Ultrasonic cleaning in hospital technical services

A hospital is also a large building with a workshop and a kitchen. Castors on trolleys wind up with hair and thread, extract filters over the kitchen ranges load with grease, ventilation grilles and washable filters gather dust, and pumps, valves and fans from building services come apart for repair. None of this is patient-contact equipment, and cleaning it is industrial work for technical services and catering. An ultrasonic tank does it faster and more thoroughly than a sink and a brush, and it reaches axles, bearings, filter mesh and louvres that a brush does not.

The boundary

The line is set by what a part is and where it goes next.

Instruments and devices reprocessed for patient use go to the sterile services department. In the EU, equipment specifically intended for cleaning, disinfecting or sterilising medical devices is itself a medical device under Regulation (EU) 2017/745, Article 2(1). That department uses equipment certified for the purpose, washer-disinfectors to EN ISO 15883, and follows the reprocessing instructions of each device maker (EN ISO 17664). Sonixtek machines are industrial cleaning equipment and are not certified as medical devices.

Some equipment the workshop maintains is itself a medical device: electric hospital beds, patient hoists and wheelchairs, for example. For these, the device maker's service instructions decide which parts may be removed and cleaned and how. A castor taken off such a bed for repair can be a workshop part, but the bed as a whole goes back through the hospital's cleaning and disinfection routine before it returns to a ward.

Ultrasonic cleaning never disinfects. Items coming from wards are handled by the infection prevention team's rules, which usually means surface disinfection before they reach the workshop, and gloves in the workshop.

Castors and trolley parts

Hair and thread wound around an axle are cut and pulled off first; ultrasound loosens what is left but does not unwind a wrapped fibre. What remains, old grease, floor-care residue and dirt, comes off in an alkaline cleaner at 55 to 60 °C, 28 kHz, in 10 to 15 minutes. Castors with sealed bearings can take on water past the seals, so they are dried with hot air and blown out, and relubricated before they go back on. Polyurethane and rubber treads stay within the temperature their maker gives. See removing oil and grease.

Kitchen parts

Extract filters, fryer baskets and gastronorm pans carry polymerised cooking fat, which is sticky and hard to remove by hand. A heavy-duty alkaline cleaner at 60 to 70 °C with 28 kHz takes it off in 15 to 30 minutes, depending on how long the filter has been in service. Parts that touch food are cleaned with food-safe chemistry and rinsed in potable water; see stainless steel food contact parts and food industry filters. Fat loads a bath quickly, so a skimmer or a filtration unit keeps it working for more than a few filters.

Filters and grilles

Washable metal mesh pre-filters from air handling units and supply and extract grilles collect fine dust bound by moisture and grease. A mild alkaline cleaner at 40 to 50 °C and short cycles are enough. Powder-coated grilles are checked on a sample first: a sound coating is not affected, but a coating that already has poor adhesion will lift. Paper, glass-fibre and synthetic filter media are not cleaned; they are replaced. See industrial filters for the principles.

Workshop parts

Pump impellers and casings, valve internals, fan parts and small gearboxes from heating, water and ventilation systems are cleaned as in any maintenance workshop: alkaline cleaner at 55 to 65 °C, 28 kHz for heavy parts, 40 kHz for small and fine parts, then rinse, dry and oil. Seals and gaskets are replaced, not cleaned.

Which machine

A hospital that runs one tank for workshop and kitchen parts keeps the two apart in time and chemistry: food-contact parts never in a bath that has just cleaned oily pump parts. See how to size a tank and the medical industry overview.