SEAL-LIP TYPE 3577435 - Caterpillar

Illustration 1 g06143382
Partial hydraulic schematic for the return system
(1) Travel motor
(2) Swing motor
(3) Drain line
(4) Main control valve
(5) Swivel
(6) Drain line
(7) Makeup line
(8) Drain line
(9) Valve
(10) Center bypass passage
(11) Return passage
(12) Center bypass passage
(13) Valve
(14) Drain line
(15) Orifice
(16) Orifice
(17) Drain line
(18) Pilot manifold
(19) Pilot oil distribution manifold
(20) Drain line
(21) Return line
(22) Return block
(23) Return passage
(24) Boom priority valve
(25) Hydraulic oil cooler
(26) Bypass check valve
(27) Slow return check valve
(28) Boom regeneration PRV
(29) Drain line
(30) Return line
(31) Hydraulic tank
(32) Suction line
(33) Case drain filter
(34) Drain line
(35) Idler pump
(36) Pilot pump
(37) Drive pump
(38) Drain line
(39) Negative flow control valveThe oil from drive pump (37) and idler pump (35) enters main control valve (4). Then, the oil flows to the return passages in one of the following conditions.
When all joysticks and/or travel levers/pedals are in the NEUTRAL position, oil from idler pump (35) flows through center bypass passage (10) through orifice (16) to return passage (23). Oil from drive pump (37) flows through center bypass passage (12) through orifice (15) to return passage (23).
When any one of the joysticks and/or travel levers/pedals is shifted from the NEUTRAL position, center bypass passages (10) and (12) are blocked. The return oil from the cylinders and/or motors now flows through return passage (11).
Illustration 2 g02760162
Return system components
(1) Travel motor
(3) Drain line
(4) Main control valve
(8) Drain line
(21) Return line
(25) Hydraulic oil cooler
(26) Bypass check valve
(27) Slow return check valve
(31) Hydraulic tank
(32) Suction line
(33) Case drain filter
(35) Idler pump
(36) Pilot pump
(37) Drive pump
(38) Drain line
(39) Negative flow control valveThe return oil from return passage (23) and return passage (11) flows through slow return check valve (27) back to hydraulic tank (31) in one of the following conditions.
When the oil temperature is very low, most of the oil is returned through bypass check valve (26) to hydraulic tank (31). The remainder of the oil flows into hydraulic oil cooler (25) and to hydraulic tank (31).
When the oil temperature increases, the rate of oil flow through bypass check valve (26) decreases. This action causes the rate of oil flow through hydraulic oil cooler (25) to increase.Case drain oil from drive pump (37) and idler pump (35) flows into case drain line (38).Reference: For more information concerning the bypass check valve, refer to Systems Operation, "Bypass Valve (Return)".
Illustration 3 g02683236
Return system components
(2) Swing motor
(4) Main control valve
(5) Swivel
(6) Drain line
(7) Makeup line
(8) Drain line
(14) Drain line
(18) Pilot manifold
(20) Drain line
(22) Return block
(24) Boom priority valve
(28) Boom regeneration PRV
(29) Drain line
(30) Return line
(31) Hydraulic tankCase drain oil from the left travel motor and case drain oil from the right travel motor combine and flow through swivel (5). From swivel (5) the case drain oil combines with the case drain oil from swing motor (2). Case drain oil in line (6) from the swing motor and case drain oil from the travel motors flows into drain line (8). Oil flow from drain line (8) combines with case drain line (38) from the pumps. All of the case drain oil from the pumps and the motors