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TM 5-2420-224-34
BACKHOE CONTROL VALVE, DIPPER AND BUCKET SECTION VALVES
R E P A I R (CONT)
Leak Test
NOTE
Perform steps 1 thru 3 to check high-pressure safety relief valves.
Stroke pump until pressure is built up to less than opening pressure of safety relief valve.
1.
NOTE
It normally takes minimum of 15-30 seconds to bleed down to approximately 1000 psi
(68 bar).
2.
Allow pump to sit and monitor pressure for 30-45 seconds. Pressure should have dropped to
approxirnately 500 psi (34 bar) and should not drop off to 0 for a few minutes.
If pressure drops off quicker, there is excessive leakage in circuit being tested. Check following:
3.
Tube connections
Safety relief packings
Poppet seat in safety relief valve
Oil passing by valve spool
Valve spool not returning to neutral position
Possible cracks in backhoe control valve
NOTE
Perform steps 4 thru 6 to check low-pressure safety relief valves.
4.
Stroke pump until pressure is built up to less than opening pressure of safety relief valve.
NOTE
It normally takes minimum of 15 seconds to bleed down to approximately 300 psi (20.4
bar).
Allow pump to sit and monitor pressure for 30-45 seconds. Pressure should not have dropped to, and
5.
should not drop off to, 0 for a few minutes.
If pressure drops off quicker, there is excessive leakage in circuit being tested. Check following:
6.
Tube connections
Safety relief packings
Poppet seat in safety relief valve
Oil passing by valve spool
Valve spool not returning to neutral position
Possible cracks in backhoe control valve
NOTE
Follow-on Maintenance:
Install dipper section valve or bucket section valve in backhoe control valve (page
20-79

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