MINING TYRES
There is still a lot to learn about how mining
tyres perform long term on autonomous fleets,
but it isn’t all good news
continue through them at constant speed
resulting in severe tyre deflection and vehicle
loping leading to excessive dynamic stress of
truck suspensions, frames and tyres.”
There is also the question of relative speed
changes. “Autonomous haul trucks operate in
one of two modes – acceleration or braking; they
are never coasting under zero throttle as is
common with manned trucks. As an autonomous
truck approaches a section of roadway that is
zoned for a different speed (higher or lower), it
will apply either full acceleration or substantive
braking effort to ensure that its crosses the
transition point at the precise stipulated speed.
This generates additional tyre slip relative to the
road surface increasing tread abrasion and wear
rate.”
So while autonomous systems are constantly
being reviewed and improved; from a mining tyre
perspective Cutler argues that the issues most in
need of further development are randomised
tracking, road pothole and depression
management, and acceleration and braking
management.
Another issue is that the mining companies at
the forefront of autonomous haulage are doing it
to maximise productivity, so in this sense they
also tend to push the envelope of truck and tyre
performance. And up till now most mines running
autonomous trucks have been set up for them
from the outset (notably in regard to haul road
design); “demand for autonomous in future will
mainly be retrofits to existing fleets on mines not
originally designed to autonomous requirements
leading invariably to tyre and other issues.”
Most autonomous systems require a haul road
significantly wider than that acceptable for
manned-haulage. “This is partly to minimise
haulage disruptions arising when an
autonomous truck detects another vehicle within
its zone of influence and partly for safety. While
this requirement will almost certainly be eased
with system maturity and confidence, it is still
likely to pose issues in the short
term with sites designed for
manned-trucks that are now
being retrofitted as
autonomous.”
As it already stands
conventional mine haul roads are
too often designed and
constructed using a “seat-of-the-
pants” approach and this needs
to change with more autonomy
rollout. “The mining industry
needs to undergo a cultural shift
and incorporate civil engineering
design and practices into making
haulage roads,” says Cutler.
“Mining companies have never been good at
building superelevation into roadway curves. The
problems this creates – tyre and truck
component stress, and rock spillage – are
compounded with larger tyres and autonomous
operation. Large earthmover tyres, especially 63
in used on ultraclass trucks, are more
susceptible to lateral stress damage associated
with negotiating curves and turns at excessive
speed for the curve radius and/or degree of
super-elevation. It is critical that mines planning
to adopt autonomous haulage properly manage
curve design in terms of radius, speed and
superelevation.”
Mines that have adopted autonomous haulage
are often routinely operating their haul truck
tyres at or in excess of their absolute work limits
in terms of maximum load and speed. This does
not just lead to a reduction in tyre life that can be
budgeted for; it is also likely to result in a
significant increase in ‘hot’ tyre incidents and
possibly smoking tyres or tyre fires – all of which
can be very disruptive to haulage efficiency.
“It is not uncommon for tyres running on
autonomous trucks to be operating safely within
their TKPH limits but exceeding their maximum
load and speed ratings leading to significant tyre
issues that have a substantial negative effect on
both tyre life and haulage productivity. “
Finally on safety, tyre fires on manned truck
fleets are rare – because drivers readily identify
‘hot’ tyres through smell or smoke. “With an
autonomous truck there is no operator to detect
hot tyres and no commercial monitoring system
currently available to act as a driver proxy. This
has already become a significant issue for some
autonomous operations.”
Offering a full service
In service terms Michelin says it offers its
customers a multi-level customised suite of
services and solutions to help customers better
understand how the tyres perform at their sites
specifically based on their site conditions, ways
to improve usage such as maximising tyre life or
increasing load, and the roles tyres and services
play in helping achieve the customer’s overall
objectives. “Services has always been a
differentiator for Michelin Mining. Our customer
support teams who work directly with our mining
customers are highly-valued for their service and
expertise. We hear this point reiterated time and
time again from our customers. Tyres play a vital
role with mining equipment, so customers want
to maximise the vehicle’s usage and productivity
while ensuring the operator and site personnel
are kept safe. Our customer support teams work
directly with customers on achieving these
objectives among others.”
The service offer starts with basic support to
help maximise tyre life, including Customer
Engineering Support and scrap tyre analysis
along with fleet inspections. Then there are the
more advanced offers via monitoring systems
like MEMS, and consulting which includes
solutions for collaborative planning and
forecasting, site and asset optimisation, as well
as customised analysis of data to boost
productivity.
Nick Davis at Goodyear states: “It’s critical for
mining operations to work closely with their tyre
suppliers to help optimise equipment uptime and
tyre performance, and drive down operating
costs. Goodyear provides expert field support for
mining operations. This includes field
consultations, tyre surveys, site audits, TKPH
studies and footprint evaluations, to name a few.
Our tyre experts are always available to provide
their experience and expertise.”
Bridgestone’s Netzel adds: “As the market
evolves, customer expectations are increasing
exponentially. Today’s customers expect more
than just great products from a tyre
manufacturer. They require steady product
supply, field engineering, and tyre monitoring
and maintenance solutions that help maximise
their investment – along with a trusted and
accessible dealer network to support their
operation in a truly integrated way. The
Bridgestone OTR global dealer network is one of
the largest and most capable of providing
comprehensive solutions across the lifecycle of a
tyre. This complete package of products,
technologies and services is the leading
differentiator when it comes to meeting the
needs of the sophisticated mining customer.”
Mining tyre recycling
The latest growth industry related to EM tyres is
the recycling of mining tyres to stop their
disposal in waste dumps and to recover their
component materials for reuse. Tony Cutler
states: “Brazil was the first mining jurisdiction –
over ten years ago – to legislate on mining tyre
disposal and recycling to reduce malaria and
similar diseases associated with discarded tyres
JULY 2019 | International Mining 51