february2023 - 36

GUE ST EDITORIA L
» DPF cleaning and replacements range
between $2,500 to $8,000 per vehicle.
Pre-heating the engine with a fuel-operated
heater can increase their lifespan and reduce
maintenance departments' repair load.
Webasto
And how much does your fleet spend annually
to replace damaged and inoperable DPFs?
According to the survey, 65% drew a blank on
this question as well.
Finally, do you have any idea how many
hours longhaul trucks spend idling each year
and what percentage of a vehicle's running
time this represents? According to the U.S.
Department of Energy, a longhaul truck idles
about 1,800 hours per year, and uses about
1,500 gallons of fuel to do so. And industry
experts suggest that it's not unusual for idling
time to represent as much as 45 to 50% of a
vehicle's running time. Don't feel bad if you
didn't know the answer to this one either, most
maintenance folks don't.
How fuel-operated
heaters ease
aftertreatment issues
Diesel particulate filter issues can be the bane of a
maintenance department, but pre-conditioning engines
can drastically (and economically) improve efficiency.
Fuel-operated heaters have been around for
decades, but it's surprising how little many
maintenance professionals know about them
and the benefits they provide. Let's change that
right now with a pop quiz.
First, here's a simple question. Which runs
dirtier: a cold or warm diesel engine? Of course,
you know that a cold diesel engine puts out a lot
more soot and particulate matter. Folks always
answer that correctly when I ask.
Here's another. Which uses more fuel and
By Duane Bratvold
WESTERN REGIONAL SALES MANAGER,
CUSTOMIZED SOLUTIONS, AMERICAS REGION,
WEBASTO GROUP
Duane Bratvold serves as Western regional sales
manager, customized solutions, Americas Region for
Webasto Group. Bratvold uses his expertise in emissions
standards to provide FOH and other emissions
management solutions for fleets of trucks, buses, and
off-highway equipment.
puts out more emissions: a big diesel engine
or a tiny fuel-operated heater? The big one,
obviously, as the heater burns relatively very
little fuel, and thus a small fraction of the
engine's emissions output. Most get this one
right as well.
How about a tougher math question: How
much does your fleet spend annually on DPF
cleaning? If you're anything like 87% of the
maintenance professionals surveyed in a
recent fleet study conducted by Webasto-in
conjunction with Fleet Maintenance-you don't
know the answer to this very important question.
You probably should.
36 Fleet Maintenance | February 2023
The down and dirty on DPFs
Let's start with some very basic, but important,
facts. Until an engine is operating at between
842 to 1,112 degrees F, which is common at
road speeds and well above idling temperature,
the DPF is essentially used as a 'garbage
can' for the collection of soot and PM. The DPF
is a temperature-dependent device, so without
sufficient exhaust operating temperatures,
the lifespan of every DPF will be negatively
impacted by lower operating temperatures.
Cold starting or idling a diesel engine basically
turns it into a soot- and smoke-generating
machine that feeds directly into the DPF.
The combination of un-combusted fuel and
PM create a heavy, wet, and dense coating
that forms on the surface of the DPF. The
contaminants increase backpressure, resulting
in significant reductions in engine and
DPF efficiency. Face plugging and filter overload
are generally the byproducts. Cold starts
also create the need for more frequent DPF
cleanings, which cost fleets time and money,
while shortening a DPF's effectiveness and
its lifespan.
Temperature-related issues can also occur
in vehicles with short duty cycles, such as lastmile
delivery. Frequent throttle-on and -off
sequences create the same type of sub-optimal
temperature and increased emissions
environment. The DPF's catalyst can't maintain
regeneration temperatures and the DPF
becomes overloaded, and plugging can result.
If one factors in downtime for DPF cleaning
and replacement, costs can range between
$2,500 to $8,000 per vehicle. It also adds up to
a lot of extra work for fleet maintenance folks-
work that could otherwise have been avoided.
As one fleet professional put it: " If you can
reduce the crud that's coming out of the stack
before it goes into the DPF, you've just won half
the battle right there. "
Needless to say, I agree.
february2023

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