How to clean an autoclave: a guide by type of unit
— Equipo JP Selecta
Keeping the chamber and internal components of an autoclave in optimum hygienic condition is a critical factor in ensuring the reproducibility of sterilisations, avoiding failures in cycle validation and preventing breakdowns of pumps or solenoid valves.
A rigorous cleaning protocol adapted to the specifications of each model not only extends the service life of the unit, but also ensures that saturated steam acts without mineral or biological interference.
Cleaning procedure according to the type of autoclave
The design of the chamber and the purging technology determine the critical points where residues accumulate. For this reason, cleaning tasks must differ according to the autoclave model.
Cleaning a vertical autoclave
In top-loading models (such as the Presoclave III Plus or the Autester ST DRY USB-S and GMP-S):
- Access to the gasket and thread: the lid gasket and the upper closing mechanism must be cleaned daily with a clean, damp, lint-free cloth. In screw-closure systems, it is crucial to inspect the screw thread, where solid particles tend to build up and can degrade the seal over time.
- Bottom of the chamber and heating element cover: in vertical autoclaves, gravity causes residues, salts or any spills to accumulate at the bottom of the chamber. The heating element cover grid must be removed periodically to clear any sediment deposited in the lower blind area.
- Cleaning the drain filter: the mesh filter located at the bottom of the chamber must be unscrewed and cleaned (the use of ultrasonic baths is recommended) to prevent dirt particles from clogging the purge line.
Horizontal benchtop autoclave
In front-loading models (such as the Autester ST DRY PV 12, Autester ST DRY PV-B Print or Autester ST DRY-S):
- Door gasket and contact surface: these must be cleaned daily with a clean, damp cloth, with the unit completely cold and without abrasives, steel wool or chloride-containing products. To prevent steam leaks, it is advisable to periodically wipe the gasket seating edge with a soft cloth dampened with distilled water and to check before each load that the gasket is properly seated in its groove.
- Trays, chamber and drain filter: the trays and their holder are removed to clean the chamber, especially the bottom (on the PV-B Print, at least once a week). The unit must be slightly raised at the front so that water collects at the back, in the drain area, where the drain filter is located: if it becomes clogged with grease, dust or dirt from the instruments, vacuum and drying performance suffer.
- Clean and used water tanks: these units have two independent tanks that are emptied separately from the front valves. The used water tank must be emptied frequently (ideally every time the clean water tank is refilled), and the tanks are cleaned and disinfected at the intervals indicated in the manual for each model. The unit must not be moved or tilted with the tank full.
Autoclave with pre-vacuum/post-vacuum
In units fitted with a vacuum pump (Class B):
- Vacuum system filter: the internal drain filter protects the extraction line. A filter clogged with paper or agar residues degrades pump performance, lengthening the pre-vacuum phase or generating pressure error codes (Vacuum Failure).
- Preventive cleaning: it is essential to clean the chamber before introducing loads that may shed particles, preventing the vacuum line from drawing in organic residues.
Autoclave with drying (ST DRY PV technology)
A step unique to these units: cleaning the bacteriological air filter. Autoclaves with a filtered-air drying phase incorporate an air inlet microfilter (0.20 µm porosity).
This filter requires periodic inspection and replacement (quarterly/every six months). A clogged filter prevents the proper intake of sterilised air, reducing drying efficiency and leaving residual moisture in the pouches.
→ You may be interested in: Vertical vs horizontal autoclave.
Points to consider for correct cleaning: water quality
The water used both for steam generation and for rinsing tasks is decisive for the preservation of the boiler, made of AISI 316L stainless steel.
Ordinary mains water contains salts (calcium and magnesium carbonates) that form scale on the heating elements and solenoid valves as it evaporates, reducing heat transfer and causing blockages.
On the other hand, ultra-pure or double-distilled water deionised to extreme levels must not be used, as its high aggressiveness attacks the passivation of the stainless steel itself.
What conductivity should the water have?
It is recommended to use distilled or demineralised water with a conductivity above 100 µS/cm. This conductivity level ensures the correct operation of the boiler's conductivity level sensors without causing corrosion or limescale deposits. In addition, the water must be classed as soft water (≤17 mg/l of CaCO3).
What happens if the autoclave is not cleaned correctly?
Poor cleaning or the use of unauthorised products triggers immediate operational failures:
- Dried-out or scaled gasket: it loses its seal, causing steam leaks. The unit does not reach the set pressure and the cycle is aborted by an alarm.
- Scale on the temperature probes: the build-up of deposits insulates the Pt100 sensors, producing erroneous readings that may validate a cycle that has not physically reached the sterilisation temperature.
- Clogged drain filter: it hinders the evacuation of condensate, lengthening the draining time or causing sterilisation errors due to the presence of cold water at the bottom.
- Dirty water tanks left unemptied: they produce unpleasant odours, biological growth and contamination of the steam generated in subsequent cycles.
How do we know whether we are cleaning an autoclave properly?
| Sign | Probable cause | How do we fix it? |
|---|---|---|
| Persistent odour after the cycle | Organic residue not removed from the chamber or the drain filter | Clean the chamber with a damp cloth and disinfect the mesh filter in an ultrasonic bath |
| Visibly dried-out or cracked gasket | Limescale build-up due to poor water quality or steam residues | Clean the gasket daily with mild soapy water (rinse well). Check the water conductivity |
| Filter clogged with agar/biological residue | Spills of culture media during the depressurisation phase | Dismantle the filter assembly (A and B) and clean it with hot water or ultrasound |
| The cycle does not validate (exception) | Gasket leak due to dirt or loss of seal | Inspect the gasket and its seating groove. If the alert persists, contact the technical service |
J.P. Selecta maintenance and cleaning recommendations
At J.P. Selecta, we set out the following recommended maintenance guidelines in our official manuals:
- Cleaning products: use only soft, lint-free cloths and neutral, biodegradable, non-aggressive detergents (such as J.P. Selecta's special phosphate-free Bio-Sel detergent). The use of metal scourers, steel wool or cleaners containing chlorides or bleach is strictly prohibited, as they destroy the protective layer of the stainless steel.
- Automatic cleaning programme: for models with a PLC, it is recommended to run the specific Cleaning Programme monthly (or weekly after intensive use) (134 °C for 20 minutes with the boiler empty and clean water) to remove deposits in the internal pipework.
- Replacement of consumables: it is advisable to change the silicone door gasket every 1-2 years depending on the workload and to replace the bacteriological air filter periodically to maintain maximum drying efficiency. To order original spare parts or schedule the mandatory annual service, you can consult our official technical services.