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Tri-Rotor’s Variable Volume Control Head (“V-Head”) pumps are equipped with a spring set at a certain spring tension which maintains the stroke of the pump.  Running at a constant speed, the pump automatically responds to change in line pressure.  When pressure rises above the preset response point, the pump automatically shortens its stroke and proportionally discharges a lower flow rate.  If the pressure rises above the set spring force, the pump will automatically shorten its stroke to zero while the motor is still running, resulting in zero flow.  The pump will automatically increase delivery when the pressure drops.

In addition to the automatic variable volume control head, Tri-Rotor offers models with a Manual Flow Control (MFC), which allows a manual adjustment of the pump stroke to control pump flow rate.  A precise metering version of this, the Vernier Flow Control (VFC), is also available.  All of these models also are available with an option, called the Pressure Regulating Control (PRC), to manually adjust the allowable pump discharge pressure.

Jacketed pump options are available for Tri-Rotor variable volume control head pumps.

Features and Benefits of Tri-Rotor Variable Volume Control Head Pumps

  • Automatic control of variable displacement
  • Elimination of the need for bypass or pressure relief valve
  • Minimum heat generation
  • Lower power requirements
  • Maintenance of exact operating pressure
  • Elimination of excessive pressures
  • Practically noiseless operation
  • All models available with standard or heavy duty springs
  • CW and CCW rotations available
  • May be run in reverse temporarily to strip lines
  • Operating pressures up to 100 PSI

How Variable Volume Control Works

The variable volume control changes the length of stroke of the piston and shuttle to vary the volume of material displaced by the pump.  The length of stroke is determined by the position of an off-center shuttle pin.  This position is controlled by a plunger in a cylinder of the variable volume control head.  The cylinder connects with the pump output and intake ports.  If pump output is blocked or restricted, pressure builds up and forces the plunger downward against spring pressure.  This moves the off-center shuttle pin more nearly on center and reduces the pump flow.  If the pressure is high enough, the shuttle pin may even be centered completely so that the pump will continue to run at constant speed, without pumping any material, and without the need of a bypass or pressure relief valve.

Tri-Rotor’s Variable Volume Control Head Pump Models

Note that there is no Variable Volume Control Head option for the Series 40.

Typical Performance Curves for Tri-Rotor V-Head Pumps

Tri-Rotor Automatic Variable Volume Control V-Head Pump Typical Performance Curve

The pump, driven at a constant speed, establishes the discharge (or flow) rate.  The operator presets total pumping pressure by means of the control spring.  The pump then delivers at a constant value as long the operating pressure remains below the Automatic Pressure Response (“A-P-R”) point.

If pressure exceeds that point, a sensing mechanism inside the pump automatically responds by shortening the stroke of the pumping members, thereby, reducing the discharge rate until an equilibrium point (volume vs. pressure) is reached.

The pump stroke will continue to adjust proportionately in order to maintain maximum pressure in the discharge line.  In effect the pump is “freewheeling”, greatly reducing horsepower consumption and with little heat buildup.

The pump stroke will lengthen to resume a full discharge rate by simply reducing the pressure.

The sensing mechanism automatically responds to total pumping pressure in both suction and discharge lines.

If you have any questions about Tri-Rotor’s variable volume control head pumps, please contact us.