Function of the float level controller

A float-type level controller is a liquid-level monitoring and control device designed based on the principle of buoyancy. Its primary function is to automatically detect changes in the liquid level within a container and, via switch signals, to start or stop actuators such as pumps and valves, thereby maintaining the liquid level within a set range. It is widely used in various industrial sectors, including marine applications, chemical processing, water treatment, environmental protection, and power generation.

I. Main Functions and Roles

Automatic Liquid Level Control
When the liquid level drops to the preset low point, the controller sends a signal to start the water pump or open the inlet valve; when the liquid level rises to the high point, water supply is automatically shut off. This process requires no manual intervention, achieving “automatic start on low water level and automatic stop on full water level.”

Application example: In ship bilge water, a float-level controller can automatically start the bilge pump to prevent excessive water accumulation from compromising navigational safety.

Multi-point Control and Alarm
By installing multiple float switches or employing a multi-contact design, three-level control—low-level warning, normal operation, and high-level alarm—can be achieved, thereby enhancing system safety and reliability.

For example, in chemical storage tanks, a low-level alarm is triggered when the liquid level is too low, and an overfill protection is activated when the level is too high, thereby preventing safety incidents.

Equipment Protection

Prevent damage caused by dry running of the water pump: When the water tank level is too low, promptly disconnect the power supply to avoid motor burnout due to no-load operation.
Prevent overflow incidents: promptly cut power and stop the pump at high levels to ensure site safety.

Adapting to Complex Operating Conditions

Corrosion-resistant materials (such as 304/316 stainless steel and PP plastic) are suitable for harsh media such as acidic and alkaline solutions and seawater.
Explosion-proof design is suitable for flammable and explosive environments, such as oil tank farms and natural gas processing stations.

Energy Conservation and Operational Efficiency Improvement
It requires no external power supply to drive the signal output (passive dry contact), features low power consumption and strong anti-interference capability, and boasts a simple structure and long service life, thereby significantly reducing maintenance costs.

II. Brief Description of the Operating Principle

The float-type level controller operates on the principle of Archimedes’ buoyancy and magnetic coupling technology:

Changes in the liquid level inside the container cause the float to rise and fall with the liquid surface, which in turn moves the built-in magnet, triggering the reed switch in the conduit to close or open. This generates a switching signal that controls the start/stop of the pump or valve via the control circuit.
The signal output is typically in the form of normally open (NO) or normally closed (NC) contacts, which can be connected to a PLC, a relay, or used to directly control the start and stop of a motor.

Note: During installation, avoid positioning the sensor near the inlet or the agitation zone to prevent false triggering caused by liquid level fluctuations. If the process medium contains ferromagnetic impurities, these may interfere with magnetic coupling; therefore, regular cleaning is required.