349E, 349F and 352F Excavators and 349E MHPU Mobile Hydraulic Power Unit Tool Control System Caterpillar

Flow Limit Valves

Illustration 1	g03621658
Flow limit valves located in pump compartment (typical example)

Illustration 2	g03621878
Flow limit valves located on the main control valve (typical example)

Illustration 3	g02304193
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.

Illustration 4	g02263554
A - Port pressure (kPa) vs Current (mA)

The machine ECM controls flow limitation pressure which is decided by throttle dial position, engine speed, and pump pressure through this solenoid.

The tool control system calculates the negative flow control pressure equivalent to the flow when the work tool is used at the set work tool parameters. The proportional reducing valve then sends out pressured oil for flow control of drive pump and idler pump.

Attachment Valves

Illustration 5	g03620996
Attachment valves (A1 and A2) located in pump compartment (typical example)

Illustration 6	g03623120
Attachment valves (A3) located in swing motor compartment (typical example)

Illustration 7	g03623202
Attachment valves (A3) located in pump compartment (typical example)

Illustration 8	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.

Illustration 9	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.

Boom DOWN / Stick IN Pressure Limit Valves

Illustration 10	g03623318
Boom DOWN / Stick IN pressure limiting valves located beneath main control valve (typical example)

Illustration 11	g02304374
Valve cutaway, 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.

Illustration 12	g02304414
A - Port pressure (kPa) vs Current (mA)

The Boom DOWN and Stick IN pressure limiting valves are used on the Combined Function - Electric Control system.

These proportional reducing valves electronically control spool shift pressure of the boom DOWN and stick IN control valves. This operation will allow better operability of the work tool by decreasing the boom DOWN and stick IN speed that is caused by a heavy work tool.

Variable Relief Valves

Illustration 13	g03618777
Variable relief valves located above the swing motor compartment (typical example)

Illustration 14	g02304476
Solenoid valve, hydraulic schematic symbol, and electrical connector designation

Note: The values in Table 4 are for bench testing only. Values may not represent parameters for machine systems specifications.

Illustration 15	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 variable relief valves are used to control the oil flow sending oil to the return system for one-way flow.