We have been supplying, maintaining and calibrating autoclaves for over 20 years, so when you buy an autoclave from us you can be assured of our expertise in every step.
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We have compiled this useful guide of what to consider when buying an autoclave and you can also call us on 01278 788283 or email enquiries@boostlabcare.co.uk for more information.
Circular chamber against rectangular chamber
Front loading autoclaves with circular chambers have less useful chamber space than a rectangular chamber. However a top loading circular chamber autoclave has a better use of chamber space by using round baskets. Due to the irregular pressure dynamics of a rectangular chamber strengthening struts have to be fitted to the chamber, which has the knock on effect of being more expensive to manufacturer. In brief, circular chamber autoclaves are less expensive than rectangular chamber autoclaves.
Separate steam generator against water weir within the chamber
The big advantage of a separate steam generator is that the steam is injected into the chamber, allowing full use of the chamber space. Secondly, the load reaches sterilising temperature quicker once the generator is producing steam and equally the load cools quicker because there is not a mass of water to cool down. The downside with separate steam generators is there is more to maintain - pumps, valves etc. so servicing will be more expensive. A weir autoclave uses a small amount of the chamber space to hold the water and heaters. They take longer to cool due to the thermal mass of the water but are easier and cheaper to maintain. Weir autoclaves are less expensive than autoclaves with separate steam generators.
Air cooled against water cooled
Both systems of cooling are equally as effective, however an air cooled autoclave blows ambient air over the chamber, which has the effect of increasing the ambient temperature. This can make the room the autoclave is located uncomfortable to work in. A water cooled autoclave utilises either a water jacket around the chamber or a cooling coil within the chamber or both. This has the advantage of taking the heat down the drain and not heating the room. Water cooling is also easy to control by the use of adjustable valves. The downside is increased water usage and added maintenance costs.
Load sensed autoclaves
Not all autoclaves are load sensed, which means the sterilising timer does not begin counting down until the load has reached the set sterilisation temperature. This is achieved by use of a load probe placed within a dummy load, similar to the load being sterilised. An autoclave that just senses the chamber temperature starts the sterilisation timer when the chamber reaches the set sterilisation temperature, however the load may not have reached the desired sterilisation temperature by the time the chamber has. This means an estimate, or validation cycles, have to be conducted to determine what time should be set on the sterilisation timer. For example, if a load comprising of bottles containing media requires sterilisation at 121°C for 15 minutes, the settings on a load sensed autoclave would be a set temperature of 121°C and the timer set for 15 minutes. Using an autoclave with no load sensing, the set parameters could be 121°C and the timer set for 26 minutes. It should be noted that the time set might change if using a load with different size bottles.
Services required for a successful installation
Before an autoclave can be installed it is essential that the correct services are available. There are generally three services required, electrical supply, water supply and a drain. Sometimes there maybe a requirement for a compressed air supply and a steam supply (if the autoclave is a direct steam model) The electrical supply is normally a three phase supply unless the autoclave is a very small model. It should be able to deliver the power required by the autoclave usually measured in kW. For example the autoclave may have a total power rating of 9kW (3kW per phase). The power outlet should be mounted on the wall as close to the autoclave as possible but with clear easy access to facilitate easy isolation. The water supply should come from a header tank mounted high enough to supply water at the flow rate required by the autoclave. The autoclave must not be connected direct to the mains water supply to ensure no contamination can occur. The water supply should have a shut off valve to isolate the water supply during servicing. The drain should be capable of accepting a flow of water and be able to withstand direct steam. If this is not possible a condenser unit can be fitted to the autoclave to condense out the steam and reduce the water temperature. This will increase water usage. The drain should be mounted lower than the drain output of the autoclave, preferably in the floor. The autoclave specification should list everything that is required from the services to ensure correct installation. If you are in any doubt ask the manufacturer or the distributor.
Validation against calibration
When an autoclave is installed it is often necessary to ensure that the gauges, displays and chart recorders are reading correctly. This can be achieved by calibration, comparing the results from the gauges and displays against a known standard. However this only proves that the gauges and displays are reading correctly - it does not ensure the autoclave is functioning correctly or that the load placed within the autoclave is reaching the desired temperature for the desired time (or going above the required temperature for longer than required). To prove these requirements a number of validation cycles are conducted but before this is conducted the autoclave is calibrated. A decision should be made to what common loads will be placed in the autoclave, what the set parameters should be set and what the required acceptance criteria should be (e.g. 121°C for 15 minutes +/- 2°C +/- 1 minute) Then a number of thermocouples, usually 12, will be placed within the chamber and load, the autoclave cycle is started and the thermocouples are monitored to ensure the load and chamber are reaching the correct temperature for the correct time.
IQOQPQ
IQOQPQ (Installation qualification, Operational qualification and Performance qualification) is sometimes requested by the customer to ensure that they will get the optimum performance from their autoclave. This involves ensuring the autoclave is installed correctly to the correct services and documenting the process. Secondly, the autoclave is operating correctly (meeting the specification of the autoclave) and that the autoclave is correctly operated by the users (this should involve training of staff). Finally the performance of the autoclave is checked (validation) to ensure the autoclave meets the customer’s specific requirements. The whole process is documented and makes up the IQOQPQ document. It is good practice to begin compiling the IQOQPQ document before the autoclave is purchased to ensure the correct autoclave is purchased.
What is the next step?
We are here to help and advise so please do not hesitate to contact us:
Telephone: 01278 788283
Fax: 01934 310460
Email: enquiries@boostlabcare.co.uk
