Maintenance

Proper maintenance is essential for reliability, efficiency, and lifespan of piston compressors.

Maintenance Program

Daily Checks

Task	What to Verify
Oil level	Between min/max marks on sight glass
Drain condensate	Tank and traps
Operating pressure	Within normal parameters
Abnormal noises	Knocking, squealing, hissing
Vibrations	Excessive or unusual
Visible leaks	Oil, air, water
Temperature	Discharge not excessive

Weekly Maintenance

Task	Procedure
Intake filter	Inspect, clean if necessary
Belt tension	Verify correct deflection
Safety valves	Manual operation test
Connections	Verify tightness
Exterior cleaning	Remove dust and dirt

Monthly Maintenance

Task	Procedure
Intake filter	Replace based on condition
Oil	Verify color and level
Valves	Inspect for leaks
Coolers	Clean fins
Electric motor	Verify amperage

Quarterly/Semi-Annual Maintenance

Task	Procedure
Oil change	Drain and replace
Oil filter	Replace
Intake/discharge valves	Detailed inspection
Belts	Replace if worn
Alignment	Verify motor-compressor

Annual/Overhaul

Task	Procedure
Piston rings	Measure wear, replace
Cylinders	Measure wear, bore if necessary
Valves	Recondition or replace
Bearings	Inspect, replace if necessary
All gaskets	Replace

Compressor Oil

Oil Verification

    Oil sight glass
    ┌─────────────┐
    │     MAX ────│─── Maximum level
    │             │
    │  ███████    │←── Correct level
    │             │
    │     MIN ────│─── Minimum level
    └─────────────┘

Oil Color	Meaning
Amber/golden	Normal, new oil
Dark brown	Normal, change due soon
Black	Contaminated, change immediately
Milky/white	Water mixed in, serious problem

Oil Change

Procedure:

1. Run compressor 10 min to warm oil
2. Shut down and depressurize completely
3. Place container under drain plug
4. Remove plug and drain hot oil
5. Reinstall plug with new gasket
6. Add new oil to correct level
7. Run 5 min and recheck level

Hot Oil

Hot oil drains better but can cause burns. Use gloves and proper protection.

Valves

Valves are critical components and a common source of problems.

Symptoms of Defective Valves

Symptom	Possible Cause
Capacity loss	Valve not sealing well
Overheating	Valve stuck open
Knocking	Loose or broken valve
Difficult starting	Discharge valve leaking
Continuous operation	Valves not holding pressure

Valve Inspection

    Typical reed valve:

    ┌───────────────────┐
    │   Spring          │
    │      │            │
    │   ┌──▼──┐         │
    │   │ Reed │ ← Check:
    │   └──┬──┘     - Cracks
    │      │        - Deformation
    │  ════╧════    - Wear
    │   Seat     ← Check:
    │              - Scratches
    └──────────────- Pitting

Reconditioning

1. Disassemble complete valve
2. Clean all parts
3. Inspect reeds/discs
4. Verify seats (lap if necessary)
5. Replace springs
6. Assemble and test

Piston Rings

Ring Wear

Indicator	Meaning
Capacity loss	Rings not sealing
Oil consumption	Worn rings
Oil in air	Rings not retaining oil
Cylinder knock	Excessive clearance

Wear Measurement

    Gap method:

    ┌─────────────────────┐
    │      Cylinder       │
    │  ┌───────────────┐  │
    │  │   ═══════     │  │ ← Insert ring
    │  │      ↕        │  │
    │  │    Gap        │  │ ← Measure with feeler gauge
    │  └───────────────┘  │
    └─────────────────────┘

Ring Gap	Condition
Specification	New/good
1.5x specification	Monitor
2x specification	Replace

Belts and Pulleys

Belt Tension

    Motor         Compressor
      ○───────────────○
          ╲       ╱
           ╲     ╱
            ╲   ╱
             ╲ ╱
              ▼
         Correct deflection:
         ~1/2" per foot of span

Belt Inspection

Condition	Action
Side cracks	Replace
Fraying	Replace
Glazed/shiny	Replace
Loose tension	Adjust
Misalignment	Correct

Replace as a Set

Always replace all belts in a set at the same time, even if only one is damaged.

Coolers

Intercooler/Aftercooler Cleaning

Coolers become clogged with dust and reduce efficiency:

Procedure:

1. Shut down and depressurize
2. Blow with compressed air (opposite to normal flow direction)
3. For stuck dirt, use degreaser cleaner
4. Rinse if liquid cleaner was used
5. Verify no obstructions remain

Cleaning Frequency

Environment	Frequency
Clean (office)	Quarterly
Normal industrial	Monthly
Dusty	Weekly
Heavily contaminated	Daily

Troubleshooting

Quick Diagnosis

Problem	Probable Causes	Solution
Won't start	Thermal, electrical, high pressure	Check protections, depressurize
Frequent cycling	Leak, high demand, pressure switch	Find leaks, verify setting
Low pressure	Valves, rings, leaks	Inspect components
Overheating	Dirty cooler, low oil, valves	Clean, check level
Oil in air	Rings, separator	Inspect wear
Excessive noise	Valves, bearings, belts	Locate and inspect
Vibration	Imbalance, looseness, wear	Check mounting and components

Maintenance Log

Keep a record of all activities:

┌──────────────────────────────────────────────────┐
│ MAINTENANCE LOG                                  │
├──────────┬──────────┬────────────┬───────────────┤
│ Date     │ Hours    │ Activity   │ Observations  │
├──────────┼──────────┼────────────┼───────────────┤
│ 01/15/24 │ 1,250    │ Oil        │ Dark oil      │
│          │          │ change     │               │
├──────────┼──────────┼────────────┼───────────────┤
│ 02/01/24 │ 1,400    │ Intake     │ Very dirty    │
│          │          │ filter     │               │
└──────────┴──────────┴────────────┴───────────────┘

Valuable History

A good maintenance log helps:

• Predict when repairs will be needed
• Identify recurring problems
• Plan maintenance budget
• Demonstrate warranty compliance