26.5 INSUPECTION PROCEDURES WHEN CYLINDER SINKE
Ins
ection of telesco
in
cylinder
(1) Pre
aration before ins
ection
①Allow booms to be horizontal and extend them fully to put a
mark on each boom section (refer to Fig. 1).
②Raise booms to their maximum to sling a load.
③In order to release pressure remained in the telescoping system,
stop the engine and shift the manual lever for telescoping
booms.
(2) Startin
ins
ection
④Remove the retraction hose to check if oil overflows
continuously out of the cylinder port of retraction side.
At he same time, also check that which boom section sinks
how far to grasp condition of booms as a whole.
If no oil flows out of the port of retraction side, the cylinder is
normal.
⑤Next, remove the extension hose, and if oil overflows
continuously out of counter-balance valve port of extension
side, there may be faulty on the seat surface of counter-balance
valve (refer to Fig. 3). Fig1
In addition, check how far boom3 sinks simultaneously.
Caution:
In order to release pilot pressure in the retraction side,
be sure to remove the extension hose after the
retraction hose has been removed (refer to Fig. 2).
Since overflowing oil out of the port on retraction side
means internal leakage in the cylinder, check tele1 and
tele2 separately.
Be sure to measure the how far each boom sinks as it is
an important point for judging that it is normal or
abnormal. Fig2
(3) Ins
ection of tele1
⑥Extend booms to a position where it is a little bit shorter than
2-section boom to put a mark on the boom (refer to Fig. 4).
⑦Raise booms to their maximum to sling a load.
⑧In order to release pressure remained in the telescoping system,
stop the engine and shift the manual lever for telescoping
booms.
⑨Remove the retraction hose.
If oil overflows out of cylinder port of retraction side and
boom2 sinks, there may be internal oil leakage in tele1.
In addition, check how far boom2 sinks simultaneously.
(4) Ins
ection of tele2
⑩Allow booms to be horizontal and extend them fully to put a
mark on each boom section (refer to Fig. 1).
⑪Raise booms to their maximum to sling a load.
⑫In order to release pressure remained in the telescoping system,
stop the engine and shift the manual lever for telescoping
booms.
⑬Remove the retraction hose.
If oil overflows out of cylinder port of retraction side and
boom3 sinks, there may be internal oil leakage in tele2.
In addition, check how far boom3 sinks simultaneously.
The same procedures in checking boom sinkage are applied for
5-section boom
Be sure to check the boom sections one by one reliably. Fig3
Put a mark
on each boom
Load
Put make on bo
Load
Counterbalancevalve
Fault in seat surface
( 26 - 6 )
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