If the drive motor shaft is turning but the bar screen rake is not moving, which component is most likely damaged?

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

Answer: (C)

When the drive motor shaft turns but the bar screen rake doesn’t move, the problem is in the mechanism that transfers torque from the motor to the rake. The most likely damaged part is a component in the drive unit such as a shear pin or a disengaged clutch. A shear pin is meant to break if the drive is overloaded, so the motor can run but no torque gets to the rake. A disengaged clutch would do the same, stopping movement while the motor continues to run. Other options don’t fit this symptom: low influent level wouldn’t stop the drive train from moving the rake if the drive is intact, and issues with raw wastewater pumping units are unrelated to the rake drive. So the symptom points to a damaged drive pin or clutch that failed to transfer motion to the rake.