Fleet Maintenance - 22

can require cleaning every 50,000 to 75,000 miles,
he says.
Even with cleanings every 100,000 miles or
so, fleets should watch for increased frequency
of regenerations. This is a sign the DPF needs
cleaning, or possible replacement.
"What happens is when the ash builds up, the
regenerations start happening more frequently ...
[and] when you regenerate more frequently, two
things are happening," Anderson says. "One, you're
using more fuel, which costs the fleet money. And
two, it's hardening the ash plug, which makes it
more difficult to clean out over many, many thousands of miles."
To remove that ash buildup, Anderson says,
"Our philosophy has been to clean [the DPF] using
dry air with an air scanning approach - it's often
referred to as air knife technology. It's bidirectional air scanning of the filter."
This method cleans both ends of the DPF, and
according to Anderson, is "the most effective
and only OEM-approved cleaning system on
the market."
Clean Diesel Specialists takes a bit of a different
approach when cleaning DPFs. Koukal provides
a step-by-step explanation of how they go from
inspection to final testing of their DPFs.
Ü The substrate, temperature/pressure ports, and
gasket mounting surfaces are checked to ensure
there is no damage or corrosion.
Ü The flow of the filter is checked.
Ü The filter is weighed.
Ü Then, the filter is blasted with air and water
until no particulate matter is seen.
Ü The filter is then baked and goes through a postbake air blast.
Ü The filter is inspected for proper flow and cell
depth/health.
Ü If the filter fails any of these tests, the process
is repeated.
"In our experience, the way to ensure the filter
is as clean as possible is to put the filter through
a thermal regeneration to oxidation by baking in
a kiln," Koukal says. "This ensures as much of the
particulate has been processed as possible. We also
firmly believe in using a manual cleaning system
over automated. By having a technician physically
clean the filter, they can focus on problem areas
that an automated process cannot. While filter flow
specs can be a good reference tool for filter cleanliness it cannot be the deciding factor. Pin rod testing
and light testing, along with weight and flow, can
ensure a filter's health much more consistently
[than filter flow specs by themselves]."
Aside from FSX Equipment and Clean Diesel
Specialists' cleaning methods, there is also pulse
cleaning. This cleaning method may not get the
DPF fully clean, Anderson notes, as the air tends to
take the path of least resistance, especially when
using an automated system. Once a path is created
with the first air pulse, the remaining pulses will
likely follow that same path leaving particulate
matter behind.
Liquid or wet cleaning is another approach. This
method uses water to flush the DPF out, which
Anderson warns could actually make it harder
to clean. The water mixes with the ash and other
particulate matter creating a sludge, which can plug
the micro pores and is more difficult to remove.

22 Fleet Maintenance | May 2020

»FSX Equipment uses air knife
technology, or bidirectional air scanning
of the filter, to clean DPFs.

that are significantly cheaper than industry standard or offer unrealistic turnaround times."

Photo courtesy of FSX Equipment

Ultimately, fleets opting to clean DPFs, whether in-house or through an outside DPF cleaning
provider, must decide which process gives them
the best results. That may include solely a wet
cleaning or pulse cleaning method, or some combination of methods.
DPF cleaning equipment considerations
Cleaning DPFs in-house requires consideration of
the method of cleaning the fleet will be using as
well as protective gear for the technicians cleaning
the DPFs and proper disposal methods for the ash
and particulate matter.
Cost and maintenance of the cleaning equipment are two major factors to keep in mind when
deciding whether to clean in-house. Navistar's Just
points out the equipment could also call for an
increase in electrical capacity or a need to upgrade
the shop's air compressor system to get the volume
necessary for pneumatic cleaning equipment.
As for personal protective equipment needed
for the technicians doing the cleaning, gloves and
dust masks are recommended. Once the filter goes
into the machine for cleaning, Anderson says, it is
safe, as the ash and PM are being vacuumed into
a two-stage dust collection system with a HEPA
filter. HEPA filters are designed to contain very
fine particles.
Disposing of the ash and PM from the cleaned
DPF must be done in an appropriate manner. Roy
Horton, director of product strategy for Mack
Trucks, a manufacturer of heavy duty Class 8
trucks, engines, and transmissions, advises fleets
follow all local, state, and federal guidelines for
all handling and disposal measures.
On the other hand, if you are looking for a facility to clean DPFs, then Clean Diesel Specialists'
Koukal suggests fleets "find a cleaning facility that
has the knowledge and expertise to properly clean
a filter. Beware of companies offering cleanings

When to replace a DPF

With proper care and maintenance, the DPF
should last the life of the truck, but this is not
always the case. When cleaning the DPF there are
signs technicians can look for indicating the DPF
is no longer fit for service as well as tests that can
be run on the filter.
At FSX Equipment, they perform three tests to
ensure the DPF is in healthy, working condition.
First is a visual inspection, Anderson says. If any
black soot is coming out the outlet end of the filter,
this could signify a crack or melt inside.
The next test can confirm whether there is a
crack or melting inside with FSX's bypass detection. If there is any particulate matter coming all
the way through the filter, Anderson says, this will
be observed in the first 30 seconds of cleaning,
identifying it as a failed filter.
Lastly is the test flow bench, which will measure
the pressure or breathability index of the DPF. The
flow number is then compared with a baseline
chart that will tell the operator if the filter is in
the green, orange, or red range, Anderson explains.
Green means the filter is in excellent operating
service, orange means the filter is still good, but
may require cleaning sooner, and red means the
filter has sustained damage and should be replaced.
When replacing a DPF, fleets have three options
available: OEM, aftermarket, and remanufactured.
OEM filters
An OEM or original equipment manufacturer DPF
comes from the original truck manufacturer.
"The nice thing about [OEM DPFs is] we know
we're providing our customers a component that
is certified to original manufacturing, meaning it
meets EPA/CARB [California Air Resource Board]
certifications that are required for that engine
emissions model year," Navistar's Just says.
Though OEM DPFs meet the efficiency standards
set, Anderson advises they tend to be rather cost-

Fleet Maintenance

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