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Ultrasonic cleaner for medical instruments - functionality, use & advantages

Ultrasonic cleaning is an important preparatory step in the reprocessing of medical instruments. The process is used to effectively remove adhering organic and inorganic residues before thermal disinfection and sterilisation take place.

The operating principle of ultrasonic cleaners is based on cavitation: high-frequency sound waves generate microscopic vacuum bubbles in the cleaning fluid, whose implosions detach the impurities from the instrument surface.

Medical ultrasonic cleaners are specially designed for material compatibility and process validation. The reproducible and residue-free cleaning of medical instruments is the basic prerequisite for the effectiveness of all subsequent disinfection and sterilisation processes and ensures compliance with hygiene regulations.

Why ultrasonic cleaners are indispensable for medical instruments

Ultrasonic cleaning is indispensable in the medical environment as it is able to remove deposits in the smallest crevices, joints and lumens where manual methods such as brushes or spray nozzles cannot reach. In the medical field, where instruments are contaminated with blood, tissue residues and saliva, cleaning must be reproducible, thorough and gentle on the material. If this is not done, subsequent disinfection and sterilisation would be ineffective - resulting in so-called „sterile dirt“.

Authorities such as the RKI recommend automated procedures. Ultrasound is considered state of the art in clinics and surgeries because it makes a decisive contribution to process reliability:

How ultrasonic cleaning works: Cavitation, frequency & power

Ultrasonic cleaning of medical instruments is based on the cavitation principle. Sound waves create tiny bubbles in the liquid. When these bubbles implode, microscopic currents and forces are released. These detach dirt particles from the instrument surface and remove deposits from even the finest recesses.

Ultrasound is the „mechanics“ of the process. The actual removal of the deposits is carried out using customised chemical cleaning agents. The interplay of cavitation and chemicals ensures uniform, deep cleaning even in inaccessible areas.

Frequency and power

The power density (power per litre) and extremely precisely manufactured transducers, which ensure even sound distribution, are decisive for the cleaning effect. Only an evenly distributed power ensures that cavitation bubbles are created throughout the tank and that complex, highly loaded screens are reliably cleaned.

- Too little power leads to insufficient cavitation.
- Oversized, poorly managed power can put unnecessary strain on materials.

The frequency (e.g. 35-45 kHz) is also important in order to find the optimum balance between intensity and gentleness. Lower frequencies produce a stronger cleaning effect, while higher frequencies enable gentler processes for sensitive materials.

The power density

The power density describes the concentrated ultrasonic energy per volume in the cleaning fluid. It is decisive for the intensity of the cleaning effect.

- Intensity of cavitation: A sufficiently high power density ensures that the cavitation bubbles implode powerfully enough to reliably detach dried organic residues (blood, tissue) from the instrument surface.
- Reproducibility: When comparing ultrasonic baths of different sizes or manufacturers, users must consider the power density. If the power density in a large bath (e.g. 10 watts per litre) is much lower than in a small bath (e.g. 50 watts per litre), the intensity may not be sufficient to achieve the same cleaning quality.

The sounders

For thorough cleaning of medical instruments, it is not enough just to have a high total output. The power must be distributed evenly throughout the entire tank to ensure complete cleaning.

- Homogeneous sound field: Precisely manufactured sound generators and a precisely harmonised tank geometry create a uniform sound profile throughout the pool. Technologies such as SWEEP technology are used to ensure a homogeneous sound field.
- Complete cleaning: Only when the power is evenly distributed do cavitation bubbles form at every point in the bath, reaching all instruments and their complex geometries.
- Cleaning batches: This even distribution is particularly important when sieves or high batch volumes need to be cleaned. If the sound distribution is uneven, parts of the load or certain instruments in the meshes of the trays would not be sufficiently cleaned, which would make subsequent disinfection and sterilisation ineffective.

Which medical instruments are suitable for ultrasonic cleaning

Ultrasonic cleaners are able to fulfil the cleaning requirements for a wide range of medical devices that require gentle but deep cleaning due to their geometry or material properties.

The following medical instruments benefit from ultrasonic cleaning:

Surgical instruments: standard stainless steel instruments, surgical instruments in general and implant instruments.
Minimally invasive instruments (MIS): Instruments with long, thin lumens and complex geometries.
Robotic instruments: Highly complex instruments that are virtually impossible to clean reliably by hand.
Dental instruments: scalers, probes, forceps, drills, NiTi files, dentures and impression trays.
Laboratory glassware: Glass vessels and similar accessories.

The following are not suitable for ultrasonic cleaning:

Step-by-step: Using an ultrasonic cleaner in the medical reprocessing process

The ultrasonic cleaner is an elementary component of the reprocessing chain, which follows the KRINKO/RKI recommendations and provides for the strict separation of cleaning, disinfection and sterilisation.

