How to Select Ultrasonic Frequency and Ultrasonic Power

TI-H Ultrasonic Cleaner and Control Panel
Elma TI-H Ultrasonic Cleaner and Control Panel

Ultrasonic cleaner manufacturing is experiencing sustained growth according to a recent report by industry research publisher IBISWorld.  While the report focuses on ultrasound as the dominant method used for cleaning medical and dental equipment, a takeaway is that companies in many industries are looking at the technology as an environmentally friendly way to remove contamination from surfaces that can be safely wetted in a biodegradable water-based ultrasonic cleaning solution. 

When you select an ultrasonic cleaner, whether tabletop or industrial-sized, you must make decisions in addition to cleaning solution capacity.  Two have to do with ultrasonic frequency and ultrasonic power. 

How to Specify Ultrasonic Frequency

Ultrasonic frequency is measured in thousands of cycles per second (kilohertz or kHz).  Frequencies are generated by ultrasound transducers affixed to the bottom, and in some cases also the sides, of the ultrasonic cleaning solution tank.  The transducers are excited by the unit’s ultrasonic generator to produce millions of microscopic bubbles in the solution that implode on contact with parts being cleaned.  The implosion, called cavitation, removes contamination faster and more thoroughly than mechanical scrubbing using wash tanks or aerosol sprays.

Ultrasonic frequency also determines cavitation bubble size.  Low frequencies such as 25 kHz produce relatively large bubbles that implode more violently than those created at higher frequencies that produce comparatively gentle cleaning action.  Visually the size is virtually impossible to distinguish.  For example a 25 kHz bubble has about 3 times the approximately 40 micron radius of 80 kHz. 

So, what does this mean?  If you are removing gross contaminants from robust parts such as fabricated or cast metals specify a lower frequency ultrasonic cleaner.  Softer metals, plastics, and products with polished surfaces should be cleaned at higher frequencies. The smaller bubbles are less likely to cause surface damage.  They are also better able to penetrate tight areas such as seams, crevices and blind holes.

If you are cleaning a variety of products consider a dual-frequency ultrasonic cleaner.  An example is the Elmasonic TI-H line available from Tovatech offered in either 25/45 or 35/130 kHz frequencies.  Another is the Elmasonic P series that operates at 37 or 80 kHz.

The Role of Ultrasonic Power

Power has several definitions when discussing ultrasonic cleaning and is described in different ways by equipment manufacturers.  In terms of cleaning power it is calculated as the power delivered to the transducers and expressed as watts per gallon (or liter) of cleaning solution.  Most cleaners operate at 50 to 100 watts per gallon. 

As power increases so does the number of bubbles, so increased power yields faster cleaning action but only up to a point.  Beyond that you are not only wasting energy you also risk damaging parts being cleaned.

Another definition is total power or the amount needed to drive everything in the unit including ultrasonic generators and heaters (if supplied).  It should not be confused with ultrasonic power. 

Peak power is defined as the ultrasonic power generated at the peak of the sound wave and can equal 2, 4 or 8 times the average power.

Variable ultrasonic power is offered on certain units such as the Elmasonic TI-H and P series mentioned above.  Another useful feature on the P series is a pulse mode that provides bursts of power to remove tenacious contaminants.

This post does not answer all questions on ultrasonic frequency and power but should give you an idea of the importance of these features when purchasing an ultrasonic cleaner.  The professionals at Tovatech are available to guide you through the process and to recommend the correct equipment for your requirements.

About Rachel Kohn

So how did an MIT Ph.D. end up selling refrigerators? When I figured out that a lot more scientists buy lab refrigerators than innovative leading-edge instruments. I hope that my many years of lab experience will help you find the right equipment for your work. Before co-founding Tovatech I worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health, and Hoechst Celanese. And before that I spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks, and polysaccharides. Some day, eventually, I’ll make enough money to develop an innovative technology that will change the world. Read More