How does a magnetostrictive level transmitter measure liquid levels in petrochemical tanks?
1 Answer
A magnetostrictive level transmitter is a type of level measurement device used to measure liquid levels in petrochemical tanks. It relies on the principle of magnetostriction, which involves the interaction of a magnetic field with a ferromagnetic material. Here's how it works:
Waveguide: The level transmitter consists of a rigid waveguide, typically made of a ferromagnetic material like nickel-iron alloy. This waveguide is usually installed vertically along the inside of the tank.
Magnet and Electronics: At the top of the waveguide, there is a float or buoyant device containing a permanent magnet. As the liquid level in the tank changes, the float moves up or down the waveguide accordingly.
Current Pulse: An electrical pulse, usually in the form of a short current pulse, is sent down the waveguide. The pulse generates a magnetic field around the waveguide.
Interaction of Magnetic Fields: The magnetic field from the pulse interacts with the magnetic field of the float, causing it to slightly distort or deform. This deformation generates a mechanical stress wave that travels up and down the waveguide.
Time of Flight Measurement: Sensors along the waveguide detect the mechanical stress waves when they reach the top and bottom of the waveguide. The time it takes for the stress wave to travel from the top of the waveguide to the bottom and back is measured. This is known as the "time of flight" of the stress wave.
Calculating the Level: The transmitter's electronics measure the time of flight and use it to determine the distance between the top of the waveguide and the float. Since the float's position is directly related to the liquid level in the tank, the transmitter can accurately calculate the liquid level.
Output Signal: The level transmitter converts the liquid level measurement into an analog or digital output signal (e.g., 4-20mA, HART, Modbus, etc.) that can be sent to a control system or a display unit.
The magnetostrictive level transmitter offers several advantages, such as high accuracy, repeatability, and reliability. It is commonly used in various industries, including petrochemicals, due to its ability to measure liquid levels accurately and withstand harsh environments typically encountered in petrochemical tanks.
Waveguide: The level transmitter consists of a rigid waveguide, typically made of a ferromagnetic material like nickel-iron alloy. This waveguide is usually installed vertically along the inside of the tank.
Magnet and Electronics: At the top of the waveguide, there is a float or buoyant device containing a permanent magnet. As the liquid level in the tank changes, the float moves up or down the waveguide accordingly.
Current Pulse: An electrical pulse, usually in the form of a short current pulse, is sent down the waveguide. The pulse generates a magnetic field around the waveguide.
Interaction of Magnetic Fields: The magnetic field from the pulse interacts with the magnetic field of the float, causing it to slightly distort or deform. This deformation generates a mechanical stress wave that travels up and down the waveguide.
Time of Flight Measurement: Sensors along the waveguide detect the mechanical stress waves when they reach the top and bottom of the waveguide. The time it takes for the stress wave to travel from the top of the waveguide to the bottom and back is measured. This is known as the "time of flight" of the stress wave.
Calculating the Level: The transmitter's electronics measure the time of flight and use it to determine the distance between the top of the waveguide and the float. Since the float's position is directly related to the liquid level in the tank, the transmitter can accurately calculate the liquid level.
Output Signal: The level transmitter converts the liquid level measurement into an analog or digital output signal (e.g., 4-20mA, HART, Modbus, etc.) that can be sent to a control system or a display unit.
The magnetostrictive level transmitter offers several advantages, such as high accuracy, repeatability, and reliability. It is commonly used in various industries, including petrochemicals, due to its ability to measure liquid levels accurately and withstand harsh environments typically encountered in petrochemical tanks.