Lee Aiken is a level product marketing manager at MTS Sensors, a global leader in the development and production of magnetostrictive linear-position and liquid-level sensors. Based on MTS’ patented Temposonics® technology, the Sensors Division is continually developing new ways to apply magnetostrictive sensing technology to improve critical processing applications.

Aiken recently sat down with Chem.Info to discuss this technology and the positive impact it can have relating to wastewater management.

Q: What is a magnetostrictive sensor?

A: A magnetostrictive sensor is an instrument that takes advantage of the effects of electricity and magnetism on a specially designed udes a permanent magnet, electronics, the housing and the waveguide (specially designed alloy).

The waveguide is placed along the axis where the measurement would occur, and the permanent magnet is fixed to the moving part or housed i n a float on the liquid level. The electronics send a pulse down the waveguide that creates a magnetic field around the waveguide. The magnetic field of the waveguide interacts with the permanent magnet, and produces a torsional twist or strain pulse that propagates back to the electronics. The measurement is calculated based on a time-of-flight measurement from the release of the electronic pulse to the return of the strain pulse. The result is a highly accurate and repeatable measurement.

Q: How can it be used in water and wastewater treatment applications?

A: A magnetostrictive transmitter can be used in water and wastewater treatment applications by adjusting the housing in which it is contained. For these applications, a standard offering of rigid pipe made from 316L stainless steel or Hastelloy-C, or a flexible hose made from 316L stainless steel, would protect the waveguide that is submersed in the vessel.

Along with the pipe, a specially weighted float would be installed on the pipe or hose to contain the permanent magnet in either 316L stainless steel or Hastelloy-C. A housing is attached to the top of the pipe to protect the electronics and for conduit connections. For use with specialty applications, custom metals can additionally be custom ordered.

Once the magnetostrictive sensor is placed in the correct housing for water and wastewater treatment applications, it can be used for chemical tanks, sumps, bio-waste holding and treatment tanks, secondary clarifiers and just about any situation requiring accurate level measurement. Magnetostrictive sensors do not have any special requirement for installation that limits their applications. Installation is as simple as a mounting point away from inlets and outlets.

Q: What is the main benefit of using a magnetostrictive sensor for liquid-level measurement in such applications?

A: There are several benefits of using a Level Plus® liquid-level sensor, including high accuracy, ease of installation, the ability to be repaired in the field, a flexible transmitter, free configuration software, volume measurement and three-in-one measurement of the product, interface and temperature.

However, the main benefit for the water and wastewater industry is that Level Plus liquid-level transmitters are not affected by changes in environmental conditions. Changes in dielectric constants, temperature and vapors, or the presence of foam, do not degrade the performance of these transmitters.

Q: What advantage does magnetostrictive technology have over ultrasonic technology in water or wastewater treatment applications?

A: The advantage of magnetostriction over ultrasonic technologies is that magnetostriction is not affected by foaming. The magnetostrictive float can sink through the foam, and accurately and repeatedly register the liquid level, not the foam level. The ultrasonic gauge has a propensity to read the foam level that is on top of the liquid level. This can create major problems for the wastewater treatment facility operators trying to maximize efficiency and maintain regulatory compliance.

Q: Are there circumstances in which a magnetostrictive sensor should not be used? If so, what sh d be used instead?

A: There are instances in which a level technology is better, and in which it is only second best. Really, the only time that magnetostrictive sensors are second best is when there is debris in the tank or when the liquid is highly cohesive. In either of these cases, there is the risk that the float can become lodged due to the particulate matter or the cohesiveness of the liquid.

An example of this is in the primary clarification and sludge tanks. These clarifiers/tanks typically have debris entrained in the waste product, such as large pieces of wood, clothing, rags and other undesirable material that can clog floats. The best bet is to go with a radar-based unit, which does not get clogged, but I would stay away from guided wave radar due to the debris. n
For more information on MTS Sensors and level sensing, please contact Lee Aiken, MTS Sensors level product marketing manager, at lee.aiken@mts.com or visit www.mtssensors.com.
MTS Sensors
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