PLATE 2741771 - Caterpillar

Illustration 1 g03383110
Cross section of straight travel control valve and main relief valve
(1) Straight travel control valve
(2) Main control valve
(3) Right travel control valve
(4) Check valve
(5) Check valve
(6) Main relief valve
(7) Delivery line (idler pump)
(8) Delivery line (drive pump)
(9) Idler pump
(10) Drive pump
(11) Internal passage Main relief valve (6) is located in the left side of the main control valve. The main relief valve 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 drive pump (10) enters main control valve (2) through delivery line (8). The oil delivery from idler pump (9) enters main control valve (2) through delivery line (7). Drive pump oil and idler pump oil flows through check valves (4) and (5) to passage (11). Check valves (4) and (5) ensure that only the higher oil pressure from the drive pump or the idler pump flows through passage (11) to main relief valve (6).Closed Position
Illustration 2 g03384406
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