LINES GP-CONNECTING 3879690 - Caterpillar

Illustration 1 g06265532
Pressure Protection Valve
(1) Supply passage
(2) Valve
(3) Delivery passage
Illustration 2 g01000167
View of the inside left frame rail 777D Series Off-Highway Truck
Location of Pressure Protection Valve for the brake air system
Illustration 3 g06088993
View of the inside left frame rail 777E Series Off-Highway Truck
Location of Pressure Protection Valve for the brake air system
The Pressure Protection Valve is on the inboard side of the frame on the left side of the truck.The Pressure Protection Valve prevents complete loss of air pressure in the event of a failure in the secondary air system or any accessory device.All air flow from the Primary Air circuit to the Secondary Air circuit flows through the Pressure Protection Valve. Air will not flow through the Pressure Protection Valve until the air pressure at supply passage (1) reaches the valve opening pressure. When the air pressure reaches the valve opening pressure, valve (2) moves to allow air to flow through the Pressure Protection Valve to delivery passage (3). The Pressure Protection Valve closes when the air pressure reaches the valve closing pressure.For specific values of the valve opening pressure and the valve closing pressure, refer to Specifications, "Pressure Protection Valve (Brake Air System)" for the Air System and Brakes.