Doosan 7/26E, Operation And Maintenance Manual

Page: 61 / 90

OPTIONS 57
7/26E, 7/31E, 7/41
DESCRIPTION
Chalwyn valves provide emergency overspeed shutdown protection
for diesel engines and are the most effective way of preventing a
runaway situation. The valves completely block the engine air intake
system, cutting off an uncontrolled external fuel source and the air
required to keep the engine running.
OPERATING INSTRUCTIONS
Adjustment
Once the Chalwyn valve is installed, adjustment of the overspeed trip
setting is carried out using the adjuster and locknut. Basically rotating
the adjuster clockwise will increase the engine speed at which
automatic shutdown occurs.
1. Start engine. Slowly accelerate. Note speed at which shutdown
occurs.
2. Remove hose at air inlet to Chalwyn valve to expose the adjuster
and locknut.
3. Release locknut. Turn adjuster clockwise one turn. Tighten locknut.
4. Refit inlet hose to Chalwyn valve.
5. Start engine. Slowly accelerate. Note speed at which shutdown
occurs.
6. Repeat the above steps ”2” to ”5” until the first setting at which the
engine does not shut down at high idle speed.
Then either:
A. Use the results of shutdown speed versus adjuster setting as a
calibration check to make a final adjustment to give the required
setting (typically 10% to 15% over high idle),
or:
B. If a very precise setting is not required, turn the adjuster a further
one turn clockwise to take the shutdown above high idle speed by
a suitable margin. When using this setting procedure it may be
found that the engine occasionally shuts down during the normal
operation. If so, turn the adjuster clockwise by a further one half
turn.
7. Ensure the adjuster locknut is fully tightened.
MAINTENANCE
Three Monthly:
1. Disconnect the intake pipework and release the valve from any
support brackets etc., to allow it to be removed.
2. Inspect the valve internally for cleanliness. If necessary, clean in
paraffin or white spirit, taking normal precautions. Dry the valve
thoroughly.
3. Check that there is no excessive wear and that the valve moves
smoothly over its complete operating stroke. DO NOT LUBRICATE.
4. Refit the valve. Check valve setting.
OPTION - OVERSPEED (CHALWYN) VALVE
A. Adjuster
B. Locknut
C. Hold with spanner when adjusting
D. Air flow
NOTE: The recommended routine maintenance period is three
months. This period is dependent on the operating conditions of the
engine and, by experience, may need to be varied.
NOTE: Turbocharged engines - when setting up a valve on a
turbocharged engine using the preceding method, it may be found
that at high power outputs, the engine will shut down at lower speed
than required. If this occurs, further small adjustments in steps of one
half turn clockwise should be made until the problem is eliminated.
Jammed valve - if in the course of adjusting the valve it jams on its
seat, release by turning CLOCKWISE viewed from adjuster end of
valve.
Insufficient Adjustment - should there be insufficient adjustment
available to set the required overspeed trip-point, the outlet locknut
should be released and the outlet adjuster rotated anticlockwise by
four turns. The outlet locknut should then be treated with a thread
lock adhesive and security tightened. Further adjustment to the inlet
adjuster as per above instructions is then continued.