PAD AS 2152891 - Caterpillar

Illustration 1 g00292672
Illustration 2 g00292709
(1) Left side steering cylinder. (2) Right side steering cylinder. (3) Shuttle valve. (4) Secondary steering diverter valve. (5) Secondary steering pump. (6) Crossover relief valves. (7) Steering control valve. (8) Damper for the steering control valve. (9) Oil coolers for the steering and brake systems. (10) Bypass check valve for the steering and brake oil coolers. (11) Steering and brake oil filter. (12) Fluid sampling valve. (13) Left neutralizer valve. (14) Right neutralizer valve. (15) Pressure and flow compensator valves. (16) Check valves. (17) Steering pump. (18) Small actuator piston. (19) Large actuator piston. (20) Steering pump. (21) Steering and brake oil cooler pump. (22) Steering metering pump. (23) Pressure reducing valve. (24) Check valve. (25) Pressure switch for the steering oil. (26) Pressure reducing valve. (27) Return screens. (28) Hydraulic tank for the steering and brake systems. (A) Pressure tap for the rod end of the left side cylinder. (B) Pressure tap for the rod end of the right side cylinder. (C) Pressure tap for the head end of the left side steering cylinder. (D) Pressure tap for the head end of the right side cylinder. (E) Pressure test point for the cooler outlet. (F) Pressure test point for the cooler inlet. (G) Pressure test point for the steering pump. (H) Pressure test point for the steering pump.The system can be divided into two parts, the pilot system and the steering system.Pilot System
The pilot system controls the movement of the spool in steering control valve (7) . The pilot system includes the following main components: right neutralizer valve (14), left neutralizer valve (13) and steering metering pump (22) .Steering pump (20) supplies a constant source of pressure oil to pressure reducing valve (26) . Pressure reducing valve (26) reduces the pump pressure oil to pilot pressure oil. Pilot oil flows from pressure reducing valve (26) through an orifice to steering oil pressure switch (25) . The orifice reduces the amount of false pressure indications which can be caused by pressure spikes in the system. Steering oil pressure switch (25) alerts the operator if the pilot oil pressure drops off below 700 103 kPa (100 15 psi) .The arrangement of pressure reducing valves (23) and (26) isolates steering oil pressure switch (25) from the rest of the steering system. This prevents any secondary steering oil pressure from deactivating steering oil pressure switch (25) .The return oil flows from pressure reducing valves (23) and (26) through return screens (27) and back to hydraulic tank (28) . Any oil that may leak past the valve spool in pressure reducing valves (23) and (26) also flows back to hydraulic tank (28) .Steering metering pump (22) is a small