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26 Cards in this Set
- Front
- Back
Spring brake chambers apply and hold a parking brake application |
Without air pressure |
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Caution must be exercised when working around spring brake equipped vehicles because |
Spring brakes contain large powerful springs |
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Air supply for parking/emergency brake operation flows through a double check valve so that the emergency brakes will |
Not apply if either service reservoir air pressure is lost |
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The function of the park control valve is to provide manual |
And automatic control of all the parking/emergency brake on the unit |
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A quick release valve is often used in parking/emergency brake circuits to provide quick |
Application of the spring brakes |
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An anti-compounding double check valve is often used in parking/emergency brake circuits to |
Release the parking/emergency brakes when the service brakes are applied |
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Some truck/tractor units are equipped with a spring brake valve that |
Allows modulated application of the spring brakes if primary derive reservoir air pressure is lost |
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A relay valve is used in parking/emergency brake circuits that use spring brake valves to ensure that the spring brakes |
Apply and release quickly |
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The purpose of the trailer supply line is to transmit air pressure |
To charge the trailer reservoirs |
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The purpose of the trailer service line is to transmit air pressure |
To apply and release trailer service brakes |
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The trailer supply valve supplies air pressure to the trailer from |
Both the primary and secondary reservoirs |
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In the event that pressure in both primary and secondary reservoirs falls below 50psi the |
Trailer supply valve will close off supply air pressure to the trailer Trailer emergency brakes will apply Tractor protection valve will close the trailer service line |
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The purpose of the trailer brake control valve is to allow the operator to |
Independently control trailer service brakes |
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If the operator makes a 20psi application with the trailer brake control valve while making a 10psi application with the dual-circuit brake valve |
Tractor brakes will be applied with 10psi and trailer brakes are applied with 20psi |
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Tractors equipped with a bobtail proportioning relay valve will reduce |
Primary application pressure when the tractor is not towing a trailer |
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The brake light switch is normally |
Open switch that is closed by primary or secondary service pressure |
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The purpose of the primary service circuit is to allow the operator to control the application and release of the ____ axle brakes |
Drive |
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The ______ valve in an air brake system gives the operator control of all the service brakes on the vehicle |
Dual-circuit brake |
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The dual circuit brake valve in the apply position will be applying the secondary brakes. Air pressure from the primary delivery port also flows through the ____ onto the top of the secondary piston |
Orifice |
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The relay valve is installed in the brake system to control ____ |
Brake lag |
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The relay valve, located near the primary brake chambers in the primary brake circuit, speeds up ____ and _____ time of drive axle brakes |
Application and release |
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When the operator depresses the treadle of the dual circuit brake valve, air pressure is sent to the ______ port of the relay valve and applies force to the upper surface of the ______ |
Control Relay piston |
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The amount of air that is required to get the relay valve piston to move downwards, close the exhaust valve and open the inlet valve is called |
Cracking pressure |
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A type 30 brake chamber indicates that the chamber has a diaphragm are of |
30in squared |
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The purpose of the secondary service circuit is to allow the operator to control the application and release of ____ axle brakes |
Steer |
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The function of a ______ valve is to provide a faster brake release by allowing the air in the brake chambers to exhaust at a location closer to the steer axle than the dual circuit brake valve |
Quick release |