Major and the most expensive unit of any acoustic antiscale device is a magnetostrictive transducer (also known as ultrasonic emitter). Ultrasonic transducer converts electromagnetic waves into mechanical ultrasound vibrations and transmits them to heat-exchange equipment that needs to be protected against scale.
Inside the transducer has the magnetostrictive core that changes its size when exposed to electric current passing through the core coil. The core is soldered to a steel contact which is welded to the equipment that needs to be protected.
18-25 kHz supersonic frequency electrical impulses are sent from generator to transducer through cables. This electrical signal is transduced by magnetostrictive core into mechanical vibration having the same frequency. Since the transducer and the protected equipment are welded together making a single unit, ultrasonic vibration is induced across the whole structure of heat-exchanger or boiler thus spreading over the whole exchange surface and reemitted into water. Thus, continuous micro vibration with the amplitude of several microns, safe for welding and folding but destructive for calcium carbonate and other solid deposits, occurs in metal.
Construction of magnetostrictive transducer is a complicated and expensive process that needs considerable technological input, especially when permendur is used as magnetostrictive material. Permendur is a cobalt-iron-vanadium alloy with excellent magnetostrictive properties used in manufacturing of acoustic antiscale device «Acoustic-T». Magnetostrictive transducers are not only complicated devices but also use powerful current signal for excitation which needs relatively powerful generator reducing the length of connection cable to 8m max.
The question is: Why can’t we use piezoceramic transducers in anti-scale devices? Global market gives us a wide choice of piezoceramics. Piezoceramic transducers are relatively cheap, compact and are excited by voltage signal instead of current signal, which allows any length of cable from generator to ultrasonic source. The thing is that the vibration amplitude transmitted by piezoceramic transducers strongly depends on the attached load. It is the physical property of piezoceramics, and nothing can be done about that. Piezoceramic transducers working for large attached load barely transmit acoustic energy to load. For that reason, magnetostrictive transducers are highly effective for inducing ultrasonic vibration in massively large structures, such as tube-and-shell heat exchangers and boilers. Piezoceramic ultrasonic sources can be used for anti-scale protection of plate heat exchangers (that’s what we actually do with Acoustic-T PC devices).
Magnetostrictive and piezoceramic ultrasonic transducers
Until quite recently we used to operate PMSI-3 series transducers having this specific perforated body that you can see in photos on our website. PMSI-3 transducers were substituted by brand-new improved TMS-30 transducers that used in acoustic anti-scale device Acoustic-T starting from 2015.
Base specifications of PMSI-3 and TMS-30 are similar being ideal for scale prevention. Resonant frequency of both transducers is 22 kHz with electric power demand of 100 W. However, TMS-30 compared to PMSI-3 is more functionally accomplished and effective for transduction of electrical signal into ultrasonic signal, which becomes clearer and has no spurious emissions. TMS-30 has a higher operating temperature of 220°С (compared to that of PMSI-3: 180°С). A longer and thinner arrowhead of TMS-30 facilitates welding of ultrasonic generator to the protected equipment.
Magnetostrictive transducers PMSI-3 (in the center) and TMS-30
| Cross-sectional area of magnetostrictive package | 9 cm2 |
| Curie temperature | 950°C |
| Voltage | 500…600 V |
| Working frequency | 18…26 kHz |
| Maximum allowable electric power | 100 W |
| Diameter of the ultrasonic tool | 25 mm |
| Waveguide material | AISI 1020 |
| Weight | 2,2 kg |
| Dimension | ⌀60 x 275 mm |
| Cooling | Aerial |
| Mode of operation | streaming |
| Service life minimum | 12 years |
| Maximum working temperature as standard | +220°C |
| Maximum working temperature as special | +300°C |
Besides, we have created a unique 180 W TMS-40 transducer having an increased magnetostrictive capacity. Its power is excessive for anti-scale protection and it can be used in process flows such as ultrasonic cleaning and others.
TMS-40 (left) и TMS-30 (right)
Magnetostrictive packages of transducers. TMS-40 (left) and TMS-30 (right)
| Cross-sectional area of magnetostrictive package | 16 cm2 |
| Curie temperature | 950°C |
| Voltage | 500…600 V |
| Working frequency | 18…26 kHz |
| Maximum allowable electric power | 180 W |
| Diameter of the ultrasonic tool | 25 mm |
| Waveguide material | AISI 1020 |
| Weight | 2,7 kg |
| Dimension | ⌀65 x 265 mm |
| Cooling | Aerial |
| Mode of operation | streaming |
| Service life minimum | 12 years |
| Maximum working temperature as standard | +220°C |
| Maximum working temperature as special | +300°C |