Fleet Maintenance - 20

(OEM), buy aftermarket, or buy remanufactured.
Each option has its benefits and drawbacks, which
will be discussed later in the article.
For fleets to keep their DPFs functional, it is
crucial they understand proper maintenance,
cleaning methods, and replacement options,
when necessary.

DPF Cleaning Process

How do DPFs work?

In order to understand how to maintain a DPF,
it is important to first know how the DPF works.
As the DPF collects particulate matter and ash
from the engine, that matter is filling the DPF,
creating a backpressure within the filter.
"[Once the] backpressure reaches a certain
threshold, a regeneration to oxidation is performed,"
explains Ryan Koukal, chief operating officer for
Clean Diesel Specialists. "Oxidation occurs when
the particulate matter is broken down into gases
and non-combustible material. The non-combustible material, along with ash from oil consumption,
cannot be removed from the filter, requiring the
filter to be cleaned periodically."
Clean Diesel Specialists services DPFs and
diesel oxidation catalysts (DOCs) to help reduce
diesel fuel's carbon footprint on the environment.
Regenerations within the DPF are necessary to
"clean-out" as much of the engine particulates as
possible. If regeneration does not occur periodically it could create problems with the engine.
Three types of regenerations can occur: passive,
active, and forced.
Passive regeneration
Passive regeneration occurs during normal vehicle operation.
"When the DPF hits a specific temperature
[around 1,112 degrees F], it goes into a regeneration cycle," says Cory Just, director of dealer field
service for Navistar, a manufacturer of commercial trucks, buses, and engines. "It converts the
soot [particulate matter] into ash which is a much
smaller particle of waste from the engine, and it's
trapped within the DPF."
There is no outside influence prompting the
passive regeneration cycle to begin. In fact, other
than a possible dash light appearing during the
process, the driver will have no knowledge of the
regeneration occurring at all.
According to Koukal, this form of regeneration
typically occurs in vehicles with a high duty cycle,
such as long-haul trucks.
Active regeneration
If the aftertreatment system does not reach 1,112
degrees F, the engine control module (ECM) on
the vehicle will activate an active regeneration
cycle, Just explains.
"The turbo will change the pitch of the vanes
to increase the load on the engine creating higher exhaust temperatures," Koukal says. "Once the
temperatures reach a specific range, the system
will inject atomized diesel fuel into the exhaust
by either injecting fuel on the exhaust stroke of a
cylinder or using a 'seventh' injector mounted in the
exhaust after the turbo. That fuel reacts with the
precious metals in the DOC to create heat. That heat
then oxidizes the particulate matter in the DPF."

20 Fleet Maintenance | May 2020

After inspection, Clean Diesel Specialists
start their cleaning process by testing the
flow rate of the DPF. Currently, no set standard
exists for what the flow rate should be - "good"
and "bad" rates will fluctuate depending on the
cleaning equipment and filter itself.


Photo courtesy of Clean Diesel Specialists

Whether an active regeneration takes place
depends on the driving cycles of the vehicle, Just
says. This means active regeneration could happen
as often as once a week, or even daily. It is also
possible that active regeneration could never take
place throughout the life of the vehicle.
Typically though, this kind of regeneration
happens on vehicles with lower duty cycles as well
as those with the capability for longer drive cycles,
such as trucks with local routes, Koukal notes.
Forced regeneration
A forced regeneration is similar to an active regeneration but calls for driver intervention. The same
actions will take place as with the active regeneration, but instead of the ECM activating the
regeneration, the driver initiates it.
"If [there is] prolonged use of the vehicle where
it does not reach that [1,112 degrees F] and active
regeneration is not able to occur, the driver is alerted with various warnings, [such as] warning lights
on the dash," Just says.
It is then recommended that the driver pulls
over and activates a regeneration cycle and waits
for the cycle to complete.
Failing to activate the regeneration or not
waiting for it to complete could lead to the vehicle derating, Koukal warns. Designed to prevent
damage to the engine and aftertreatment system,
the ECM will limit vehicle speed or power to initiate a derate. If the driver gets back on the road
while the truck is derating, this may cause problems with the engine and a technician may have
to step in to force another regeneration.

