BODY 1105157 - Caterpillar

Illustration 1 g03877984
View of left control valve
(1) Main relief valve
(2) Inlet manifold
(3) Return passage
(4) Supply port
(5) Inlet passage Each main control valve has a main relief valve. The main relief valve is located in inlet manifold (2) which is bolted on top of each control valve.The main relief valve limits the oil pressure from supply port (4) to the implement hydraulic system through inlet passage (5) from the implement pumps. When the pressure at the inlet of the main control valve exceeds the pressure setting of main relief valve (1), the main relief valve opens. The excess hydraulic oil then flows through main relief valve (1) to the hydraulic oil tank through return passage (3).Closed Position
Illustration 2 g03878013
Main relief valve (closed position)
(1) Adjustment screw
(2) Locknut
(3) Spring
(4) Poppet
(5) Valve chamber
(6) Seat
(7) Spring chamber
(8) Spring
(9) Seat
(10) Valve
(11) Passage
(12) Orifice
(13) Passage
(14) Return passage
(15) Passage Poppet (4) is positioned to the right against seat (6) by the force of spring (3). Valve (10) is positioned to the right against seat (9) by the force of spring (8).System oil pressure in passage (11) flows through orifice (12) into spring chamber (7). The force of the system pressure oil acts on poppet (4). When the force of system pressure oil in passage (11) is less than the force of spring (3), poppet (4) remains against seat (6). The pressure in passage (11) and the pressure in spring chamber (7) are now equal. System pressure oil in spring chamber (7) and the force of spring (8) maintain valve (10) against seat (9). There is no oil flow from passage (11) to return passage (14). When implement pump oil pressure in passage (11) is less than the main relief pressure setting, the main relief valve remains in the closed position.Open Position
Illustration 3 g03878090
Main relief valve (open position)
(1) Adjustment screw
(2) Locknut
(3) Spring
(4) Poppet
(5) Valve chamber
(6) Seat
(7) Spring chamber
(8) Spring
(9) Seat
(10) Valve
(11) Passage
(12) Orifice
(13) Passage
(14) Return passage
(15) Passage System oil pressure in passage (11) and spring chamber (7) nears the main relief valve pressure setting. The force of the system oil pressure in spring chamber (7) becomes greater than the force of spring (3). Poppet (4) moves away from seat (6). System oil pressure now flows through seat (6) into valve chamber (5). The oil in valve chamber (5) now flows through passage (15) into return passage (14). This low-pressure oil now returns to the hydraulic oil tank.At the same time as the oil in spring chamber (7) flows through seat (6), the system pressure oil in passage (11) flows through orifice (12). As the system oil pressure flows through orifice (12) into spring chamber (7) the pressure of the oil in spring chamber (7) decreases. The reduced pressure oil in spring chamber (7) allows the high-pressure oil in passage (11) to force valve (10) away from seat (9). The high-pressure oil in passage (11) now flows into passage (13) and return passage (14) to the hydraulic oil tank.The amount of spring force of spring (3) that acts on poppet (4)