Integration into the process

Ultrasonic cleaning is always the first step in reprocessing. Pre-cleaning must be carried out promptly after use to prevent blood and tissue from drying out.

The typical reprocessing process for medical instruments is as follows (simplified illustration, additional steps may be required):

1. Pre-cleaning in an ultrasonic bath

Instruments are placed in suitable baskets or trays and operated in the bath with the correct cleaning medium (chemicals, concentration, temperature).

2. Rinse off

After sonication, the instruments must be thoroughly rinsed with water to remove chemical residues.

3. Thermal disinfection

The instruments go into the washer-disinfector for thermal disinfection at around 95 °C.

4. Inspection, care, drying

This is followed by a visual inspection for cleanliness and function, care and drying.

5. Packaging and sterilisation

The instruments are packaged and sterilised in a steam steriliser at 134 °C.

Device and equipment features for professional ultrasonic cleaners

A high-quality medical ultrasonic cleaner must offer durability, robustness and precision for continuous operation.

Quality features and vertical integration

Professional ultrasonic cleaners are characterised by the following features:

Robust stainless steel trays: They are welded, resistant to chemicals and seal-free in the seam area.
Hygienic design: trays with rounded corners make it easier to clean the appliance itself and prevent dirt accumulation.
Durability: The construction must be designed for decades of continuous operation. Users report devices that run reliably for 20 to 30 years.
Technology: High-quality materials such as special ceramics for transducers and precise coordination of the ultrasonic field and tank geometry ensure uniform performance and consistent cleaning results.

Controls and accessories

Operating elements on ultrasonic cleaners for medical instruments range from simple rotary knobs to touch displays with programme storage and process documentation (e.g. Smart series).

Suitable accessories tailored to the respective cleaning purpose are essential for hygienic and instrument-appropriate cleaning:

The correctly selected accessories ensure that the ultrasound and cleaning fluid can reach all relevant surfaces and that nothing slides around in the tank.

Cleaning chemicals in the ultrasonic bath: requirements & selection criteria

The cleaning medium is of crucial importance for the effectiveness of ultrasonic cleaning. Pure water cleaning alone is not sufficient, as it does not adequately remove dried residues such as blood, tissue or saliva. Cavitation, i.e. the formation and implosion of vapour bubbles in the ultrasonic bath, is therefore dependent on the support of chemical agents.

Cleaning agents tailored to the type of soiling are required, the effect of which is intensified by ultrasound. For this purpose, BANDELIN offers enzymatic or surfactant-based products that reliably remove organic and inorganic soiling. A distinction is made between pure cleaning preparations (e.g. TICKOMED 1, STAMMOPUR R) and combination preparations with an additional, albeit only partial, disinfecting effect (STAMMOPUR DR 8, STAMMOPUR 24). The latter serve to protect the user, but never replace the necessary thermal disinfection.

When selecting suitable chemicals, material compatibility must always be taken into account in order to avoid corrosion and surface damage to the medical instruments.

Common errors in the ultrasonic cleaning of medical instruments

Compliance with the correct process steps is crucial for hygiene safety. Common errors that jeopardise the effectiveness of reprocessing include

Incorrect categorisation of the ultrasonic bath:

As things stand today, classic disinfection in the ultrasonic bath is not permitted. The bath is clearly assigned to cleaning or pre-cleaning. Disinfection must be carried out thermally in the washer-disinfector.

Use of pure water:

Pure water without suitable chemicals leads to inadequate results, as organic residues are hardly removed.

Wrong / too aggressive chemistry:

Unsuitable or incorrectly dosed agents can damage instruments or reduce the cleaning performance.

Too short sonication times:

There must be sufficient time to completely remove all residues.

Overloading the baskets:

If the basket is overloaded, the sound distribution is disturbed.

Unsuitable instruments:

Optics, flexible endoscopes and electrical instruments must not be cleaned in an ultrasonic bath.

These errors can be avoided through clear written work instructions, manufacturer-compliant chemistry, validation of processes and regular training.

Standards, safety & hygiene requirements in the medical environment

Ultrasonic cleaning in the medical sector is subject to strict regulatory requirements that ensure the protection of staff and patients.

Procedural basis: The KRINKO/RKI recommendations for the reprocessing of medical devices, which define the reprocessing routes, apply to the practical application.
Devices: BANDELIN devices are classified as Class I medical devices according to MDR and bear the CE and MD labelling accordingly.
Manufacturer standards: The company fulfils the ISO 9001 and ISO 13485 standards, which regulate quality and processes relevant to medical devices.
Chemical preparations: Disinfectants and combination products are authorised as class I and II medical devices, for which clinical studies and external expert opinions are required.
Personnel protection: It is guaranteed by contactless pre-cleaning in the ultrasonic bath and the use of combination preparations. These offer user protection by inactivating contaminated instruments in the bath without replacing thermal disinfection. This significantly reduces the risk of cuts and infections.
Instrument protection: The gentle cavitation principle prevents mechanical brushing.
Documentation: Process performance is checked via validated processes and the systems' digital process documentation. Smart devices automatically log cycles (duration, temperature).

