SHEET AS 1385631 - Caterpillar

Illustration 1 g00296487
View of the Front End Frame (1) Line relief valve for the rod end of the tilt cylinder. (2) Line relief valve for the head end of the tilt cylinder.The line relief valves are located on the main control valve. The main control valve is mounted on the front end frame. There is a line relief valve for both the head end of the tilt cylinder, and for the rod end of the tilt cylinder.Note: For machines with auxiliary functions, the head end of the auxiliary cylinders and the rod end of the auxiliary cylinders also have a line relief valve.When the tilt valve spool is in the HOLD position, the line relief valves for the head end and the rod end of the tilt cylinder limit the maximum pressure in the tilt circuit.When the auxiliary valve spool is in the HOLD position, the line relief valves for the head end and the rod end of the auxiliary cylinders limit the maximum pressure in the auxiliary circuit.Note: The operation of all the line relief valves is similar. An explanation of a typical line relief valve is given.
Illustration 2 g00296489
Line Relief Valve (3) Inlet. (4) Valve. (5) Passage. (6) Orifice. (7) Passage. (8) Plate. (9) Spring.Any outside force on the bucket or the auxiliary cylinders will increase the oil pressure in inlet (3). If the oil pressure against valve (4) exceeds the force of spring (9), valve (4) will move down.Oil then flows through passage (5) to the hydraulic oil tank. The pressure in inlet (3) is reduced in order to prevent damage to the components of the cylinder circuits.When a line relief valve opens, the tilt cylinder or the auxiliary cylinder slowly moves. Makeup oil flows through passage (7) and into the hole in plate (8). The oil then flows through orifice (6), and through passage (5) to the rod end or the head end of the cylinder.Reference: For more information on the pressure setting of the line relief valves, refer to the Service Manual module for Specifications, "Relief Valve (Line)" for the machine that is being serviced.Reference: For more information on adjusting the pressure setting of the line relief valves, refer to the Service Manual module for Testing and Adjusting, "Relief Valve (Line) - Test and Adjust" for the machine that is being serviced.