Choosing a modern autoclave to suit your laboratory needs

For years the laboratory autoclave has been an essential item for microbiological work. However, justifiable but suffocating regulation over the past 30 years has changed the procedure for specification, installation and use.
This has made acquisition more difficult by eliminating the old pick, plug and play procedure. Remember the bucket behind to catch the drips, setting it to 15 minutes at 121¢ªC then emptying it once there was no pressure inside.
The addition of safety systems such as thermal or cooling locks and the increased requirement to ensure the load is sterilised to tougher Laboratory Quality standards has extended cycle times dramatically.

Interfaced control

Now, performance optimisation considers vacuum air removal, venting systems and accelerated cooling options, all accurately interfacing through sophisticated microprocessor control technology.
Performance enhancing vacuum and free-steaming systems and increasing concern about the hazards of exhaust steam from autoclaves, have all led to the introduction of standards and regulations requiring most of them to be connected to sealed and vented drains.
Microprocessor control systems can be a nightmare to technophobes and need to be as user friendly as possible without compromising safety and efficiency.
When sourcing expensive and sophisticated equipment it is essential to ask the right questions, get the right answers and to understand the real purpose of the autoclave, being sure the autoclave has the right specification to perform effectively and efficiently, especially if ultimate proof to a certifying body is procedural.

Questions and parameters

There are many questions and parameters to consider and fulfil among which are:
• What type of autoclave is most suitable? Top or front loading? A top loader has a smaller ‘footprint’ and accommodates taller items but loading/unloading can be more difficult. A front loader is easier to load, has better steam circulation and more difficult to overfill but has less useable space for a given volume.
• Electrically or steam heated? Electrical heated by a separate steam generator inside the autoclave body has fast heat up/cooling times but is more complex and so difficult to fit and maintain. If heated by heaters inside the chamber the system is easy to maintain and service but cooling will be slower unless the water charge can be emptied. Steam heating has the fastest heat up/cooling times but a reliable supply of dry steam is required. There will be additional costs for installing steam reducing and condensate return sets. Condition and possible chemical contamination of the steam should also be considered with autoclave loads that are for re-use.
• Cylindrical or rectangular chamber? As the pressure inside will naturally try to make the chamber round, cylindrical chambers can have thinner walls, making them lighter and less costly. They have better steam circulation and are more difficult to overfill although have less useable space for a given volume. For a given footprint there is more capacity with less wasted space with a rectangular chamber but it is easier to overfill and more expensive to manufacture.
• Manual or power door? Manual Doors are less complex. They require less servicing, are less expensive but the trade-off is the space required for opening and they are more difficult to open than the push-button alternative. Power doors, with vertical or horizontal opening, have a simple push button operation with no ‘door swing’ but still need space for door at rest to the side or underneath the chamber. Many types rely on moving door seals, which can require frequent changing and the complexity of a power door makes them more expensive, requiring regular maintenance.

Further questions

Beyond these hurdles there remain further questions to be considered:
•  What will be sterilised; bottled liquids, glassware, laboratory equipment, porous loads, waste?
•  How much space is required?
•  What services are required?
•  How will the cycle be controlled?
•  How do you prove sterilisation?
Any reputable supplier will be able to provide assistance, advice and information on these questions. Often you will be able to arrange a site survey to make sure that everything is going to fit.
Finally, on-going maintenance and service should be considered as part of the purchasing process. Establish whether preventative maintenance is available and what is covered by different suppliers’ preventative maintenance packages and warranties.
At the end of the day it’s the end user’s choice. Of course price is an important factor but sound research and reliable backup to ensure trouble free installation and operation may very soon turn out to be a wise investment. 

Tony Collins is Managing Director, Priorclave Ltd, Woolwich, London.UK. www.priorclave.co.uk

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