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Improper Flow Control & Check Valve Operation
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VARIATIONS IN FLOW
  Possible Causes   Remedy
1) Valve compensator spool binding. 1) See below :
 
a) Dirty spool.
b) Burrs on spool or body
 
a) Disassemble and clean. Drain, flush, and refill system with filtered recommended fluid.
b) Remove burrs on spool and body, or replace as necessary.
2) Insufficient pressure differential across the orifice due to low system pressure or increased system load. 2) Check system pressure and adjust to correct pressure setting or decrease the system load.
3) Fluid viscosity. 3) See below:
 
a) Too high.
b) Too low.
 
a) Preheat oil to normal operation temperature. Check fluid viscosity and change fluid to recommended viscosity.
b) Check fluid viscosity and change fluid to recommended viscosity. If using a needle valve and pressure compensated valve, change valve to a temperature-pressure compensated valve.
4) Leakage at or inside actuator. 4) Disassemble and repair actuator.
5) Erratic pilot pressure. 5) Check cause of pilot pressure fluctuations.
 
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IMPROPER FLOW RAsTE
  Possible Causes   Remedy
1) Needle valve adjustment incorrect. 1) Readjust needle valve to proper flow rate.
2) Line restriction. 2) See below:
 
a) Collapsed or kinked lines.
b) Improper tubing or hose size and/or fittings.
 
a) Replace collapsed or kinked lines.
b) Replace tube and hose with correct size and/or fittings.
3) Restrictions in valve passages or orifice area. 3) Disassemble and clean. Drain, flush, and refill system with filtered recommended fluid.
4) Compensator spool sticking. 4) See below:
 
a) Dirty.
b) Burrs on spool and/or body.
c) Broken spring.
 
a) Disassemble and clean. Drain, flush, and refill system with filtered recommended fluid.
b) Remove burrs on spool and body or replace spool or body.
c) Replace broken spring.
5) Fluid is too hot. 5) See below:
     
a) Reduce the amount of flow passing through relief valves.
b) Change to bypass type flow control, if possible.
c) Check the fluid viscosity. Drain and refill with correct viscosity fluid if applicable.
d) Install larger capacity flow.
6) Low pilot pressure. 6) See below:
 
a) Improper set pressure.
b) Collapsed or leaking pilot line.
 
a) Set the pilot pressure to the correct pressure.
b) Repair or replace collapsed or leaking pilot line.
 
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