august2022 - 17

start burning at 650 to 700 degrees F. Spontaneous
combustion won't occur until 850 to 900 degrees F.
The normal operating temperature range for tires
is between 100 and 150 degrees F.
" Tires contain a great deal of potential energy, "
Arnold explained. " They are like high-grade coal
when they start to burn, and they are very difficult
to extinguish. "
When a tire comes apart while driving, it's
usually the result of underinflation, Arnold added.
Heat generated within the sidewalls as the tire
flexes weakens the steel belts in the casing while
softening the rubber to the point it eventually
breaks down and the tire blows apart.
With tire fires, the heat source is the wheel end.
Heat travels through the metal of the hub and
through the wheel, where it meets the tire bead.
Since the bead is built differently from the upper
sidewall, the rubber there gets hotter and hotter
until it begins burning, rather than exploding as
the casing might because of underinflation.
The source of that heat is friction from either a
deteriorating wheel bearing or a dragging brake.
In the bearing's case, failure usually stems from
lack of lubrication. Brakes can drag due to multiple
causes.
What do these " connected " wheel-end technologies
monitor to help avoid the most extreme or
the most minor maintenance problems? Generally,
anything that causes excess heating and vibration
in the wheel system-anything that could cause a
thermal event-even in the tire itself.
A typical wheel-end system comprises a seal,
an inboard and outboard tapered bearing, and
a hubcap. Additional wheel-end components
include a spindle nut and wheel nuts, and some
wheel-end systems may also contain a spacer that
is meant to provide preset torquing.
Each of these components plays a vital role in
protecting the wheel end as well as the operator.
Where wheel-end monitoring comes into play
is when the trailer or tractor is in motion-detecting
and flagging problems before or after the time
when wheel ends are inspected to ensure safety
and maximize performance.
Scheduled inspections help determine if a
wheel-end repair is necessary, but monitoring
systems give fleets and technicians clues about
what might be amiss even before the trailer or
tractor makes it to the shop for examination.
Stop your ignition
Rubber compounds begin to break down
when tire temperatures exceed 250 degrees
F, warned Phil Arnold, a former product
engineer with Michelin North America, at
the 2018 American Trucking Associations'
Technology and Maintenance Council Fall
Meeting. That's when a blowout might occur
that results from the deterioration of a tire.
The most extreme thermal event-fire-
can begin when rubber reaches temperatures
of 500 to 550 degrees F and flammable
vapors are emitted from the tire. If an ignition
source is present, the tire rubber will
Sensing danger
Monitoring systems are all about the data, according
to Paul Washicko, VP and general manager
of ConMet's digital business unit. He detailed
at length the PreSet Plus SmartHub, which is
ConMet's connected wheel health monitoring
system integrated into a hub assembly that " generates
actionable intelligence on wheel-end health, "
according to the manufacturer.
Washicko said the low-power electronic sensor
of the PreSet Plus SmartHub installs to the barrel
of the wheel hub and transmits data to a " gateway "
(installed on the bogey underneath a trailer
or under the dash on a tractor), sending data
from that " vehicle area network " to the SmartHub's
interface dashboard or to common trucking
industry telematics products such as Geotab, Lytx,
August 2022 | FleetMaintenance.com
17
Burning money
ConMet, maker of the PreSet Plus
SmartHub, studied the cost of key downtime
events, which can sometimes be
astronomical, and found the following:
* Roadside repairs: $1,150 per event.
* Unplanned maintenance: $3,750,
or four times the cost of each
planned maintenance event.
* Catastrophic thermal events:
More than $400,000 per event.
* Catastrophic wheel-offs: Up to-or
more than-$1.5 million per event,
which can include significant trailer and
cargo damage and even fatalities.
Furthermore, SKF reported its TraX
wheel-end monitoring system for
trucks, trailers, and buses may slash
unplanned maintenance and downtime
costs by as much as $3.6 million yearly,
based on a fleet of 5,000 trailers, and
can also help avoid thermal events.
Samsara, Solera (Omnitracs), and others about
wheel end, brake, bearing, and tire health.
" We have all this data, and we understand when
a component gets to a temperature where it's failing, "
Washicko said. " We've taken advantage of the
low-power electronics where we can actually put
this out in the real world with fleets, monitoring
temperature and vibration to see the health of the
wheel end. We can separate out the frequencies
of bearings and tires.
" It's interesting how we're able to separate
out those tire issues from bearing problems, "
Washicko continued. " We've been able to pick up
a bearing failure so early that a mechanic is not
able to detect it. " He also said ConMet's system
picks up on flat spots in tires, misalignments, and
even objects lodged in tires based on their different
frequencies detected by the sensor.
Alerts from the SmartHub most often pertain to
tires, steer tires especially, he explained. ConMet
partners with more than 60 fleets to use the
SmartHub system, Washicko said.
" We find out remarkable things about this
system every day, " he said. " Fleets don't expect
the alerts. We're giving them visibility that we've
never had before. We've picked up three different
» A breakdown of ConMet's wheel-hub assembly.
Photo: ConMet
http://www.FleetMaintenance.com
august2022

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