Komatsu 730E, Shop Manual

A3-26

General Safety & Operation

A03048

EMERGENCY STEERING SYSTEM

Operation

This truck is equipped with an emergency steering
system. This system is a backup in the event of loss
of oil supply to the main steering system. The
emergency steering system was designed to meet or
exceed SAE J1511 and ISO 5010 standards.

If the low steering system pressure indicator light and
alarm are activated, a failure in the hydraulic oil
supply to the steering and brake system exists. When
the alarm is activated, typically there is enough
hydraulic pressure stored in the brake and steering
accumulators to allow brief operation of the steering
and brake functions. However, this oil supply is
limited. Therefore, it is important to stop the truck as
quickly and safely as possible after the alarm is first
activated.

If the oil supply pressure drops to a predetermined
level, the low brake pressure warning light will also
illuminate. If the oil pressure continues to decrease,
the brake auto-apply feature will activate the service
brakes to stop the truck.

Pre-Operation Testing

NOTE: Komatsu recommends that operators perform
this test to verify that the steering accumulator
precharge pressure is adequate at the beginning of
each shift before operating the truck.

Ensure no one is near the front tires during this
test. All personnel are warned that the clearances
change when the truck is steered and this could
cause serious injury. 

This test can only be performed with an empty truck. 

1. Park the empty truck on flat, level ground.

Lower the dump body onto the frame and stop
the engine. Ensure the key switch is in the OFF
position.

2. Wait at least 90 seconds to verify that all

hydraulic pressure has been relieved from the
steering accumulators. Turn the steering wheel
from stop to stop. If the front wheels do not
move, there is no hydraulic pressure.

3. Check the hydraulic tank oil level. The oil level

must be visible in the center of the upper sight
glass and must not cover the entire upper sight
glass. Add oil if necessary. 

DO NOT overfill.

4. Turn the key switch to the ON position, but DO

NOT start the engine.

a.

Steering system pressure:

 Verify that the low

steering pressure warning light is
illuminated. If it is not illuminated,
immediately notify maintenance personnel.
DO NOT operate the truck until the problem
is corrected.

b.

Steering accumulator precharge: 

Verify that

the low accumulator precharge warning light
is not illuminated and the warning buzzer is
not sounding. If the warning light is
illuminated and the buzzer is sounding,
immediately notify maintenance personnel.
DO NOT operate the truck until the problem
is corrected.

5. 

Start the engine and allow the steering

accumulators to fully charge. Turn the steering
wheel so that the front wheels are straight.

6. Check the hydraulic tank oil level while the

engine is on.

a. If the oil level is visible in center of the lower

sight glass and does not cover the entire
lower sight glass, the steering accumulators
are adequately charged. Proceed to Step 7.

b. If the oil level is below the lower sight glass,

the steering accumulators are not
adequately charged. Stop the engine and
turn the key switch to the OFF position.
Immediately notify maintenance personnel.
DO NOT operate the truck until the problem
is corrected.

7. Shut the engine off by using the engine stop

button located on the center console. Leave the
key switch in the ON position. This allows the
steering accumulators to retain their hydraulic
charge. 



If the warning light and buzzer do activate,

turn the key switch OFF and notify

maintenance personnel. DO NOT operate

the truck until the problem is corrected.



If the steering accumulators are adequately

charged, the low steering pressure warning

light and the low accumulator precharge

warning light will not illuminate. Continue to

the next step.