“Fleets may not take into account the other
factors around it, like what is the failure rate of
the fi lter? If you get a really good cleaning process
and you can bring the failure rate down, but the
cost of cleaning goes up, you still actually win,
because you’re not replacing $2,000 fi lters as
oft en,” he adds.
Effects of different duty cycles
Vehicle idle time plays a signifi cant role in aft ertreatment
system performance. In addition, duty
cycle is an important consideration for the service
frequency of aft ertreatment systems.
“Depending upon how much idle time they
have, whether the engine is consuming engine oil,
the duty cycle — are they over the road or are they
stop-and-go; the environment such as the ambient
temperature — all those play a factor into how
oft en the aft ertreatment needs to be maintained,”
says Cummins’ Lightner.
Idling is detrimental to extending the life of
DPFs, says Webasto’s Bratvold.
“Idling at a truck stop, or when they’re out doing
their normal job during the day just ... absolutely
destroys a DPF. Th e DPF is so cold, all it is is like a
garbage can collecting soot, and then it gets to a
point there’s too much soot and it can’t overcome
it,” Bratvold explains.
Th is is because the engine aft ertreatment
system works most optimally at highway
speeds, when a vehicle’s engine gets hot enough
to complete a regeneration cycle. Any extended
idling means the vehicle’s engine is not
burning hot enough. Th is causes excessive
soot to collect in the DPF, versus allowing the
system to heat up to an optimal temperature to
burn off the soot into ash. Technicians can complete
forced regenerations, using a scan tool in the
30 Fleet Maintenance | November/December 2018
shop to complete this service. But that takes the
vehicle out of service as well.
Preventative measures
to consider
Bratvold recommends, based on studies conducted
at Webasto, that a coolant or engine heater can
aid in reducing the service requirements on an
aft ertreatment system.
“We’ve proven that in some of the tests that
we’ve done in the laboratory, where we’ve preheated
an engine and started it up, and we measured
the soot in that cold startup area,” says Webasto’s
Bratvold. “Just by preheating the engine you can
reduce that soot by 60-plus percent. If you can
stop that cold, wet, dense soot from going into the
DPF, until the DPF warms up to where it can start
to regenerate, you’ve beaten half the battle right
there.” Th is can be done through an engine heating
system, either specifi ed at purchase or installed
as an aft ermarket option.
If you can preheat (the engine) every day,
depending on your duty cycle, you can extend
those intervals — you can probably cut out three
to fi ve cleanings per year, depending on what your
duty cycle is,” Bratvold says. “Every time that DPF
gets full, if you do not deal with it then, right at
that time, then you run the risk of a contaminant
getting in there causing a catastrophic failure.”
Th ere are diff erent options to heat up the
engine, including a coolant heater and a plug-in
block heater. Th e heater must be turned on about
45 minutes before the driver gets in the cab to
start his or her route. Th is gives the system enough
time to warm up before the vehicle is turned on.
For maintenance on the engine heater, Bratvold
advises to turn it on at least 20 minutes per month,
even in warmer months, to ensure continued operation.
In addition, the fuel fi lter on the engine heater
should be changed annually.
With that, driver education is critical to ensure
system issues are addressed as quickly as possible.
“Operator error is probably the number-one failure
of a DPF,” Bratvold says. “A lot of these guys
will drive down the road and the light will come
on and they don’t want to stop, so they’ll just keep
driving it until something goes wrong and they’re
forced to pull over.”
“If a light comes on, you have to deal with it
immediately,” Bratvold adds. “You need to understand
who is cleaning your fi lters and make sure
they have the expertise to fi nd issues and not just
send you back the fi lter.”
If a fl eet employs a fi lter exchange program,
Emission & Cooling Solutions’ Griffi th also
suggests going through a single-source provider
to service DPFs. Th is allows for complete data
collection of all fi lters through one provider,
versus going through multiple vendors.
“All that data comes into one place,” Griffi th
says. “And it should be compiled and it should be
presented as quarterly, monthly, yearly, however
they want it.”
It is also critical to ensure proper technician
training when it comes to coding maintenance
and service of the aft ertreatment system.
“If you have a DPF failure and you’re sending
the fi lter out for cleaning and you’re not getting
that (fi lter) back, fi nding a way to code
that as a failure is really the only way
to do it - making it a data point, basically,”
Griffi th says. “With the systems out
there now, everybody runs their own
proprietary kind of system, from what
I understand, just making sure that
people are recording it the correct way,
so you can identify that part as a failed
fi lter will lead to a better understanding
of failure rates.”
Takeaways and next steps
Emission & Cooling Solutions’ Griffi th
recommends every fl eet look at the total
cost of aft ertreatment - not just the price
of the replacement fi lter, but the cost of
cleaning, replacement programs and all
aspects of the service.
“Th ere are very few people who have
a good grasp on exactly how much their
aft ertreatment is costing them,” Griffi th
says. “We’re using data analytics to really
help people understand what their
failure rate is, as well as identifying ‘this
truck has a higher failure rate than this
truck.’ In the future, some people will
probably be using that when they spec
their trucks.”
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Both driver and technician
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