Walker Electronics Limited

Ultrasonic Cleaning
Frequently Asked Questions

The UK Leaders in Ultrasonic Cleaning Equipment.

Frequently Asked Questions

What is Ultrasonic cleaning?
The range of the human ear (depending on age) is about 16 Hertz to 16 kilo Hertz, Middle C is 216 Hertz, a grasshopper call around 7 kilo Hertz and a bat signal about 70 kilo Hertz.  Beyond human audible range is called 'ultrasonic'  An ultrasonic cleaner functions by containing an electronic 'generator' which develops a high frequency power.  The power is supplied to a piezo ceramic transducer which send sound waves into the tank.  These sound waves create millions of microscopic bubbles which collapse or implode releasing large amounts of energy and literally suck the contamination from the surface of the item being cleaned.  This process is called 'cavitation'
What is degassing and why should I do it?
Degassing is the removal of gases present in the cleaning solution. Mains water contains a surprising large amount of air. It is essential to remove this air before effective cleaning can take place, as 'useful' Cavitation will only occur after removal. Degassing is simply achieved by running the ultrasonic cleaner after the cleaning fluid has been changed.  The time taken to degas the solution depends on the size of the bath and the hardness of the water, however, when the fluid in the tank is degassed there is a noticeable increase in the "cold-boiling" action.  It is essential to degas AFTER the cleaning solution has been added as degassing will not take place easily in water alone.
Can ultrasonic cleaners damage small or brittle items?
With thousand of microscopic implosions every second you would have thought so. Ultrasonic cleaning is a very powerful way of removing contaminates from surfaces, however, the Cavitation is localised and at microscopic level. Care should be taken in choosing the correct cleaning medium - it's far more likely that this could damage the parts than the ultrasonic action. Most dental and medical instruments are perfectly safe, as are clock and watches, although hairsprings should be cleaned with caution and for a short time. Ultrasonic cleaners are not recommended for cleaning large gemstones, gemstones with faults or indeed any of the following: emerald, turquoise, malachite, opal, pearl and coral.
Why is a special cleaning solution required?
The contamination 'sticks' to the surface of an item. This adhesion needs to be broken. Water alone has no cleaning properties and is not sufficient to break down the bond. The most powerful ultrasonic cleaner will not work effectively without the proper cleaning solution; it is the interaction between the cleaning fluid and the cleaning tank that produces the results. Walker Electronics Ltd manufacture a wide range of cleaning solutions to suit most applications. For dental and surgical applications the Microbiology Advisory Committee reccomended the use of an "enyme detergent", such as WELzyme .
How often should I change the cleaning solution in my ultrasonic bath?
When cleaning medical and dental instruments it is good practice to change the fluid twice a day - 1st thing in the morning and then at lunchtime. The NDAC (National Dental Advisory Committee) and HTM0105  recommends changing the fluid every "4 hours or earlier if visibly soiled". With industrial applications there is no direct answer. It depends on so many factors: the level of contamination on the components being cleaned, how many times the fluid has been used etc. Suffice to say, change the fluid when there is a noticeable decrease in ultrasonic cleaning action or when the fluid is visibly dirty. For most application this will not be every time the machine is used. The fluid level should be maintained at the tank ridge level, as the system is tuned to this. Failure to use the correct solutions or not maintain the correct fluid level could result in poor cleaning results and may even cause damage to the ultrasonic cleaner.
How long should I clean an item for?
Another commonly asked question with no definitive answer! It will depend on the type of contamination, the quantity, the temperature of the cleaning fluid, how many items are in the unit, the type of cleaning fluid etc. If it's not clean, then clean it some more! With fresh cleaning fluid you should see the contamination being removed within the 1st few seconds. When you can see no more being removed, maybe it's clean! Inspect the item and if not happy re-clean, increasing the cleaning period next time.  Saying that we do recommend a 3 to 6-minute cycle is initially implemented for dental instruments.
What is the ‘Cavitational Heating System’?
When a Cavitation bubble implodes enormous amounts of energy is released into the cleaning solution. Walker Electronics limited have designed their ultrasonic cleaners to take full advantage of the heat generated, so much so that there was no need for additional heating elements to be fitted to their units. The obvious advantage here - if it hasn't got a heating element it can't go wrong! Some of our units will increase the temperature of the fluid by as much as one degree C. for every minute operated.
How many items can I place in my ultrasonic cleaner?
The more items that you place in your cleaning bath the less efficiently it will clean.  It is not advised to overlap items.  Always allow plenty of clear space between the items.
How can I test the efficacy of my ultrasonic tank?
There are 3 main ways of testing for ultrasonic agitation within the tank.  These are the protein residue test, foil test and the Brownes soil test. The foil test involves suspending strips of foil in locations throughout the tank and turning the machine on for 2 minutes.  When the foil strips are removed there should be noticeable denting, pitting and even perforations of the foil. Refer to Health Service Technical 01-05 for further details. Walker Electronics Ltd advice that this test is unnecessary to comply with HTM0105 providing the load check strips test AND protein residue tests are performed weekly. The Brownes soil test are plastic strips with have been contaminated to simulate the contamination found on surgical instruments.  Again the unit is operated but this time for a normal cycle length.  When the strips are removed from the tank there should be no or very little visible contamination present. The protein residue test work by, as the name suggests, testing for residue of protein on a surface after it has been cleaned.  The dirty instrument is cleaned as normal (normal length of time and normal cleaning solution) in the ultrasonic cleaner.  After cleaning the instrument is rinsed thoroughly and swabbed with the special kit.  A colour change of the fluid contained within the test vile from green to purple or grey indicates the presence of protein. Brownes soil test strips (load check stirps), protein residue test and standard HTM0105 test foil is available from Walker Electronics Ltd.