If the drive motor shaft is turning but the bar screen rake is not moving, what is the most likely cause?

• A. Raw wastewater pumping units out of service
• B. Sheared pin or disengaged clutch on drive unit
• C. Low influent level
• D. None of the above

Answer: (B)

When the drive motor shaft is turning but the bar screen rake isn’t moving, the problem is in the drive transmission between the motor and the rake. A sheared pin or a disengaged clutch on the drive unit would disconnect the motor’s torque from the rake, so the motor can spin without transferring motion to the rake. That’s why this is the most likely cause—the motor is alive, but the mechanism that transmits its movement to the rake has failed.

The other possibilities don’t fit the symptom as well: issues like raw wastewater pumping units being out of service or a low influent level affect flow or loading, not the mechanical linkage that actually moves the rake. So the correct focus is inspecting the drive coupling, pin, or clutch for damage or disengagement and restoring that connection to get the rake moving again.