Positive displacement using pistons driven by a crankshaft. Single or two-stage.
Typical range
1–30 HP, up to 175 PSI (single-stage ~125 PSI)
Best for
Intermittent duty, small shops, portable use.
Components
- Crankcase & crankshaft
- Pistons, rings, cylinders
- Intake & discharge valves (reed/plate)
- Intercooler (two-stage)
- Aftercooler
- Pressure switch
- Unloader valve
- Check valve
- Receiver tank
Common issues
- Worn rings → oil carryover, low pressure
- Stuck/broken valves → loss of capacity, overheating
- Unloader failure → motor stalls on restart
- Loose belt → slow pump-up, squeal
Maintenance
- Daily: drain tank, check oil level, check for leaks
- Monthly: clean intake filter, check belt tension
- 500 hrs / annual: change oil, inspect valves, torque head bolts