Maintaining a DPF

Proper maintenance for a DPF involves two parts:
a preventive maintenance schedule and an effective cleaning method.

Next, the filter is weighed. Knowing how
much soot comes out of the DPF after
cleaning can help determine the health of the
truck or equipment.


Photo courtesy of Clean Diesel Specialists

		»This image shows a clean filter (left), a
dirty filter plugged with ash and particulate
matter (center), and a melted filter (right).
Photo courtesy of Clean Diesel Specialists

Preventive maintenance
Preventive maintenance for the DPF is more than
just caring for the DPF, it means taking the time
to maintain the aftertreatment system as a whole.
"Perform visual inspections at regular [preventive maintenance] scheduled service intervals looking for exhaust leaks [and] fluid leaks
upstream, [as well as] perform required maintenance on the aftertreatment hydrocarbon injector," says John Moore, product marketing manager
- powertrain for Volvo Trucks North America, a
global truck manufacturer.
Additionally, Moore notes, be sure not to ignore
regeneration requests.
"System performance is compromised when
regenerations are continuously interrupted,"
he says.
Kelly Gedert, vice president of on-highway
market development for Daimler Trucks North
America, a heavy duty truck manufacturer,
provides a list of additional recommended preventive maintenance practices for keeping an aftertreatment system healthy:
Ü	Every 24 months, fill the diesel exhaust fluid
(DEF) pump air bladder to 40 to 46.4 psi of air.
Ü	Change the main filter of the DEF pump every
500,000 miles for 2017 and newer engines, adhering to 2017 greenhouse gas emissions standards.


Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance

Uptime: Expecting the unexpected
Editor's Note: Catching up on fleet maintenance
Maintenance considerations for manual versus automated manual transmissions
DPFs: Clean or replace?
Why Identify and track vehicle warranties?
Lube it or lose it
OTA: Supporting uptime remotely
Management: How fleets can benefit from having a SAMP
Training: Supporting today's students and tomorrow's techs
Diagnostics: Assessing aftermarket diagnostic solutions
Fleet Part & Components
Tools & Equipment
Guest Editorial: Keeping tire pressure at optimum levels
Fleet Maintenance - 1
Fleet Maintenance - 2
Fleet Maintenance - 3
Fleet Maintenance - 4
Fleet Maintenance - 5
Fleet Maintenance - 6
Fleet Maintenance - 7
Fleet Maintenance - Uptime: Expecting the unexpected
Fleet Maintenance - 9
Fleet Maintenance - Editor's Note: Catching up on fleet maintenance
Fleet Maintenance - 11
Fleet Maintenance - Maintenance considerations for manual versus automated manual transmissions
Fleet Maintenance - 13
Fleet Maintenance - 14
Fleet Maintenance - 15
Fleet Maintenance - 16
Fleet Maintenance - 17
Fleet Maintenance - DPFs: Clean or replace?
Fleet Maintenance - 19
Fleet Maintenance - 20
Fleet Maintenance - 21
Fleet Maintenance - 22
Fleet Maintenance - 23
Fleet Maintenance - Why Identify and track vehicle warranties?
Fleet Maintenance - 25
Fleet Maintenance - 26
Fleet Maintenance - 27
Fleet Maintenance - 28
Fleet Maintenance - 29
Fleet Maintenance - Lube it or lose it
Fleet Maintenance - 31
Fleet Maintenance - 32
Fleet Maintenance - 33
Fleet Maintenance - OTA: Supporting uptime remotely
Fleet Maintenance - 35
Fleet Maintenance - Management: How fleets can benefit from having a SAMP
Fleet Maintenance - Training: Supporting today's students and tomorrow's techs
Fleet Maintenance - Diagnostics: Assessing aftermarket diagnostic solutions
Fleet Maintenance - 39
Fleet Maintenance - Fleet Part & Components
Fleet Maintenance - Tools & Equipment
Fleet Maintenance - Guest Editorial: Keeping tire pressure at optimum levels
Fleet Maintenance - 43
Fleet Maintenance - 44