Four steps to tell you what is ultrasonic power and how to choose.
Four steps to tell you what is ultrasonic power and how to choose.
STEP.1 What is ultrasoic power?
In general, we add the power of every ultrasonic transducer togather to caculate the ultrasonic cleaning system.so we can say the ultrasonic transducers supply the ultrasonic energy.
STEP.2 Four influencing factors of ultrasonic power
In the practics, it isn’t that simple.it have many factors must be considered in determining what amount of ultrasonic power will be appropriate for a specific application in a specific setting.
1) Process Parameter Requirements
Chemical and concentration
Typical cleaning time required
2) The Tank Volume and Shape
Volume – Cubic measure or gallons
Shape – Length, Width and Depth
Cleaning zone – Parts placement and racking
Internal features – Heaters, Agitators, Linings, Submersible Pumps, etc.
3）The Contaminant Being Removed
Removal difficulty – Light oil, buffing compound
Thickness of buildup – Holes plugged solid vs. surface coat
Solubility of the contaminant and its ability to absorb ultrasound – a thin coating of light oil vs. a thick coating of heavy grease
4）The Characteristics of the Parts Being Cleaned
Size – Physical dimensions
Weight – Weight/Density
Number of parts per load or per unit of time – Parts per rack or basket, parts per hour Complexity of Cleaning – Holes, blind holes, internal surfaces, hems, etc.
Ratio of part surface area to part size – A solid cube, for example, has less surface area per unit of volume than does a typical heat exchanger which is purposely designed to have a very large surface area relative to its mass to provide maximum heat transfer.
STEP.3 HOW TO CHOOSING THE ULTRASONIC POWER
1) watts per volume/gallon
Fist,we must have adequate power to initiate and maintain cavitation under most work conditions.For water at ambient temperature the minimum amount of energy needed to achieve cavitation was estimated to be 0.3 to 0.5 watts per square centimeter for the transducer-radiating surface operating at 40 KHz.
If we try to introduce too much ultrasonic power into a tank a barrier will form at the liquid/radiating surface interface that will block additional input power and will cause advanced cavitation erosion.
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. A low power level will also greatly reduce the cleaning applications the tank will be able to perform.
So,Ultrasonic energy is usually specified in watts per square centimeter. (0.3 to 0.5 watts per square centimeter) Very simply, the total ultrasonic power delivered to the tank is divided by the number of volume of liquid the tank contains to arrive at this number.Although it is not sufficient without considering a number of other factors,it was stated earlier that the measure of watts per volume in a cleaning tank.
2) other factors
The greater the load in a tank, the more power will be required. A system used to clean small parts such as jewelry,watch or fork. this will be required less ultrasonic power than the same size system used to clean printer,metal or bearing weighing 10 pounds each. The key factors here are the weight of the parts and the number being cleaned at one time. A heavily loaded tank may require up to several times the power of one with a lower loading factor.
Simple iterms are easiest to clean because they only have a little surface area.
As complexity grows, effective cleaning requires a higher ultrasonic intensity.Blind holes and internal cavities provide the first level of complexity and may require an increase in power over the level required for the simplest of iterms.
As the ratio of surface area to volume increases,the cleaning becomes much more difficult. We need to require up to several times more power than the simplest iterms or use the heater function to elevate the temperatuer
——Transducer Distribution:The ultrasonic transducers must be properly arranged to provide uniform ultrasonic density.
——Tank Design and Construction:In some instances, if the cleaning tan was too deep,some designer will add the ultrasonic transducers on the two side of the tank to increase the ultrasonic energy.
If a person is not familiar with ultrasonic activity and power levels and considering purchasing a special ultrasonic cleaning system for a specific cleaning application.we recommend as follow:
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.
STEP.4 What exactly means “watts per volume/gallon”?
To determine if we have adequate ultrasonic power in a tank we must know both the wattage per square inch of the transducer-radiating surface and the cubic volume measurement of the liquid being ultrasonically activated.
The Ultrasonic cleaner have different ultrasonic power intensity: low intensity, medium intensity, standard intensity, and high intensity.so we can throught some cases below to explain their principles for you.
we take the ps-30a 6l Mechanical ultrasonic cleaner as example:
The ultrasonic cleaning tank bottom measures 12 inch by 4.5 inch this would give us a radiating surface of 54 square inch. This tank were driven by a 180-watt generator ,So the watt density would be 3.3 watts per square inch (180-divided by 54) on the radiating surface.
1) standard intensity
If we fill this 12 by 4.5-inch tank to a depth of 9 inch we will now have 486 cubic inches of liquid.If a 180-watt generator drives this tank the volume density would be 0.37 watts per Cubic inch of liquid. This would be considered a standard intensity ultrasonic tank.
2) high intensity
If we now install a 360 watt generator to drive this tank the watt density per square inch on the Radiating surface would be 6.6 watts per square inch on the radiating surface and 0.74 watts per cubic inch of liquid; this would be considered a high intensity ultrasound tank.
3) low intensity
Now lets take this 12-inch by 4.5 ultrasound tank and increase is volume by filling it to up to a depth of 36 inches. If this tank is once again connected to a 180-watt generator the watt density is again 3.7 watts per square inch, but the watt density has became 0.093 watts per cubic inch .
The generator may have enough power to initiate cavitation in the first or second wave length but will loose amplitude as it travels through this much liquid and will have trouble initiating and maintaining cavitation in the remainder of the tank.
The only way to solove this problem—-Elevate the tank temperature.
At the elevated temperature of 180 degrees Fahrenheit the tank will eventually degas and cavitation will be initiated. The precaution that must be taken with this tank is that the high temperature must be retained and the load being cleaned must be kept small or the tank will stall and cavitation will be lost.