HOSE AS 2Q7273 - Caterpillar

Illustration 1 g01038321
Main control valve
(A) Location of the main relief valveThe main relief valve is on the inlet section of the main control valve. The main control valve is located in the front frame. The main relief valve limits the pressure from the implement pump to the main hydraulic system.
Illustration 2 g06002657
Section view of the main relief valve
(1) Inlet
(2) Valve
(3) Outlets
(4) Passage
(5) Spring
(6) Seat
(7) Valve
(8) SpringHydraulic oil flows into inlet (1), through the orifice in the center of valve (2), and into the chamber for spring (5). The oil in the spring chamber contacts valve (7). Seat (6) cannot move. Seat (6) is pressed into the valve body.When the pressure of the oil in the circuit is less than the relief valve setting, the force of spring (8) on valve (7) keeps the main relief valve closed.If the oil pressure in inlet (1) exceeds the relief valve setting, the oil pressure overcomes the force of spring (8). This causes valve (7) to open. The oil in the chamber for spring (5) flows through the hole in seat (6). The oil then flows through passage (4) to the hydraulic tank.When valve (7) opens, the pressure of the oil in the chamber for spring (5) decreases. The pressure of the oil at inlet (1) causes valve (2) to open. Oil can then flow through outlets (3), and return to the hydraulic tank.Valve (2) remains open until valve (7) closes. Valve (7) will close when the pressure at inlet (1) decreases below the pressure setting of the relief valve.