GEAR GP-OUTPUT TRANSFER 8P2186 - Caterpillar

Illustration 1 g02980956The pilot relief valve is mounted on the rear frame cross beam.
Illustration 2 g01018678
(1) Pilot relief valve
(2) Inlet
(3) Seat
(4) Valve
(5) Spring
(6) Outlet
(7) Valve
(8) Passage
(9) Spring Relief Operation
Hydraulic oil flows into inlet (2) through the orifice in the center of valve (7) and then into the chamber for spring (9). The oil in the spring chamber contacts valve (4). Seat (3) cannot move, seat (3) is pressed into the valve body.When the pressure of the oil in the pilot circuit is less than the relief valve setting, the force of spring (5) on valve (4) keeps the relief valve closed.If the pressure oil in inlet (2) exceeds the relief valve setting, the pressure oil overcomes the force of spring (5). This causes valve (4) to open. The oil in the chamber for spring (9) flows through the hole in seat (3). The oil then flows through passage (8) to the hydraulic tank.When valve (4) opens, the pressure of the oil in the chamber for spring (9) decreases. The pressure of the oil at inlet (2) causes valve (7) to open. Oil can then flow through outlet (6) and return to the hydraulic tank.Valve (7) remains open until valve (4) closes. Valve (4) will close when the pressure at inlet (2) decreases below the pressure setting of the relief valve.