[TITLE: HOW THE AIR DRYER WORK TO PASS YOUR CDL AIR BRAKE PRE-TRIP INSPECTION TEST]
Hi there smart drivers Rick with Smart Drive Test
talking to you today about air brakes
and specifically the air dryer. I had a
comment from Mike9889 and noah arce,
both of them wanted a bit more
information about the air dryer. The air
dryer on all vehicles is located between
the compressor and the first air tank,
whether that's the supply tank or if
it's an ADIS--an Air Dryer Integrated System--
it will be located
between the air compressor and the two
tanks - the primary and secondary tank in
the system. In this day and age. all air
dryers look the same:
they look like a top hat. They can be
located pretty much anywhere on the
vehicle. I've seen them on the front of
the truck, underneath the cab, up
underneath the frame at the back of the
cab. So they're in different places on
the unit. Essentially all the air dryer does is clean
the air. These remove moisture and other
contaminants that are found in the air
after the air is compressed. And as well, the air dryer
prevents freezing in the system because it removes moisture. So today
we're going to give you a bit more
information about that. First, we're going to go
over the older systems that have supply
tanks (wet tank) and we're going to go over the new
modern air brake systems that have ADIS
systems--air dryer integrated systems--
which have made the wet tank redundant.
So stick around, we'll be right back with
that information.
[OPENING CREDITS & MUSIC]
Hi there smart drivers, welcome back. Rick with
Smart Drive Test talking to you today
about air brakes and specifically the
air dryer. The air dryer, simplistically
speaking, removes moisture and other
contaminants from the compressed air
before it enters the main airbrake
system. And by removing contaminants, it
prevents damage to the system and by
removing water it prevents or eliminates
the chance of that water
freezing in the main airbrake system and
causing it to fail during cold weather.
All air dryers are plumbed in to the system between
the compressor and the first tank. On
older systems that first tank is going
to be the wet tank. And it's called the
wet tank because the hot air that comes
out of the compressor goes into the wet
tank, it cools and the moisture inside of
the air comes in contact with the cold
metal of the tank, and the water inside
condenses. On older systems you needed a
wet tank because the air dryers were not
very efficient - you got a fair bit of
moisture and that moisture was collected
in the wet tank and drained and expelled
from the system before it could do
damage or potentially cause freezing in
the winter time. Now simply speaking,
air dryers are nothing more than a
filtration system. The air dryer itself
is filled with a desiccant and
essentially a dessicant is nothing more
than kitty litter. And the compressed air
under high pressure is forced through
the kitty litter and the kitty litter
collects the moisture and other contaminants that
are found in the compressed air. When the
system maintains maximum pressure--on
most systems that's going to be between
a hundred pounds and a hundred
thirty-five pounds--most systems in this
day and age you're gonna run run around
125 pounds per square inch mark. When the
airbrake system maintains maximum
pressure, the air dryer purges or expels
and it kicks out all the contaminants. So
if the the airbrake eqipped
vehicle has been sitting there running
for a while you'll begin to see a spot
on the ground - a bit of moisture and
whatnot.
If you see an excessive amount of
moisture that means there's something
wrong with the air dryer or compressor. For the most
part, you'll just see a bit of moisture
on the ground. As well, when the vehicle
is idling and you're walking by and goes PSSSSST [FEIGNING FRIGHT & LAUGHING]
and it scares the crap out of you - that's
the air dryer - and you know the system is
at maximum pressure because the air
dryer
purges at maximum pressure. So you'll
know what it is. And when you're doing
your in cab pre-trip inspection and
you're waiting for the system attain
maximum pressure, the first thing you're
going to hear is the air dryer. And as
many drivers' manual state: the air dryer
is not the only indicator that the
airbrake system is at maximum pressure.
Yes it is the first indicator, but you
must also look at the air gauges and confirm
that in fact the system is between a
100 psi and a 135 psi
to confirm that, in fact, the system is at maximum
pressure. But because we react to sound
first, we're going to hear the air dryer
purge. Some of the newer systems, the air
dryer is actually quiet, so you're
going to have to roll down your window and
listen for that air dryer purging to
know the system is a maximum pressure. So
older air brake systems are going to have a wet
tank. The air dryer is going to be
between the compressor and the wet tank.
It will purge at maximum pressure and it is a
filtration system that is filled with desiccant,
and as i said in the introduction, these
air dryers can be located in number of
places on the vehicles: on Freightliners,
they're up in the passenger corner, right
up underneath the engine compartment; on
Western Stars. I've seen them up
underneath the cab; and on an
International, I've seen them at the back
of the cab up underneath the frame. So
I've seen them in different locations
throughout the vehicle on different
makes and models. So you just have to
look around. Most of them in this day and
age are all going to be shaped like a
top hat. You can see a picture of one
here in the image, and you see that shape
and you know it's going to be the air
dryer. I have seen on some really, really
old trucks--1980s and 1990s--they are a
bit different shape, but for the most
part they're going to be the same shape.
It's easy to locate when you do your conducting your
pre-trip inspection - you just basically
look at them and say:
"there's no excessive amount of moisture
or water underneath the air dryer, and as
well, it's not cracked or damaged and
they don't have any leaks. So essentially
that's all you have to do for a pre-trip
inspection. And it will be the indicator
that the system is at maximum pressure
as I already went over. On an older
system you have a wet tank and for the
purposes of a pre-trip inspection, after
you secure the vehicle by chocking the
wheels and releasing the parking brakes,
you're going to drain the wet tank. And
the reason you drain the wet tank first
is to check to make sure that the 2
one-way check valves at the entrance to
the primary and secondary tank are
operating normally.
