A servo tank gauge, also known as a servo level gauge or servo level transmitter, is a device used for accurately measuring the level of liquids in storage tanks, such as those used in the petroleum, chemical, and industrial sectors. It operates based on the principle of hydrostatic pressure and typically consists of several key components:
- Sensor Tube: The sensor tube is a hollow metal tube that extends from the top of the tank to the bottom, or to the desired level measurement point within the tank. It is open at the bottom end to allow the liquid to enter the tube.
- Float: Inside the sensor tube, there is a float that moves up and down with the liquid level. The float is typically buoyant and made of a material like stainless steel.
- Displacer: Attached to the float is a displacer, which is often a metal rod or cylinder. The displacer is denser than the liquid being measured, so it displaces an amount of liquid equal to its own weight.
- Pulley System: The servo tank gauge includes a pulley system, which is connected to the displacer and the float. As the liquid level in the tank rises or falls, the float and displacer move accordingly.
- Sensor/Transmitter: At the top of the sensor tube, there is a sensor or transmitter that measures the position of the float and displacer. This sensor is usually based on technologies like magnetostrictive, capacitance, or other position-sensing methods.
Here’s how a servo tank gauge works:
- Initial Calibration: The servo tank gauge is calibrated to the specific tank it is installed in. This calibration determines the relationship between the position of the float and the liquid level in the tank.
- Level Measurement: As the liquid level in the tank changes, the float and displacer move up or down inside the sensor tube. This movement is transmitted through the pulley system to the sensor/transmitter.
- Position Sensing: The sensor/transmitter measures the precise position of the float and displacer within the sensor tube. This information is converted into a level measurement.
- Output Signal: The level measurement is then sent as an output signal to a display or control system, where it can be monitored and used for various purposes, such as inventory management, process control, or safety monitoring.
- Continuous Monitoring: The servo tank gauge provides continuous and real-time level monitoring, allowing operators to keep track of the liquid level inside the tank and take appropriate actions as needed.
Servo tank gauges are known for their accuracy and reliability in measuring liquid levels, making them essential tools in industries where precise level control and monitoring are critical.