Cost-effectiveness: time savings, process reliability & long instrument service life

Ultrasonic cleaning makes a measurable contribution to process reliability, cost efficiency and sustainability. Ultrasound enables standardised, reproducible processes, which reduces sources of error caused by manual brushing. Time is saved because several sieves or trays can be cleaned at the same time instead of treating individual instruments one after the other. This massively shortens the pre-cleaning time and noticeably increases the availability of the instruments, reducing operating theatre bottlenecks. The TRISON devices for robotic instruments are a particularly clear example of this: Instead of 15 minutes of manual cleaning per instrument, four instruments can be cleaned together in the automated process in just around 15 minutes - while at the same time improving the cleanability of complex lumens.

Longevity and cost reduction

Investing in high-quality, robust devices with a high level of vertical integration in Germany reduces long-term repair and replacement costs. Clinics report that BANDELIN devices have been in reliable use for 20-30 years. Cheaper alternatives often fail early and have to be replaced several times.
As ultrasound does not require any mechanical scrubbing and gentle preparations are used, surfaces, joints and cutting edges are subjected to significantly less stress. As a result, instruments remain sharp and functional for longer.

Future trends: digitalisation, robotics and intelligent ultrasonic cleaning systems

The future of ultrasonic cleaning will be characterised by automation, digitalisation and greater integration into logistics and IT systems.

Automation and digitalisation

Smart systems: The trend is towards touch displays, programmable processes and integrated process documentation (Smart series).
Robotics: In robotic instruments, the trend is clearly moving towards fully automated, validatable systems such as TRISON, which combine cleaning, rinsing and movement to safely reach even complex lumens.
New applications: New fields of application, such as the cleaning of 3D-printed parts, are being added.
Integration: Future systems will be able to be integrated even more closely into digital process landscapes (AEMP IT and logistics).

Sustainability and service

Although sustainability is not yet a primary purchasing criterion, it is increasingly being taken into account. Durable, repairable technology and energy-efficient modes (eco modes) reduce the consumption of resources.g

Conclusion

The ultrasonic cleaner is indispensable in modern medicine. It serves as a necessary pre-cleaning step that uses the cavitation principle to reliably and gently remove dirt from instruments where manual methods fail. Ultrasonic cleaning enables standardised, reproducible processes, increases the occupational safety of personnel and extends the service life of instruments.
As a certified manufacturer of medical devices (Class I), we at BANDELIN combine technical precision with medical experience and manufacture durable, reliable devices - from stand-alone devices in the practice to automated systems for robotic instruments. Consistent compliance with KRINKO/RKI regulations and digital process documentation ensure maximum hygiene safety and cost-effectiveness.

FAQ on the topic of ultrasonic cleaners for medical instruments

Which instruments must not be cleaned in the ultrasonic cleaner?

Optics, flexible endoscopes and electrical instruments where contact with water and electricity would be critical are not suitable. However, ultrasonic cleaning is suitable for almost all surgical instruments made of stainless steel, including MIS and robotic instruments, dental instruments and implant instruments.

Does an ultrasonic cleaner replace disinfection in the washer-disinfector?

No. Ultrasonic cleaning is clearly assigned to pre-cleaning in order to remove residues. Subsequent disinfection must be carried out thermally in the washer-disinfector at around 95 °C, followed by sterilisation.

Which chemicals are suitable for ultrasonic baths?

Pure water is insufficient. Cleaning products (enzymatic or surfactant-based) are required that are customised to the soiling and whose effect is enhanced by ultrasound. Combination products (such as STAMMOPUR) offer additional user protection.

How long does a typical ultrasound cycle take?

According to the manufacturer's instructions, the sonication time must be sufficient to completely remove all residues and depends on the soiling and the cleaning medium. It is crucial that instruments are placed in the bath as soon as possible after use so that blood and tissue do not dry out and the cleaning time is unnecessarily extended.

How often does an ultrasonic cleaner need to be validated or tested?

The effectiveness of the cleaning and disinfection products is verified by external expert reports and authorisation studies. In practice, quality assurance is carried out using validated processes. The test intervals for the devices are based on legal requirements, such as the MPBetreibV.

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Bandelin Electronic

Quality since 1955

We - a Berlin-based family business in its third generation - specialise in the development, manufacture and distribution of ultrasonic devices, corresponding accessories and application-specific cleaning and disinfection preparations. The high vertical range of manufacture, a modern production facility and motivated employees distinguish us and are guarantors for constantly new quality products.