May 26, 2018

Effectiveness ultrasonic antifouling

  1. The effectiveness of ultrasonic antifouling

Shipsonic™ has invested considerable resources in developing systems with a guaranteed, consistent effectiveness.

Effectiveness of the ultrasonic antifouling system depends on 4 main factors;

  1. correct ultrasonic frequency
  2. sufficient ultrasonic energy
  3. correct transducer location
  4. optimal transducer design and fixation

Correct ultrasonic frequency

Our transducers are 100 Watts with a frequency of 28 KHz + – 0.5%. The variation of +/- 0,5 % means that each transducer has its own specific resonant frequency, which varies from the factory. Frequency also changes depending on the characteristics of the object on which the transducer is installed, with temperature and with method of installation. Hence, you can never foretell the frequency in which an object will vibrate, even if you know the characteristics of the transducer. Our design features a standalone software module for each transducer, looping constantly through all frequencies from 20 to 40 kHz. This enables us to ensure that each transducer/object combination always receives pulses in its optimum range. Secondly, the heavier transducers also have a lower frequency (28KHz + – 0.5%). It is known that the lower frequencies of the ultrasonic spectrum are more efficient.

Sufficient ultrasonic energy

We are one of the few, if not the only ones, who work standard with 100 Watt transducers. Moreover, our biggest control unit powers of such transducers. And, very straightforward; more transducers on an object means more ultrasonic energy means less fouling.

Correct transducer location

This is an acoustical problem, and acoustical problems are notoriously complex. As with all such problems, the solution is often a trial and error process.
To address this problem, Shipsonic is developing an ultrasonic signal strength measuring device. We develop this new device completely in-house. Once ready, the signal tester will use a contact microphone to measure ultrasonic energy levels in the steel of the object to be protected, while we have a magnetic device to temporarily place transducers on the sea chest or elsewhere. This way we can compare tester readings of different transducer locations and thus find the optimal locations for the transducers.

Transducer design and fixation

At Shipsonic we intentionally chose a PVC transducer housing, while this is not common in shipping. However, metal housings have too much mass compared to the mass of the transducer itself. These housings, therefore, absorb more energy, sometimes resulting in the housing cracking up. The mass of the metal housing also affects the resonant frequency of the transducer. The PVC housing of the transducer is not a way of cost-saving, but a conscious technical design choice. Within the PVC housing, the resonance element of the transducer can vibrate completely independent. With the water resistant model, the contact surface of the transducer is glued directly to the object to be protected, so no intermediate steel or artificial part of the housing gets in the way.

Transducer housing and fixation testing

 

 

 

 

 

 

Frequency and Energy testing

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