Screw valve selection: balancing viscosity, volume and accuracy

A screw valve is a positive-displacement metering device: volume is set by rotation, so viscosity and target volume come before price.

First, viscosity range. Medium-to-high viscosity and particle-filled fluids suit a screw structure, but the flow path and rotor/stator clearance must match the viscosity band — otherwise the valve may starve or fluctuate.

Second, shot volume. The smaller the volume, the higher the demand on rotor/stator fit and drive resolution. The same model behaves differently at small and large volumes, so confirm the actual process window.

Third, drive and control. Stepper drives cost less; servo drives offer better low-speed stability and speed range. If the machine changes acceleration and volume profiles frequently, servo is the better choice.

Share fluid brand and model, viscosity, target volume and cycle time — a matching model can usually be identified in one conversation.