Determining Ultrasonic Power

 To determine the ultrasonic power in a tank one must know both the wattage per square inch of the transducer-radiating surface and the cubic volume measurement of the liquid being ultrasonically activated.


  For example, if the ultrasonic tank bottom measures 10 by 14 inches this would give us a radiating surface of 140 sq. inches.   If this tank were driven by a 500-watt generator the watt density would be 3.6 watts per square inch (500/140) on the radiating surface.  If we fill this same 10 by 14-inch tank to a depth of 10 inch we would now have 1400 cubic inches of liquid with only .36 watts per inch3 of liquid. This would be considered a standard intensity ultrasonic tank.

   If we now install a 1000 watt generator to drive this tank the watt density per square inch on the radiating surface would be 7.2 watts per square inch on the radiating surface and .72 watts per cubic inch of liquid; this would be considered a high intensity ultrasonic tank.

   Now lets take this 10-by 14 inch tank and increase is volume by filling it up to a depth of 36 inches. (22 gallon). If this tank is once again connected to a 500-watt generator the watt density is again 3.6watts per square inch, but the watt density per cubic inch has dropped from .36 watts per cubic inch to (.099 ) watts per cubic inch. This is a reduction from 1/3 watt per cubic inch to 1/10 watt per cubic inch of liquid. The generator may have enough power to initiate cavitation in the first or second wavelength but will loose amplitude as it travels through this much liquid and will have trouble initiating and maintaining cavitation in the rest of the tank.  In this situation, cavitation could be achieved by raising the liquid temperature to 180 degrees.  

   Ultrasonic power may be rated as low, medium, standard or high intensity. It should be obvious that we can not expect to use the same ultrasonic power level as used in the blind cleaner, (usually in the area of 1500 watts for 25 to 30 gallons) and expect to install this same amount of power into a tank containing 95 or 100 gallons and expect to achieve effective ultrasonic cleaning.

  A person unfamiliar with ultrasonic activity and power levels may therefore be deceived as follows:
     1) Thinking things are working the way it should,  
    
2)
Believing the cleaning task is too difficult
     3) Having a load which is too large for the tank,  
    4) Believing I must be using the wrong chemical(s).

   As the capacity of an ultrasonic tank increases, the increase in ultrasonic power is not linear. If we drive a 10-gallon tank with 750 watts of power we do not have to drive a 90-gallon tank with 6750 watts of power to archive the same cleaning results. For instance, if we change the configuration of a tank but retain the same volume the ultrasonic power requirements may also change.  A tank with dimensions of 24 x 24 x 9 inches deep (22 gallon) may only require 750 watts of ultrasonic power where a tank with dimensions of 12 x 12 x 36 inches deep (22 gallon)may require 1500 watts of ultrasonic power to achieve the same cleaning results.

   Whether one is blind cleaning, doing fire restoration or considering any other type of ultrasonic cleaning these things are good to know.  A qualified ultrasonic design engineer will be able to design a tank appropriate to any special cleaning needs that one may have.

 

   

ULTRASONIC POWER CONSIDERATIONS:

1) Adequate power must exist to initiate and maintain cavitation under most work conditions.

2 Introducing too much ultrasonic power into a tank actually creates a barrier at the liquid/radiating surface interface that will block additional input power and cause advanced cavitation erosion.

3 If we do not have adequate ultrasonic power initiating cavitation will be difficult, maintaining cavitation will be difficult, and cleaning at best will be marginal.

4) Degassing.  Removal of unwanted gas from the liquid must be completed before cavitation can be fully effective.

5) When considering purchasing a special ultrasonic cleaning system for a specific cleaning application FIRST Contact someone who is knowledgeable in ultrasonic design. SECOND. Send a sample of the item to be cleaned to their testing lab for evaluation. THIRD. Request information on tank design best suited for the application.

 

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