An interesting option for Tri-Rotor pumps is the ability to offer both the Solid Head and Bypass Head versions with a permanently reduced stroke.  This is great for those applications targeting a desired flow rate less than full flow at a set motor speed.  This is not available (or needed) for the third head type, the Variable Volume Control Head, as that head already has a built-in, automatic stroke adjustment feature.

The reduced stroke pumps, also known as de-stroked pumps or pumps having offset heads, are typically measured as a fraction of full flow and are manufactured by re-locating the shuttle pin at the appropriate place on the head to achieve the desired fractional pump stroke.  An infinite number of shuttle pin locations are available but the standard fractional stroke head options offered by Tri-Rotor are ¼ stroke, ½ stroke, and ¾ stroke.

Calculating the flow of a reduced stroke pump is very easy as it is directly proportional to the value of the full flow version.  For example, a Series 20 pump that achieves 30 GPM at 1800 RPM would achieve 22.5 GPM at a ¾ stroke, 15 GPM at a ½ stroke, and 7.5 GPM at a ¼ stroke.

Features and Benefits of Tri-Rotor’s Reduced Stroke Pump

  • Provides capability to target a flow rate at an ideal motor speed
  • Allows higher motor speed (RPM) for viscous fluids for better performance
  • Allows pump to pass larger solids than standard pump (see table below)
  • Helps to keep motor from being overloaded
  • Increases the already long life of a Tri-Rotor pump

Reduced Stroke Availability by Tri-Rotor Model

Tri-Rotor Model ¼ Stroke ½ Stroke ¾ Stroke
20D Yes Yes Yes
20DX Yes Yes Yes
20CP Yes Yes Yes
20CPX Yes Yes Yes
40A No Yes No
40AX No Yes No
80B Yes Yes Yes
80BX No No Yes
100C Yes Yes Yes
100CX No No Yes
120A Yes Yes Yes
120AX No No Yes
200A Yes Yes Yes
200AX Consult Factory Consult Factory Consult Factory
200T Yes Yes Yes
200TX Consult Factory Consult Factory Consult Factory

Maximum Solids Passage for Tri-Rotor Pumps

Tri-Rotor Series ¼ Stroke ½ Stroke ¾ Stroke Full Stroke
20, 20CP .233" .163" .093" .023"
40 .329" .227" .124" .022"
80, 100, 120 .481" .333" .185" .037"
200, 220 .632" .444" .257" .069"

If you have any questions about Tri-Rotor’s reduced stroke pumps, feel free to contact us.