Laboratory equipment Lecture (9)

TYPES OF AUTOCLAVES DOWNWARD DISPLACEMENT AUTOCLAVES Air is removed in two stages and sterilization is effected by an atmosphere of pure steam. The minimum exposure time is required for sterilizing instruments is 50 minutes at 131ºC or 60 minutes at 136ºC. Bulky dressings, surgical swabs and surgical drapes require exposures two or three times as long.

HIGH VACCUM / HIGH PRESSURE AUTOCLAVE Air is removed by powerful pump. Steam penetrate the load instantaneously and very rapid sterilization of dressings, instruments, lap sponges and packs is possible in 15 to 30 minutes at 134ºC.

THE STEAM STERILIZATION PROCESS WHICH IS DIVIDED IN TO FIVE DISTINCT PHASES: PHASE I The loading phase - in which the objects or items are packaged and loaded in the sterilizer.

PHASE II The heating phase – in which the steam is brought to the proper temperature and allowed to penetrate around and through the objects in the chamber.

PHASE III The destroying phase – or the time-temperature cycle, in which all microbial life is exposed to the killing effect of the steam. PHASE IV The drying and cooling phase – in which the objects are dried and cooled, filtered air is introduced into the chamber, the door is opened and the objects are removed and stored.

PHASE V Testing phase - in which the efficiency of the sterilization process is checked. All mechanical parts of sterilizers, including gauges, steam lines and drains, should be periodically checked by a competent engineer.

Working of autoclave Steam enters the chamber jacket, passes through an operating valve Enters the rear of the chamber behind a baffle plate

It flows forward and down ward through the chamber and load, existing at the front bottom. Pressure regulator maintains pressure in the chamber and jacket at a minimum of 15psi, the pressure required for steam reaches 121°C

Some causes of failure to produce a sterile load are: Faults in the autoclave and the way it is operated It maybe: Poor quality steam Failure to remove air and condensate Faulty gauges and timings Leaking door seals

Errors in loading Examples: Large packs Excessive layers of wrapping materials Over packing

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