PUMP 1R9816 - Caterpillar

Limitation Of Pressure In Circuit
Two types of relief valves are installed on the main control valves in order to limit the pressure in the hydraulic circuit.
The main relief valve limits the pressure in the main hydraulic system.
The line relief valve limits the pressure which is built into the cylinder circuits.Main Relief Valve
Illustration 1 g02131076
Straight travel control valve and main relief valve (sectional view) (1) Main control valve (2) Right travel control valve (3) Line (4) Heavy lift solenoid valve (5) Straight travel control valve (6) Check valve (7) Check valve (8) Passage (9) Main relief valve (10) Line (11) Passage (12) Pilot manifold (13) Pilot pump (14) Drive pump (15) Line (16) Idler pump (17) LineOil from drive pump (14) and idler pump (16) enters main control valve (1) through lines (10) and (17) . Drive pump oil and idler pump oil goes through check valves (7) and (6) to passage (8) . The higher oil pressure from the drive pump or the idler pump goes through passage (8) to main relief valve (9) . CLOSED Position (Heavy Lift OFF)
Illustration 2 g02023862
Main relief valve (CLOSED) (8) Passage (18) Valve (19) Spring chamber (20) Spring (21) Valve (22) Spring (23) Passage (24) Orifice (25) Return passageWhen main pump oil pressure in passage (8) is less than the main relief pressure setting, valve (18) and valve (21) is closed by the force of spring (20) and spring (22) . The oil in passage (8) goes through orifice (24) . Oil enters spring chamber (19) . The pressure in passage (8) and the pressure in spring chamber (19) are equal. Valve (18) shifts left by the force of spring (20) . Valve (18) closes passage (23) . There is no oil flow from passage (8) to return passage (25) . OPEN Position (Heavy Lift OFF)
Illustration 3 g02023877
Main relief valve (OPEN) (8) Passage (18) Valve (19) Spring chamber (20) Spring (21) Valve (22) Spring (23) Passage (24) Orifice (25) Return passage (26) Passage (27) ChamberOil pressure in passage (8) nears the relief pressure setting. Oil pressure in passage (8) overcomes the force of spring (22) . The oil pressure opens valve (21) . The oil in valve chamber (27) goes through passage (26) to return passage (25) . The oil is called low pressure oil. The oil pressure from passage (8) decreases at orifice (24) . The oil then goes through spring chamber (19) to valve chamber (27) . Because of the decreased oil pressure in spring chamber (19) , the oil pressure from passage (8) pushes valve (18) to the right against the force of spring (20) . Passage (23) now opens allowing the high pressure oil flow from passage (8) to return passage (25) .Heavy Lift Operation
Illustration 4 g02023876
(8) Passage (18) Valve (19) Spring chamber (20) Spring (21) Valve (22) Spring (23) Passage (24) Orifice (25) Return passage (26) Passage (27) Chamber (28) Piston (29) Passage (30) Port
Illustration 5 g02638163
Spft Switch Panel (right console) (31) Heavy lift switchWhen the heavy lift switch (31) is placed