Philadelphia Gear

Fan Drives

Fan drives are often used inside coal-fired power plants to draw combustion gases from the boiler through an air filtration system in order to remove fly ash from the boiler exhaust gases. Fan speed must be varied in this type of induced draft application so that airflow can be varied to accommodate the different boiler operating levels.

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Due to the operating characteristics of induced draft fan drive systems, our fan drives all include our patented Synchrotorque® technology:

  • With a constant input speed, the output (fan) speed can be varied from the input speed (clutch fully engaged), down to approximately 25% of the input speed (clutch slipping)
  • Once the clutch is fully engaged (locked-up), the Synchrotorque hydroviscous drive transmits 100% of torque and speed, making it the most efficient variable speed drive on the market today
  • The hydroviscous drive can be used with gearing elements to combine the variable speed feature with step-up or step-down gearing
  • These units can transmit torque in either direction of rotation, while providing controlled acceleration and deceleration
  • If, for any reason, the load exceeds design limits, the clutch will “slip” and protect the drive train from being unnecessarily damaged
  • These units allow for the option of a “no load” start-up of the prime mover