Ch35 Servicing Air Brake Air
Systems Exam Questions with
Answers
Safety relief valve, p919 - - Releases air if tank pressure goes above 150 psi.
- Manual reservoir drain valve, p919, 921 - -
- Automatic reservoir drain valve, p919, 921 - -
- Single check valve, p1791, 92 - - A wet tank has a second valve (a one-
way check valve located between service thank and primary or secondary
tank). This valve prevents air from leaking back from either the primary or
secondary tank if there is a failure causing the wet tank to lose air.
- Foot (treadle) valve, p927-30 - - Foot (treadle) valve, p927-30, - Center of
the delivery system - It distributes air to the brake chambers and controls
the air pressure supplied for braking. When the driver operator depresses the
brake pedal, the foot valve delivers air pressure proportional to pedal travel.
The more the driver depresses, the more air pressure is given to the brake
chambers.
- Quick-Release Valve, p939 - - This valve is designed to speed up the
exhaust of air from brake chambers and other air valves. If the valve didn't
exist, air would flow back to the foot valve, causing too much pressure in the
system and not release brake chambers. Common QR valves have 3 ports, a
supply port located at the top and two delivery ports on the sides.
- Relay Valve, p930-33, 34, 36 - - Air relay valves use a small amount of air
to control, signal or switch larger volumes of air flow. These are critical
devices used to speed the flow and increase of air volume supplied to brake
chambers during braking applications and release.
- Park Control Valve (Yellow push-pull valve), p939, 40 - - The button is
pushed in to release the truck spring brakes and pulled out for parking.
Pulling the valve button out exhausts air from the air signal port connected
to the spring brake relay valve.
- Trailer Supply Valve (red octagonal push-pull valve), p944 - - The trailer
supply valve is depressed to supply air to the trailer to release its spring
brakes. It is used to control the TP system and route air from the secondary
brake reservoir to the trailer brake reservoir.
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