannot fully compensate for unstable material behaviour.
Control stack height before grabbing.
Stable, evenly distributed material allows the grab to work efficiently, reduces rehandling and keeps the job moving without unnecessary delays.
