Pump · PCP
Rotor
A single-helix steel rod, usually chrome plated, that turns inside the stator.
What it does
Its rotation moves the sealed cavities upward. The fit between rotor and elastomer sets how well it pumps.
Basics
| Material | Alloy steel, hard chrome plated |
| Geometry | Single external helix |
| Fit | Sized against the stator (interference) |
Common failures
- Chrome wear exposing base metal
- Wrong space-out (rotor partly out of the stator or tagging)
- Rotor breaks at the rod connection
Troubleshooting
- Symptom
- Low output with normal torque
- Likely cause
- Rotor partly out of the stator
- What to check
- Re-tag and re-space the rotor
- Symptom
- Cyclic high torque, knocking
- Likely cause
- Rotor tagging the tag bar
- What to check
- Raise the rotor per the space-out sheet