Using a point switch for pump dry-running detection

Liquid at the tip is not proof of pump flow

A pipe pocket can remain wet while the pump lacks a reliable liquid supply. Foam may wet a sensor without providing acceptable suction. A closed valve, loss of prime or other pump condition may need separate detection.

Choose the sensor position with the pump and piping design in mind. The installation should represent the condition the protection function is intended to detect.

Review the electrical and control chain

The sensor normally provides a signal to a PLC or suitable interface. It does not directly switch a motor load. Define startup permissives, loss-of-liquid behavior, reset conditions and any restart limitation. Check that filtering does not allow an unacceptable dry-running interval.

Validate through an approved procedure

Test the process states and controller response with the responsible plant team. Follow safe isolation and test methods; do not deliberately run equipment dry without an approved test plan. If the protection has a safety-related role, assess the required architecture and documentation separately.

What to confirm for your application

• Pump and suction arrangement
• Residual liquid and foam at the location
• Required reaction and restart behavior
• Interface and load compatibility
• Other failure modes needing separate detection