070.550-IOM (JUN 2016)
Page 21
NGC GAS ROTARY SCREW COMPRESSOR
MAINTENANCE
TROUBLESHOOTING THE NGC COMPRESSOR
SYMPTOM
PROBABLE CAUSES and CORRECTIONS
SLIDE VALVE and/or SLIDE STOP
WILL NOT MOVE
• 4-way hydraulic control valve failed. Repair or replace.
• Slide stop indicator rod stuck. Contact Johnson Controls – Frick Service for assistance.
• Check both S.V. and S.S. feedback devices for wiring and resistance.
• Compressor must be running with sufficient oil pressure.
• Unloader piston stuck. Contact Johnson Controls – Frick Service for assistance.
• Piston Seals worn out/damaged. Contact Johnson Controls - Frick Service for assistance.
NOTICE
Unless the Service Technician has been certified by Johnson Controls – Frick to rebuild our compressors,
troubleshooting the compressor is limited to identifying the probable cause. If a mechanical problem is suspected
contact Johnson Controls – Frick Service. DO NOT ATTEMPT TO DISASSEMBLE COMPRESSOR.
TROUBLESHOOTING THE OIL PUMP AND SYSTEM
SYMPTOM
PROBABLE CAUSES and CORRECTIONS
PUMP WILL NOT PRODUCE
ENOUGH OIL PRESSURE AT
START UP
• Check that service valves are open.
•
Filter cartridges may be blocked. Check PSID across filters.
• Strainer may be blocked. Clean.
• Oil pressure regulator set too low or stuck open. Readjust or repair.
• Pump worn out. Repair or replace.
OIL PRESSURE RAPIDLY DROPS OFF
WHEN COMPRESSOR STARTS
• Main oil injection throttling valve too wide open or oil pressure regulating valve
improperly adjusted. Readjust both valves.
NOISE and VIBRATION
• Pump strainer blocked. Clean.
• Pump worn out. Repair or replace.
OIL PRESSURE DROPS AS HEAD
PRESSURE INCREASES
• Normal behavior. Set main oil injection & oil pressure for maximum head pressure
condition.
MAIN UNIT FILTER PSID IS TOO
HIGH
• Filters clogged with dirt. Replace.
• Oil is too cold. Allow oil to warm up and check again.
•
Service valve on filter outlet is partially closed. Open valves fully.
TROUBLESHOOTING THE HYDRAULIC SYSTEM
SYMPTOM
PROBABLE CAUSES and CORRECTIONS
SLIDE VALVE WILL NOT LOAD OR
UNLOAD
• Solenoid coils burned out. Replace.
• Valve closed. Open hydraulic service valves.
• Solenoid spool stuck or centering spring broken. Replace.
• Check LED on coil. If lit, there is power to the coil. Check coil.
• Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE VALVE WILL LOAD BUT
WILL NOT UNLOAD
• A side solenoid coil may be burned out. Replace.
• Dirt inside solenoid valve preventing valve from operating both ways. Clean.
• Check LED on coil. If lit, valve is functioning mechanically. Problem is electrical.
• Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE VALVE WILL UNLOAD BUT
WILL NOT LOAD
• A side solenoid coil may be burned out. Replace.
• Dirt inside solenoid valve preventing valve from operating both ways. Clean.
• Check LED on coil. If lit, valve is functioning mechanically. Problem is electrical.
• Solenoid may be actuated mechanically by inserting a piece of 3/16” rod against
armature pin and pushing spool to opposite end. Push A side to confirm unload
capability. If valve works, problem is electrical.
SLIDE STOP WILL NOT FUNCTION
EITHER DIRECTION
• Solenoid coils may be burned out. Replace.
• Solenoid service valves may be closed. Open.
• Manually actuate solenoid. If slide stop will not move mechanical problems are
indicated. Consult Johnson Controls - Frick Service.
