349F and 352F Excavators Machine System Caterpillar


Control Valve (Boom Lowering)

Usage:

352F-VG A9J
The boom lowering control valves are located on the head end of the boom cylinders.

The boom lowering control valve has two functions:

  • The boom lowering control valve prevents the boom from falling if a hydraulic supply line fails or if a supply tube to a boom cylinder fails.

  • The boom lowering control valve allows the operator to manually lower the boom when the engine is shut down.

Reference: For information on lowering the boom manually, see Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped".



Illustration 1g03408734
Partial schematic
(1) Boom cylinders
(2) Boom lowering control valves
(3) Main control valve
(4) Manual boom lower
(5) Pilot control valve

BOOM RAISE Operation



Illustration 2g03409537
Boom lowering control valve
(1) Spool
(2) Orifice
(3) Passage
(4) Port
(5) Port (pilot)
(6) Port (boom cylinder head end)
(7) Passage
(8) Check valve
(9) Spring
(10) Port
(11) Line relief valve
(12) Tank port
(13) Drain port

When the operator moves the joystick to the BOOM RAISE position, oil from the main control valve flows through port (4) in the boom lowering control valve. As the oil pressure increases, check valve (8) shifts against the force of spring (9). This action allows oil to flow through port (10), passage (7), and port (6) to the head end of the boom cylinders. The rod is extended and the boom raises.

BOOM LOWER Operation



Illustration 3g03408749
Boom lowering control valve
(1) Spool
(2) Orifice
(3) Passage
(4) Port
(5) Port (pilot)
(6) Port (boom cylinder head end)
(7) Passage
(8) Check valve
(9) Spring
(10) Port
(11) Line relief valve
(12) Tank port
(13) Drain port

When the operator moves the joystick to the BOOM LOWER position, pilot oil flows from the pilot control valve to port (5) of the boom lowering control valve. The pilot pressure moves spool (1) to the left. Orifice (2) opens allowing oil to flow to passage (3).

As the joystick is moved further to the BOOM LOWER position, the pilot pressure in port (5) increases. Spool (1) shifts further to the left which allows more oil from passage (7) to flow to passage (3). Oil from the head end of the boom cylinder now flows through port (6), to port (4), and then to the main control valve. The boom cylinder rod retracts and the boom lowers.

Manual Boom Lower



Illustration 4g02076115
Emergency valve group
(14) Port
(15) Seat
(16) Locknut
(17) Valve
(18) Ball
(19) Port

As seat (15) is turned counterclockwise, ball (18) will shift. As ball (18) is shifted, oil is allowed to flow through port (14) and valve (17) to port (19). Oil from the head end of the boom cylinder flows through port (19) to the hydraulic tank. This action allows the boom to lower.

Reference: For information on the location of the manual lower valve, see Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped".

Caterpillar Information System:

349F and 352F Excavators Hydraulic System Relief Valve (Main) - Heavy Lift
349F and 352F Excavators Hydraulic System Solenoid Valve (Proportional Reducing) - Power Shift System
2013/07/25 New Software Flash File Extension Requires Caterpillar Electronic Technician (Cat ET) 2013B {0785, 7620}
2013/07/25 A New Coupling Assembly Is Used on Heat Exchangers for Certain 3500B and 3500C Engines {1379}
C32 Auxiliary Engine Engine Electronics
3512C Petroleum Engines Fuel Control Actuator - Remove and Install - Dynamic Gas Blending
C7.1 Engines NOx Conversion Is Low
3512C Petroleum Engines Gas Pressure Regulator - Remove and Install
2013/11/21 A New Jacket Water Outlet Elbow Is Used on Certain C175 Marine and Petroleum Engines {1380}
C7.1 Industrial Engine Diesel Exhaust Fluid Module - Assemble
C7.1 Industrial Engine Diesel Exhaust Fluid Module - Disassemble
C15 and C18 Engines for Caterpillar Built Machines Fuel Filter and Water Separator
2013/07/30 Delphi Fuel Injection Pumps on 3054, 3056, 3054B, 3054C, C3.3, C4.4 (MECH), and C7.1 (MECH)Engines {1251}
349F and 352F Excavators Machine System Control Valve (Stick Lowering)
2013/07/22 New Bolts and Washers Are Used in Certain 3500 Engines With Oil Scavenge Pumps {1312, 7553}
3512E Petroleum Engines Turbocharger - Remove and Install
C32 Marine Engine Maintenance Interval Schedule
349F and 352F Excavators Hydraulic System Swing Motor
349F and 352F Excavators Machine System Relief Valve (Swing)
349F and 352F Excavators Hydraulic System Oil Makeup (Swing System)
226-2380 Adjustable C-Hook Extension{0374, 0599, 0632, 0727, 1122, 3258, 4050, 4084, 4208, 7561} 226-2380 Adjustable C-Hook Extension{0374, 0599, 0632, 0727, 1122, 3258, 4050, 4084, 4208, 7561}
349F and 352F Excavators Machine System Solenoid Valve (Fine Swing) - If Equipped
2013/08/05 New Alternator Guards are Used on Certain 3500 Engines {7174}
349F and 352F Excavators Machine System Travel Motor
Back to top
The names Caterpillar, John Deere, JD, JCB, Hyundai or any other original equipment manufacturers are registered trademarks of the respective original equipment manufacturers. All names, descriptions, numbers and symbols are used for reference purposes only.
CH-Part.com is in no way associated with any of the manufacturers we have listed. All manufacturer's names and descriptions are for reference only.