Fleet Maintenance - 19

"All of these components and their related air
lines, valves, and solenoids can fail due to poor
air system maintenance," says Erik Johnson, sales
manager for Expello Air Products, manufacturer
of the Expello Automatic Drain Valve.

Guarding against water
contamination
As Bendix's Nagel points out, the biggest issue
with air brake systems over the past 50 years
has been moisture damage resulting from water
in the air tanks.
"Even in a well-operating system, water accumulation can occur in reservoir tanks," says Gerry
Mead, executive director of innovation at Phillips
Industries, a manufacturer and supplier of parts
for the trucking industry. That is simply the result
of moisture being in the air. Thus, air tanks on both
the truck and trailer must be monitored closely.
Expello Air's Johnson says daily draining of the
wet tank will remove any contaminants that get
past the air dryer.
"The use of automatic drain valves will remove
all the oil and water from the wet tank while the
vehicle is running - without placing the responsibility on the driver to manually drain the tanks,
which may be inaccessible anyway," Johnson says.
Expello Air's Automatic Drain Valve, for example,
replaces the manual drain petcock on a tank. It
purges water, oil, and dirt in one-second bursts
every five minutes while the vehicle is on.
In addition to draining the tanks, regular
inspection of the air dryer is important.
"The air dryer is the first line of defense against
water and oil entering the air system," Johnson says.
According to Nagel, dryers should be inspected
every two to three months. Technicians should
perform a manual blow-off and look for water and/
or oil coming out of the tank.
Another item fleets should think about is where
the air dryer is mounted. The engine compartment
and frame rail are two popular options.
"Many modern trucks have dryers with integrated multi-circuit protection," Nagel says. "The
governor, pressure protection valves, and purge
valve are all part of the dryer. If the dryer is
mounted on the frame rail, all of these components are subjected to road hazards, water, and
sometimes salt. With these types of dryers, a
potential failure mode is from valves extending from the bottom of the dryer. Every time the
dryer exhausts moisture, that area of the dryer
gets wet and begins to pick up dirt, which leads
to corrosion. If that corrosion becomes severe
enough, leaks can occur, and valves can begin to
malfunction."
Fleets should conduct a thorough visual inspection of the air dryer during the fall months.
"Dryers are often painted at the factory, but that
paint eventually begins to peel off," Nagel says.
"If operating in a harsh environment, it's okay
to spray paint the exterior of the dryer housing
because paint helps protect."
Another action Bendix recommends fleets take
is replacing the purge valve on the bottom of the
dryer every couple of years.
"Internal check valves are also easy to change,"
Nagel adds.

As for replacement of the dryer itself, lifecycles
vary based on how and where a truck operates.
That said, for normal over-the-road and regional
applications, most cartridges last a couple of years,
according to Nagel. On the other hand, severe duty
applications might require cartridge replacement
once or twice a year. Regular inspections will
help fleets determine the precise time to replace
a cartridge.
For tractor-trailer applications, fleets should not
neglect the gladhands. Lines are used to supply
a trailer with air to operate its braking system,
allowing air to flow from the tractor's air tanks
through a gladhand and into the trailer's tanks.
"Inspect gladhands regularly," Phillips
Industries' Mead advises. "Failure to properly
care for them allows moisture to penetrate the
air system."
Corrosion can be another big issue. Mead
suggests using powdercoated or anodized gladhands in highly corrosive environments.
Mead offers some additional advice on how to
properly care for gladhands:
Ü Replace if the small dimple on the connector
plate is worn
Ü Replace if heavy wear or corrosion is present on
the detent plate; also look for loose or corroded
rivets
Ü For gladhands with dust flaps, replace when
flaps are missing or show signs of wear
Ü For gladhands with filter screens, replace when
screens are damaged or congested with debris
Ü Regularly inspect rubber seals and replace
them immediately when showing signs of wear
"Replacing gladhands every time you replace
your air lines is another best practice," Mead adds.

Compressor issues and
oil in the system
Oil in the air system can present another set of
challenges. According to Expello Air's Johnson,
the compressor can be a major problem if not
well-maintained.

» The Expello Air Automatic Drain Valve
replaces the manual drain petcock on a
tank and helps to purge water, oil, and
dirt from the air tanks automatically.
Photo courtesy of Expello Air

» Air brake system valves are sensitive
to dirt, debris, and rust. One simple
preventive measure is to specify a trailer
brake in-line filtration system with an
easy-to-change cartridge that traps
debris before it can cause brake damage.
Pictured is the Air-Defense
System with Quick-Change
Cartridge from Phillips
Industries.
Photo courtesy of
Phillips Industries

"Failing
compressors
will add oil to
the air," Johnson
points out. "This will
foul the desiccant bed of the air dryer,
allowing excess water and oil to enter the
wet tank. If the wet tank is not drained
daily, that water and oil can end up entering the rest of the air system."
Johnson says an excessive amount of oil in the
wet tank discharge indicates a problem with the
compressor that should be addressed immediately. The key word is "excessive."
"Fleets need to look at the air compressor and
realize that all compressors, even brand-new ones,
will pass some oil," Bendix's Nagel says. "If enough
oil is passing, and when subjected to elevated
temperatures, fleets can end up with significant
carbon buildup at the discharge line - maybe
enough that air will not pass."
Given that longstanding challenge, air systems
have been built to tolerate a certain amount of oil.
Today's controls, however, don't have the same
tolerance levels. Nagel says this is one reason why
oil-coalescing filters are becoming more popular.
Another reason is the increasing use of AMTs.
"Most modern trucks with an AMT have an
air dryer with an oil-coalescing filter," Nagel
says. "This is a big change from a few years ago.
Fleets must maintain air dryer cartridges just
like they have been. But they must understand
that if a dryer is equipped with an oil-coalescing
cartridge, they need to replace it with an oil-coalescing cartridge."
To properly diagnose and resolve compressor/
oil issues, fleets can look at a few key areas. Oil on
the outside of the compressor could simply trace
back to leaky gaskets, lines, or fittings that need
to be adjusted, or perhaps replaced. When it is
evident that oil is leaking from the compressor
itself, a bigger problem could be at hand. Ideally,
a simple fix such as resealing the bottom cover
plate could solve this. Worst case, the compressor
needs to be replaced.
Excessive oil consumption can be a telltale
sign of a faulty compressor. However, TMC
Recommended Practice (RP) 630 says a host of
other problems could also be the culprit:
Ü Restricted air intake
Ü Poorly filtered air inlet
Ü Restricted oil return to engine
Ü Insufficient coolant flow
Ü Contaminants not being regularly drained from
system reservoirs

August 2019 | VehicleServicePros.com

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Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance