| ... |
|
Air Bag Control Valve |
|
Controls the inflation and deflation of
trailer air suspension bags. There are three basic modes for air bag
control:
1. A manual system which requires the user to operate the valve
to inflate or deflate the bags.
2. An semi-automatic system which the
user must trigger the deflation but will automatically inflate the bags when
the trailer park brakes are released.
3. A fully automatic system where
both the inflation and deflation functions are performed based on the trailers
park mode. |
| ... |
|
Anti-Lock Brake System
(ABS) |
|
On air brake trailers ABS is
defined by 49CFR 571.121 (FMVSS 121)
| Anti-lock brake system or ABS
means a portion of a service brake system that automatically controls the
degree of rotational wheel slip during braking by: |
| (1) |
Sensing the rate of angular rotation of
the wheels; |
| (2) |
Transmitting signals regarding the rate of
wheel angular rotation to one or more controlling devices which interpret those
signals and generate responsive controlling output signals; and |
| (3) |
Transmitting those controlling signals to
one or more modulators which adjust brake actuating forces in response to those
signals. |
|
| ... |
|
Brake Chambers |
|
There are two primary types of brake
chambers commonly used in air brake systems. One is called a spring brake
chamber. This is actually two chambers sometimes called a "piggyback". One
chamber operates the service brakes when the driver depresses the brake pedal
or hand valve. The second chamber contains a very large and powerful spring.
This spring is used to engage the brakes when the trailer is parked or in a
break away situation.
The second type of commonly used chamber is a
service only chamber. It is like a spring brake chamber minus the spring
section. It depends on the service valve to provide air pressure for brake
force during service application, park and/or emergency modes.
Air
systems (and the valves) must be designed specifically for each chamber type to
accommodate stopping, park and emergency requirements. The Technical Section contains more information
regarding the different systems. |
| ... |
|
Service Brake
Application Time |
|
| Elapsed time between the depression of the
brake treadle and the delivery of 60 psi to all of the service chambers per US
Regulations FMVSS 121 (49CFR 571.121). |
| ... |
|
Charging Style System |
|
| An air system where the reservoir(s) is
filled through a relay emergency valve (REV), not through a
pressure protection valve (PPV). When the supply line is "charged" with air,
the air enters the port marked "Emerg-Supply" of the REV through a one-way
check valve (an integral part of the REV) and into the reservoir(s) via the
reservoir port of the REV. |
| ... |
|
Check Valves |
|
One-way check valves allow air to flow in
only one direction, often protecting the air supply in a reservoir.
Two-way
check valves have two inlets and one outlet allowing airflow from the highest
pressure input only thereby blocking airflow from the lower pressure
inlet.
A Bypass check valve is special valve that allows full flow air
in one direction and a much smaller flow in the opposite direction. |
| ... |
|
Control Line or
Booster Valves |
|
| These valves are designed to boost and
accelerate the control signal for trailers with slow brake systems or low
timing thresholds. In addition they can substantially reduce release timing.
They are common on very long trailers, large multiple axle trailers, and
trailers or dollies designed to tow other trailers. The Dolly
Control Line Valve is of similar design and function. |
| ... |
|
Compounding/Anti-Compounding Feature |
|
'Compounding' is the simultaneous actuation
of both the spring (emergency) and service brakes. Compounding can result in
over-torque of the foundation brakes causing problems such as bent chamber push
rods, broken camshafts, cracked drums, lining damage, damaged chamber brackets,
etc.
Anti-compounding is a feature that prevents compounding and is
included in all current Sealco spring brake control valves. |
| ... |
|
Control or Service
Line |
|
| The air lines in the trailer air brake
system that control the variable strength braking of the vehicle from the
tractor foot valve or hand valve. Control or service lines are commonly
associated as the blue air line in a braking system. 'Control' is a post FMVSS
121 term and 'Service' is a pre FMVSS 121 term. |
| ... |
|
Charging Style Relay
Emergency Valve |
|
| A charging style relay
emergency valve (REV) fills the system reservoirs direct from the supply
line without the benefit of a pressure protection valve.
When the supply line is pressurized air enters the
"Emerg/Supply" port, through a one-way check valve (an integral part of the
REV) and into the reservoir(s). Because the supply line is not protected a
single failure in the system can lower the supply line pressure to critical
levels. A 1992 change in US law (49CFR 571.121) dramatically reduced the
applications in which a charging valve can be used. |
| ... |
|
Charging Style Relay
Emergency Valve |
|
| A charging style relay
emergency valve fills the system reservoirs direct from the supply line
without the benefit of a pressure protection valve. When the supply line is pressurized air enters the "Emerg/Supply"
port, through a one-way check valve (an integral part of the REV) and into the
reservoir(s). Because the supply line is not protected a single failure in the
system can lower the supply line pressure to critical levels. A 1992 change in
US law (49CFR 571.121) dramatically reduced the applications in which a
charging valve can be used. |
| ... |
|
Crack or Cracking
Pressure |
|
| The minimum amount of control air pressure
(in psi) required before an air valve will deliver. |
| ... |
|
Dolly Control Line Valves
(DCLV) |
|
| Similar to a standard Control Line
Valve with the addition of a port marked "Dolly Port" which applies and
releases the control line signal of air to the relay valve on the steerable
axle. The unmarked delivery port of the DCLV applies and releases the control
line signal of air to the downstream service relay valves. Commonly used on
converter dollies and turntable axles on pull, transfer and train-type
trailers. |
| ... |
|
Emergency Control Valve |
|
| Fills the reservoir(s) with air and takes the
service chambers in and out of emergency working with a Service
Relay or ABS relay valve. Commonly used on converter
dollies, turnable axles and trailers exempt from spring brakes. |
| ... |
|
False Charging |
|
| The phenomenon where pressurized air
(usually from the control line) enters the supply line of a parked trailer set
and releases the parking brakes. Generally the gladhand shut-off valve must be
shut off for this to happen. |
| ... |
|
Line Filters |
|
Supply Line Filters reduce the amount of
supply line contamination when used in the trailer supply line ahead of the
SBCV or REV thereby extending the useful life of other air valves in the
system.
Control Line Filters reduce the amount of the contamination
entering the control line. They include a bypass feature in case of clog and
generally have a smaller filter areas than a supply line filter. |
| ... |
|
Non-Charging Type
Relay Emergency Valve |
|
| A non-charging style relay
emergency valve fills the system reservoirs from the supply line through a pressure protection valve. Because the supply
line is protected in most failure modes the system will maintain the supply
pressure at or above 70 psi. Non-charging systems are required on most vehicles
manufactured after 1992 with service only brake chambers. |
| ... |
|
Pilot Port |
|
| A port on a valve generally used to change
the operational mode of the valve (Ex: Open to Closed). |
| ... |
|
Pressure Protection
Valve |
|
| Theses valves protect the upstream air
source in the event of a downstream failure. They are used to protect
reservoirs and supply lines from brake system and/or accessory failure. When
pressure drops sufficiently the valve will close to retain upstream air
pressure above the specified setting. |
| ... |
|
Protected Reservoir
System |
|
| A spring brake control valve (SBCV) option
using integral one-way check valves for two reservoir systems that assures the
loss of one reservoir will "protect" the other reservoir. Allows for the
release of the parking brakes at least once after they have been applied due to
the catastrophic loss of air pressure in one of the reservoirs. Simultaneously
charges the reservoirs and releases the parking brakes when starting with 0 psi
in the trailer air brake system. |
| ... |
|
Ratio Feature |
|
The Ratio Feature is considered a benefit
in hard stop situations & refers to the relationship between the control
air pressure to the valve & the delivered air pressure from the valve to
the service brake chambers.
During normal stopping a 1:1 ratio exists
between the control & delivered air pressures. In a hard stop the ratio
momentarily changes to 1:1.5 until valve lap-off occurs and the 1:1 ratio is
restored. This change takes place in less then 1/100th of a second.
The
preferred application for valves with this feature is controlling tandem
axles..
| Valves with a ratio feature should not be used on
converter dollies, lift axles or trailer turnable axles!. |
|
| ... |
|
Relay Emergency
Valve |
|
| A Relay Emergency Valve are used on vehicle
axles with service chambers only. They are designed to fill the reservoir(s),
apply and releases the service brakes, and apply and releases emergency/park
brakes when necessary. They are commonly used only on converter dollies,
trailer turntable axles and liftable axles. They come in 'Charging' and 'Non-Charging' designs. |
| ... |
|
Service Reservoir
Priority |
|
| A spring brake control valve (SBCV) option
where priority is given to directing supply air to fill the reservoir(s)
instead of releasing the spring brakes, even though both are building pressure
simultaneously. This priority prevents releasing the parking brakes after they
have been applied due to a catastrophic loss of air in the reservoir(s). |
| ... |
|
Spring Brake
Priority |
|
| A spring brake control
valve (SBCV) option where priority is given to releasing the parking brakes
instead of filling the reservoir(s). When supply line is
charged with air with 0 psi in the reservoir(s), it is sent directly to the
parking brakes. As the supply line pressure exceeds 80 psi, the pressure
protection valve (PPV) in the SBCV opens and fills the reservoir. This priority
allows for the release of the parking brakes after they have been applied due
to a catastrophic loss of air pressure in the reservoir(s). |
| ... |
|
Suspension Dump
Valve |
|
| Controls the inflation and deflation of
the trailer's air suspension system. There are manual versions and auto-reset
versions. The auto-reset version will refill the suspension when ever the
trailer park brakes are released. The manual versions allow the trailer to be
moved with the suspension pressure dumped. |
| ... |
|
Service Brake or
Service Reservoir Priority |
|
| A spring brake control
valve option where priority is given to directing supply air to fill the
reservoir(s) instead of releasing the spring brakes, even though both are
building pressure simultaneously. This priority prevents releasing the parking
brakes after they have been applied due to a catastrophic loss of air in the
reservoir(s). |
| ... |
|
Service Brake Release
Time |
|
| Elapsed time required to
reduce the pressure in all service chambers from 95 psi to 5 psi as per US
Regulations FMVSS 121 (49CFR 571.121). |
| ... |
|
Service Relay
Valve |
|
| Relays air from the reservoir to the brake
chambers performing the normal braking function upon receiving a signal from
the foot valve, hand valve or control line valve (CLV). Used
on post FMVSS 121 trailers with spring brake chambers |
| ... |
|
Spring Brake Relay
Feature |
|
| A spring brake control valve (SBCV) option uses trailer pressure to release the
spring brakes rather than the tractor filling the chambers via the supply line. This feature can
dramatically shorten the time a driver waits for the parking brakes to release. |
| ... |
|
Spring Brake Control
Valve |
|
| A valve that charges the trailer
reservoir(s) with air, applies & releases the parking brakes and applies
the emergency brakes if a catastrophic loss of supply line pressure occurs.
Determines the priority of air delivery when supply line air
is applied based upon the design of the SBCV (see Protected
Reservoir System, Spring Brake Priority & Service Reservoir Priority). Used on post FMVSS 121 trailers
with spring brake chambers, SBCVs combine a quick release valve (QRV), pressure
protection valve (PPV) and, in all Sealco SBCVs, a one-way check valve (CV) for anti-compounding. |
| ... |
|
Supply or Emergency
Line |
|
| The air lines in the trailer air brake
system that charge the trailer air reservoir(s) and apply and release the
parking or emergency brakes using the trailer push-pull valve in the tractor.
Supply or emergency lines are commonly associated with the red air line
function of the air system. 'Supply' is a post FMVSS 121 term and 'Emergency'
is a pre-FMVSS 121 term. |