Because those two one-way check valves
are primarily responsible for the
division of the airbrake system into a
primary and secondary subsystem. So on
older systems that have a wet tank,
that's the first thing you're going to
have to do. And to locate the wet tank on
an older system, you go into the truck and
take note of what the air pressure is on
the gauges. Then you go out and start draining
tanks. The tank that doesn't drain the
gauges on the dash is your wet tank,
because the wet tank doesn't have a
gauge on it. Most modern air brake systems
all have ADIS systems - air dryer
integrated systems, which essentially
means that they have eliminated the wet
tank. So they don't have a wet tank.
There are two characteristics that will
tell you have an ADIS system.
The first characteristic is that
the governor will be within close
proximity of the air dryer, and you can
see that here in the image. That it's
right beside the air dryer. So that's
your first indication that you have an
ADIS system and don't have a wet tank.
The second indicator is that when you
pump up the system and build pressure in
the cab and you're watching the gauges,
one system will fill first, either the primary or
secondary, will build up to approximately one
hundred pounds and then the other system
will begin to pump up.
That's the other indicator that tells you
you have an ADIS system. Now if you have
an ADIS system, you don't have to drain
the wet tank obviously, because you don't
have a wet tank; however, when you do get
in the cab after doing your outside
pre-trip inspections you do need to take
note of the needles--the air pressure
needles--and tell the examiner that they
haven't dropped, which indicates that the
one-way check valves at the entrance of
the primary and secondary system are
working correctly, and that you more-or-
less know, for the most part. that the
division of the two secondary and primary
systems are working and functioning
normally.
So what we're going to do here is, I've
got access to a truck and we're just
going to go out and have a look at the
truck and I'll show you a little bit out
at the truck about a modern ADIS system.
So this truck is a newer model truck.
This truck has what is called an ADIS
system which is air dryer integrated
system and you can tell that it's an air
dryer integrated system because you can
see that the governor is right here
beside the air dryer. And that's your
indication that you have an
ADIS system. All an ADIS system means is
that the system does not have a wet tank
on it, only has a secondary and primary
tank. Essentially what happened is that
the air dryer is so effective that it's
made the wet tank redundant. And they no
longer use it. If you have an older
system, you're going to have to drain the
wet tank first during your pre-trip inspection. If you know you have an
ADIS system, the driving school will
teach you that - that you have an ADIS system
and you don't have to drain the wet tank -
you just indicate to the examiner that
you have an ADIS system. And that's
indicated by the fact that the governor
is right beside the air dryer. So
basically all you inspect here is the governor, the
air dryer is secure, not damaged, and not leaking.
All the lines, hoses, and wires are secure,
not damaged. And you can tell you have
airlines back here as well because you
have air suspension on the cab and
that's essentially what you inspect at
this juncture.
A quick review of air dryers on air brake
equipped vehicles. On all vehicles, the
air dryer is plumbed into the system
between the air compressor and the first
tanks. On an older system, that first tank
is going to be the wet tank; on a newer
system it's going to be the secondary
and primary tanks. As well, all the air
dryers are shaped the same - they look
like a top hat and they will be found in
different places on the vehicle,
depending on the make of the vehicle.
Some vehicles, it will be in the engine
compartment - up on the passenger side.
Other vehicles the air dryer will be up underneath the
cab, and on other ones the air dryer will be behind the
cab, bolted to the frame. The air
dryers is nothing more than a filtration
system that's filled with desiccant--
kitty litter--that the compressed air is
forced through. The disiccant removes
contaminants and moisture from the
compressed air. At maximum air pressure
of the air brake system it expels or
purges the contaminants and moisture out
onto the ground. And if the vehicle has been
sitting there idling for a while, you'll
see a bit of a moisture spot on the
ground. As well it is the first indicator
that you know that the airbrake system
is at maximum pressure, but it is not
the only indicator. And for some driving
test you can't use the air dryer purging
as the only indicator that the system is
at maximum pressure. When the system attains
maximum pressure, you say to the examiner: "I hear, I see..." So you
have to check the gauges and ensure that
the gauges are in fact at maximum pressure
between a hundred and hundred
thirty-five pounds per square inch. On
modern air brake systems, air dryers have
become so efficient in removing
contaminants and moisture from the air
in the air brake system that they have
made the wet tank redundant. And on
modern air brake systems we no longer
have wet tanks, however all the manuals
will tell you that you still need to
drain the air tanks daily, daily, daily,
even though there's very little moisture
in them - that's the answer to the
question on the test. Air dryers are very
effective and they are more or less a
standard feature of modern air brake
systems. Some of the drivers' manual will
tell you that they are optional -
they're not optional anymore. You'll find
them on every airbrake system and they
have been for decades on air brake
systems. Unfortunately, as I've stated in
previous videos--most jurisdictions--
there's two still teaching a
forty-year-old airbrake course, and that
is unfortunate because that needs to
be revisited. Question for my smart
drivers - where is the air dryer located
on your air brake equipped vehicle? Leave
a comment down in the comment section
there. All that helps out the new
drivers coming into the industry.
I'm Rick with Smart Drive Test, thanks
very much for watching. If you like what
you see here share, subscribe, leave a
comment down in the comment section. As
well, hit that thumbs up button. Check out all
the videos on the channel if you're
working towards a license or starting a
career as a truck or bus driver - lots of
great information here. As well, head or
website - lots of great information there.
Stick around to the end of the
video where there are links to other videos and great
information for you to be successful in
your endeavors of getting your license.
Thanks again for watching. Good luck on
your road test. And remember, pick the
best answer not necessarily the right
answer.
Have a great day. Bye now.
Wecome back, Rick with Smart
Drive Test talking today about air
brakes and specifically the air dryer.
The air dryer simplistically speakn'
speakn', speakn'... I'ssss speeeeaaakn'
[LAUGHING & WALKING OFF-CAMERA]
[CLOSING CREDITS & MUSIC]