October 9, 2019
Ever wanted to know what an ultrasonic cleaner look like on the inside?
I received a call one morning from a dental practice with a concern about their bench top ultrasonic cleaner.
Their ultrasonic cleaner had failed its morning performance test and they wanted to know what they should now do. They had run the al foil test twice and it had failed both times.
The al foil test uses 3 pieces of aluminium foil draped over bamboo sticks that are spread evenly through the tank. The cleaner is then run for 10 seconds.
Two pieces of al foil had even dimples and perforations, while the last piece was no where near as dimpled and perforated.
This confirmed that the cleaner wasn’t working correctly and would not be able to clean the instruments effectively.
Quite possibly a transducer failure, I advised them to put an out-of-order sign on the cleaner – or remove it altogether from the sterilisation room – and send it off to be fixed.
What’s a transducer?
In my last article (part 1), I explained that the ultrasonic cleaner cleans instruments by sending sound waves through the water/detergent solution which causes the cavitation process (or cleaning process).
How do we know each transducer is working properly? Turns out there aren’t any lights or gauges on outside to tell us. So, we must perform a test (called a performance test) every day to test the ultrasonic cleaner’s cleaning ability*. i.e. How well the transducers are working.
I’ll discuss the various types of performance tests in another article, soon to be written!
What does a transducer look like?
Naturally curious about the inner workings of the machine, I was able to secure a discarded ultrasonic cleaner which I could disassemble.
I found a couple of metal plates attached to the bottom of the tank, each with a couple of wires leading to a circuit board.
The 2 metal plates are the transducers. Once the power is switched on, these transducers vibrate really fast and cause sound waves to move through the liquid in the tank and produce millions of microscopic vacuum bubbles. As each bubble forms, it gets too big and collapses causing shockwaves to ‘shake off’ the dirt and contamination.
A simple machine, but very effective.
- Infection Control