TUBE-PLASTIC 1U8757 - Caterpillar

Attachment Valves (A1 and A2)
Illustration 1 g06213809
Attachment valves (A1 and A2) located in pump compartment (typical example)
Illustration 2 g06191521
Valve cutaway, hydraulic schematic symbol, and electrical connector designation
Note: The values in Table 1 are for bench testing only. Values may not represent parameters for machine systems specifications.
Table 1
Rated Voltage 12 VDC
Coil Resistance 8.15 0.4Ω (T=20° C)
Illustration 3 g06237029
A - Port pressure (kPa) vs Current (mA)
The proportional reducing valves electronically control the spool shift pressure for the attachment control valves. These valves make available of control of attachment control valve by electric control input or hydraulic control input. Operation of the work tool is enhanced because the spool shift pressure is controlled in accordance with operator control input.Attachment Valves (A3)
Illustration 4 g06213876
Attachment valves (A3) located in swing motor compartment (typical example)
Illustration 5 g02304193
Valve cutaway, hydraulic schematic symbol, and electrical connector designation
Note: The values in Table 2 are for bench testing only. Values may not represent parameters for machine systems specifications.
Table 2
Current Range 0 mA ~ 700 mA
Coil Resistance 15.0 0.5Ω (T=20° C)
Illustration 6 g02263554
A - Port pressure (kPa) vs Current (mA)
The proportional reducing valves electronically control the spool shift pressure for the attachment control valves. These valves make available of control of attachment control valve by electric control input or hydraulic control input. Operation of the work tool is enhanced because the spool shift pressure is controlled in accordance with operator control input.Variable Relief Valves
Illustration 7 g06213779
Variable relief valves located above the swing motor compartment (typical example)
Illustration 8 g02304476
Solenoid valve, hydraulic schematic symbol, and electrical connector designation
Note: The values in Table 3 are for bench testing only. Values may not represent parameters for machine systems specifications.
Table 3
Max Flow Rate 400 L/min
P-Port Pressure Range 980 kPa to 37700 kPa
Current Range 0 mA ~ 1500 mA
Coil Resistance 6.4 Ω (T=20° C)
Illustration 9 g03354830
P - Port pressure (kPa) vs Current (mA)
The proportional solenoid valve for variable relief is controlled directly by the machine ECM. When the ECM determines the requirements for relief pressure to the work tool, the ECM sends varying signals to the solenoids. Two of these solenoids are used to control relief pressure to the work tool for both one-way flow and two-way flow. The excess oil is sent to the return system for one-way flow.