SHIELD-FUEL LINE FITTING 2511255 - Caterpillar

HMU System
Illustration 1 g03718540
(1) Secondary steering pump
(2) Secondary steering pressure sensor
(3) Secondary steering diverter valve.
(4) Secondary steering relayThe secondary steering system provides temporary steering control when the primary steering system does not operate properly. The implement ECM and the power train control ECM monitor the steering and transmission control. The implement ECM monitors the following:
Steering pump pressure sensor
Secondary steering pump pressure sensor
Illustration 2 g03718623
Steering system with secondary steering active
(1) Secondary steering pump
(2) Secondary steering pressure sensor
(3) Secondary steering diverter valve.
(4) Secondary steering relay
(5) Check valve
(6) Check valve
(7) Primary steering pressure sensor
(8) Hand metering unit
(9) Steering control valve
(10) Pilot orifice
(11) Steering pump
(12) Hydraulic oil tankDuring normal machine operation, check valve (6) is off the seat, while check valve (5) is seated. Check valve (5) prevents pressure oil from flowing back to secondary steering pump (1).If steering pump (11) fails or the engine fails, the monitoring system will detect the failure from steering pressure sensor (7) . The implement ECM will send signal to the power train ECM of the failure and the power train ECM will activate secondary steering relay (4). The secondary steering relay then activates secondary steering pump (1). The secondary steering pump draws oil from hydraulic oil tank (12) and sends flow to secondary steering diverter valve (3). This causes check valve (5) to unseat and check valve (6) to seat. The high-pressure oil then flows through the rest of the steering system as it does with the primary steering pump pressure.
Illustration 3 g06063152
(13) Secondary steering indicator
(14) Action lamp indicatorAt the same time that the secondary steering system is being activated, a Warning Category 3 alerts the operator that engine shutdown should occur as soon as possible. Warning Category 3 will activate secondary steering indicator (13), cause master action lamp (14) to flash, the action alarm will sound, and an active fault message will appear on the graphical display.
The alarm system indicates that the primary steering system has failed.Use the secondary steering system to steer the machine to the nearest convenient location. When the machine comes to a complete stop, turn the start switch key to the OFF position.Continuing to operate the machine may result in damage to the system.
The secondary steering system is tested during engine start-up. During the three second test, secondary steering indicator (13) turns on, and the action alarm sounds. This test verifies that the secondary steering system is functional. The machine can be articulated during the three second start-up tests.