CARRIAGE AS 1528405 - Caterpillar

Illustration 1 g03388727
Cross section of the main relief valves
(1) Main relief valve (rear pump)(stick and right travel)
(2) Main relief valve (front pump)(bucket, boom, and left travel)
(6) Hydraulic oil supply from the front pump
(7) Hydraulic oil supply from the rear pump
Illustration 2 g03388870
Partial schematic and cross section of the main relief valves
(1) Main relief valve (rear pump)(stick and right travel)
(2) Main relief valve (front pump)(bucket, boom, and left travel)
(3) Front pump
(4) Rear pump
(5) Main control valve center manifold
(6) Hydraulic oil supply from the front pump
(7) Hydraulic oil supply from the rear pump Main relief valve for front pump (bucket, boom, and left travel) (2) and main relief valve for the rear pump (stick and right travel) (1) are located in the center manifold of the main control valve. The main relief valves limits the maximum operating pressure of the travel hydraulic circuit and the implement hydraulic circuits when the machine is at a load condition.The oil delivery from front pump (3) enters main control valve center manifold (5) through delivery line (6). Front pump oil then acts on relief valve (2). Main relief valve (2) regulates the hydraulic operating pressure to the front pump circuits.The oil delivery from rear pump (4) enters main control valve center manifold (5) through delivery line (7). Rear pump oil then acts on relief valve (1). Main relief valve (1) regulates the hydraulic operating pressure to the rear pump circuits.Closed Position
Illustration 3 g03389287
Main relief valve (closed position)
(11) Passage
(12) Seat
(13) Valve
(14) Spring
(15) Spring chamber
(16) Seat
(17) Poppet
(18) Spring
(19) Passage
(20) Orifice
(21) Return passage Poppet (17) is positioned to the left against seat (16) by the force of spring (18). Valve (13) is positioned to the left against seat (12) by the force of spring (14).System pressure oil in passage (11) flows through orifice (20) into spring chamber (15). The force of the system pressure oil acts on poppet (17). When the force of system pressure oil in passage (11) is less than the force of spring (18), poppet (17) remains against seat (16). The pressure in passage (11) and the pressure in spring chamber (15) are now equal. System pressure oil in spring chamber (15) and the force of spring (14) maintain valve (13) against seat (12). There is no oil flow from passage (11) to return passage (21). When main pump oil pressure in passage (11) is less than the main relief pressure setting, main relief valve (6) remains in the closed position.Open Position
Illustration 4 g03389446
Main relief valve (open position)
(11) Passage
(12) Seat
(13) Valve
(14) Spring
(15) Spring chamber
(16) Seat
(17) Poppet
(18) Spring
(19) Passage
(20) Orifice
(21) Return passage
(22) Passage
(23) Valve chamber
(24) Locknut
(25) Adjustment screw System oil pressure in passage (11) and spring chamber (15) nears the main relief valve pressure setting. The force of the system oil pressure in spring chamber (15) becomes greater than the force of spring (18). Poppet (17) moves away from seat (16). System oil pressure now flows through seat (16) into valve chamber (23). The oil in valve chamber (23) now flows through passage (22) into return passage (21). This