Mechanism of action of ultrasonic cleaning device - Capita selecta
Mechanism of action of ultrasonic cleaning device
Complex instruments that can not be reached sufficiently well by the rinsing water of the thermodisinfector will have to undergo treatment in an ultrasonic cleaning device beforehand, because this fulfills the function of a precision cleaner. You can think of complex (hollow) drills that are used in implantology. Furthermore, in case of a malfunction of the thermodisinfector (or if there is not yet available ...) the substitute manual cleaning will be supported with an ultrasonic cleaner.
The liquid in an ultrasonic cleaning device is vibrated by an ultrasonic transducer directly under the bucket of the ultrasonic cleaning device, which generates approximately 30,000 to 50,000 vibrations (Hertz) per second (30-50 kHz).
Such high-frequency vibrations cause alternating phases of high and low pressure in an aqueous liquid. At the low pressure, millions of very small vacuum cavities emerge, which are then compressed and imploded in the high-pressure phase. A lot of energy is released here. This process is called cavitation. With the energy released during the imploding of the cavities, dirt from the instrument sodium to be cleaned is released.
The water must be at rest when the ultrasonic cleaner is turned on. Water that is still in motion, because of the insertion of instruments, does not effectively guide the vibration, so that no cavitation can occur.
Higher temperature increases the effect of cavitation. At the start of ultrasonic cleaning, the temperature of the liquid should not, however, be higher than between 40 ° C and 45 ° C, because the temperature of the liquid automatically increases as a result of ultrasonic vibrations.
The liquid may ultimately not be warmer than 55 ° C, because at higher temperatures proteins will coagulate.
Fresh water contains a lot of dissolved gas (mostly ordinary air), which reduces the effectiveness of the ultrasonic cleaning device. Therefore, before use, the water must first be 'degassed' by allowing it to vibrate for 10 minutes without load. This creates so-called 'dead water', in which the ultrasonic vibration causes optimal cavitation.
With a correctly set frequency (35 kHz to a maximum of 50 kHz), suitable hardness of the water and correct concentration of the chemicals and the correct temperature, a vibration time of three to five minutes per load is sufficient.
For longer than three to five minutes under optimal conditions nothing adds.
In the stainless steel tray of the ultrasonic cleaning device, open-worked baskets or baskets can be used for the direct cleaning method. The instrumentation is then cleaned by means of cavitation by direct contact with the vibrating liquid.
In addition, closed beakers or glass bowls can be used for the indirect cleaning method. The cleaning liquid in such cups / dishes is then indirectly vibrated. This has the advantage that in an ultrasonic cleaning device at the same time different types of cleaning liquid and various types of small material can be cleaned.
CAUTION: never put a finger or hand into a working ultrasonic cleaning device, as it will cause serious tissue damage!
Hanging baskets, beakers and bowls must not touch the bottom of the cleaning device, as this will damage the bottom of the appliance. Baskets should therefore be supported on the sides of the ultrasonic cleaning device as a sort of frying basket, and beakers and bowls should be stored in a special rack so that they "float" in the liquid of the cleaning device.
A Basket not in contact with the soil. B Beaker not in contact with the bottom
The distance to the bottom should be about 2.5 to 3 cm for an effective vibration.
Substances that lower the surface tension of the water (detergent) simplify the release of the dirt. In addition, weak acids or weak bases can be added, depending on the type of material or the type of contamination. Usually, a disinfecting action is also required of the ultrasonic liquid. The concentration of the chemicals must be exactly measured, because changes therein negatively affect the cavitation process.
The following points must be observed when using an ultrasonic cleaning device:
- Tungsten carbide drills (implantology drills!) Must not be cleaned in a standard (acidic) ultrasonic fluid, because the carbon from the metal forms a bond with the acid. A special pH-neutral solution must then be used.
- Soft materials are unsuitable because they absorb the vibrational energy and thereby impede the cavitation.
- Hollow instruments must be 'launched' obliquely to prevent trapped air. They must also be positioned in such a way that the loosened dirt can be removed upwards from the instrument.
- Drills must be free from contact with other instruments, because they become blunt by rattling against each other. Placing in a drill block is the most common.
Drills in the drilling stand arranged and well manageable
- Always place a lid on a working ultrasonic cleaning device to limit the formation of contagious aerosol and to prevent noise nuisance caused by the sharp, high sound.