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Formsprag Model HSB Backstopping Clutches for Wastewater Plant

A global pump OEM contacted various backstopping clutch suppliers as they were experiencing problems with pumps at a wastewater facility in Madagascar. The pumps, on a common manifold, were rotating backward when their respective drive motors were not powered up.

Ultimately, HSB backstopping clutches from Formsprag were selected over competitive models based on rapid responsiveness, superior product quality and a long supply history. The OEM also continued to specify Formsprag HSB backstops on future projects.

To meet the application requirements, Formsprag supplied Model HSB-900 clutches, with a torque capacity of 18,000 lb.ft. (24,480 Nm). HSB Series clutches are intended for use as backstops on the high speed shaft or intermediate shaft of a reducer.

HSB units are comprised of standard FSO clutch with the addition of an aluminum cast oil reservoir with cooling fins. HSB models have a spacer replacing the seal at the reservoir end to permit free oil flow between the clutch and reservoir. The reservoir features a flush oil sight gauge and a combination breather and oil filter.

The FSO-900 clutch incorporated into the HSB-900 features PCE® sprags with Formchrome® and Formsprag “Free-action” retainers. Exclusive Formchrome sprags provide extra-long life, maximum wear resistance and lower maintenance costs. Ultra-hard Formchrome sprags are made by diffusing chromium into the surface of hardened high-carbon alloy steel to form a chromium-carbide alloy.

Model HSB Backstopping Clutches


  • Comprised of an FSO clutch combined with an oil reservoir
  • Torque capacity of 18,000 lb.ft. (24,480 Nm)
  • Formsprag exclusive PCE┬«sprag design
  • Reservoir features a flush oil sight gauge

Contact Information

Formsprag Clutch
23601 Hoover Rd.
Warren, MI 48089 - USA
Toll Free: 1-800-348-0881 (Press #1)
Phone: 586-758-5000
Fax: 586-758-5204

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