Basic Concerns with Ultrasonic Cleaning | Part 6: Watts per Gallon

It’s easy to assume that more power always delivers better results.  

But that’s not the case.  

While too little power can result in ineffective cleaning, too much power can lead to cavitation erosion and unnecessary energy costs. 

More power results in more vigorous cavitation and a stronger cleaning effect. This may be required for large, dense objects and items with heavy soiling or stubborn contaminants. High levels of power may harm delicate materials and fragile objects. In these cases, higher frequencies at lower power may be a better option. 

Applying the right level of power to an ultrasonic cleaner is key to efficient and effective cleaning.  

But it’s not straightforward. 

Determining the right amount of ultrasonic power for an application depends on a number of factors. 

The Ultrasonic Cleaning Tank 

Although larger tanks require more overall power than smaller ones, there’s an inverse relationship between watts per gallon and tank volume. 

For example, compare the size, power, and watts per gallon ratio for two of our ultrasonic cleaners: 

• 1.9 Gallon Bench Top Cleaner, 250 W, 132 watts per gallon  

• 204 Gallon Ultrasonic Cleaner, 4000 W, 20 watts per gallon 

The walls of a tank and the surface of the liquid absorb some of the energy that’s delivered to the ultrasonic bath. The total surface area of these surfaces in relation to the volume of liquid is greater in smaller tanks, leading to proportionally more energy loss than in larger tanks. 

In large tanks, ultrasound waves can travel unimpeded for greater distances and reflect cleanly off the surfaces. This enables the waves to last longer and create more cavitation bubbles, improving the efficiency of the cleaning process. 

In smaller tanks, ultrasound waves reflect more frequently and inefficiently from the surfaces. The ultrasonic energy dissipates more quickly, meaning that proportionally more power is required to achieve the same levels of cavitation. 

Transducer Positioning 

The positioning of transducers in a tank determines how the ultrasonic energy is distributed throughout the tank. Uniform distribution of waves is critical to achieving an efficient cleaning operation. 

It’s easier to position transducers in large tanks to ensure a uniform distribution of sound waves in the tank. It’s more challenging to achieve this distribution in smaller cleaners and those with a complex shape, such as a narrow tank. This means more power may be needed for efficient cleaning. 

Cleaning Load and Contaminants 

The objects to be cleaned and the contaminants to be removed also determine how much power is required for effective cleaning. 

Simple objects with a smaller surface area are easier to clean than complex objects with a large surface area, such as a heat exchanger with fins, or with complex geometries, such as blind holes and internal cavities. 

The type and amount of contaminant is another factor. For example: 
 

• Contaminants with lower solubility or that absorb greater amounts of ultrasonic energy need more power to remove them.  

• Buildups of contaminant on the surface or in hidden cavities are harder to remove – and require more power – than if there’s an even coating over the surface of the object. 

Other Factors

As we discuss in this series of blogs, many factors affect the results of ultrasonic cleaning. These include the cleaning cycle time, the temperature of the ultrasonic bath, the frequency of the ultrasound waves and the cleaning agent used. 

Increasing power may not necessarily deliver better cleaning – all the factors must be considered to find the combination that achieves the best results for each application.  

Manufacturers specify the power of an ultrasonic cleaner using average power, peak power, or both.  

Average power, sometimes referred to as RMS (Root Mean Square) power, is the continuous power at which a cleaner can operate safely over a prolonged period.  

Peak power is the maximum power that a cleaner can handle for short bursts without experiencing damage. It is usually double the average power and can’t be sustained over long periods. It’s important to know the peak power of a machine so that sudden power surges or spikes can be managed safely. 

Industrial and professional ultrasonic cleaners usually have the ability to vary the power level. This gives greater control over the cleaning process, enabling the optimum power level to be used for each application. 

Watts per gallon is a useful measurement for comparing ultrasonic cleaners and understanding their capabilities. It’s important to understand the factors that determine the best power level and watts per gallon ratio for your requirements.

If you have questions about your particular application, please feel free to get in touch so we can determine the right course of action for you. In addition, look out for the next post in this series in which we explore how the load being cleaned affects the ultrasonic cleaning process.

Ultrasonic Cleaners for Rent

We offer a range of our most popular ultrasonic cleaners for rent on a 30-day try-before-you-buy basis or as a long-term rental option.