Views: 8679 Author: Site Editor Publish Time: 2025-05-05 Origin: Site
Oil carryover in screw compressor discharge is one of the most common operational failures. It degrades compressed air quality, damages downstream equipment, and may cause production interruptions.
This article systematically analyzes six root causes, provides step-by-step troubleshooting procedures, and offers targeted solutions.
1.1 Oil Separator Element Damage
Aspect | Description |
|---|---|
Symptoms | Perforation, rupture of the element |
Consequence | Oil-air mixture bypasses separation, large amounts of oil exit with air |
1.2 Return Line Failure
Aspect | Description |
|---|---|
Symptoms | Blockage, rupture, incorrect installation |
Consequence | Oil accumulated at separator bottom cannot return to compressor |
1.3 Low System Pressure
Aspect | Description |
|---|---|
Symptoms | Operating pressure below design value |
Consequence | Centrifugal force insufficient, oil content entering separator exceeds capacity |
1.4 Minimum Pressure Valve Failure
Aspect | Description |
|---|---|
Symptoms | Valve cannot maintain minimum system pressure |
Consequence | Return line cannot function, oil cannot return to compressor |
1.5 Excessive Oil Filling
Aspect | Description |
|---|---|
Symptoms | Oil level above sight glass midpoint |
Consequence | Even with proper separation, gas carries excess oil |
1.6 Poor Oil Quality
Aspect | Description |
|---|---|
Symptoms | Unqualified oil or expired service life |
Consequence | Cooling and separation ineffective, oil carryover inevitable |
Step 1: Initial Confirmation
Start compressor and reach rated pressure
Slowly open discharge gate valve (minimum opening)
Use dry paper towel to test discharge airflow
Result: Immediate discoloration and oil droplets confirm oil carryover.
Step 2: Fault Localization
Observation | Likely Cause | Next Action |
|---|---|---|
Continuous heavy mist + increased return flow | Separator damage or excess oil | Check oil level and separator |
Continuous heavy mist + no return flow | Return line blockage or rupture | Inspect return line |
Initial mist clears, then fails when valve fully opened + pressure below setpoint | Minimum pressure valve failure | Replace valve |
Oil-heavy discharge from automatic blowdown on shutdown | Automatic blowdown valve damaged | Replace valve |
3.1 Oil Separator Element Damage
Prevention: Pre-operation inspection, follow procedures, regular maintenance
Solution: Replace immediately upon detection of damage
3.2 Return Line Failure
Check: Verify separator pressure drop first
Solution: Clear blockages, reweld cracks, or correct installation
Critical Installation Requirements:
Maintain unobstructed flow (welding must not reduce inner diameter)
Maintain 3–4mm clearance between return line tip and separator sump
3.3 Low System Pressure
Solution: Reduce system load to achieve rated operating pressure
3.4 Minimum Pressure Valve Failure
Solution: Replace valve (cannot be repaired)
3.5 Excessive Oil Filling
Standard: Maintain oil level below sight glass midpoint
Solution: Drain excess oil
Check requirements: Level compressor; check before startup or 30 minutes after shutdown
3.6 Poor Oil Quality
Principle: Follow manufacturer specifications
Management: Track fill dates; change at specified intervals
Quality control: Never use unqualified oil
No. | Precaution | Reason |
|---|---|---|
1 | Inspect new element for damage/deformation | Prevent repeat failure |
2 | Clean mating surfaces of body and cover | Ensure proper sealing |
3 | Check for conductive material on sealing gasket | Prevent static discharge (oil rotates at high speed) |
Screw compressors are reliable, but 30% relies on operation, 70% on maintenance.
Phase | Focus |
|---|---|
Pre-start | Check oil level, oil quality, separator condition |
Running | Monitor system pressure, discharge temperature, return line sight glass |
Post-shutdown | Record data, plan maintenance |
Eliminating failures in their early stages ensures long-term reliability and reduces operating costs.
Oil Carryover Detected
↓
Paper Test (Confirm超标)
↓
Observe Return Line Sight Glass
├── Increased return flow → Separator damage OR excess oil
└── No return flow → Return line blockage/rupture
↓
Open discharge valve fully; check system pressure
├── Below setpoint → Minimum pressure valve failure
└── Normal → Check oil quality
↓
Execute targeted repair
