ANALYTICAL AND LABORATORY EQUIPMENT 27
100°C so that the liquid load temperature can catch up with it. In some systems there is the option to pulse the ‘freesteaming’ by repeatedly allowing pressure to build and then releasing it to assist with air removal from laboratory waste loads, in particular. Freesteaming of pulsed steaming is not suitable for liquid loads however. For more stubborn loads that contain a number of air pockets, such as wrapped instruments or fabrics, especially where large or tightly packed loads are concerned, air removal can be further assisted by using a vacuum system at the start of a cycle to remove air from within the autoclave chamber and load, which can then be replaced actively with steam as the autoclave heats up.
A false economy Having established what is required within the chamber environment (dry saturated steam), it is important to appreciate that care is required
when loading. Sterilisation can only take place if the steam is allowed to flow freely within the chamber so that it comes into direct contact with items to be sterilised – waste, glass bottles, etc. Laboratories looking to invest
in a new autoclave and requiring a higher throughput may initially look to purchase a rectangular chamber design. Size for size in chamber capacity, it would seem to offer better loading than that of a cylindrical machine and
look to be the right choice; more items could be crammed into the chamber. Is it a better buy? Is it false economy? What are the pros and cons? Te table below shows just four basic comparisons. Te comparison will hopefully encourage autoclave purchasers to raise more issues such as cycle times for heating and cooling, and become aware of the important of load density. It could sway the buying decision
Rectangular chamber autoclave
More expensive, could be up to 50% more costly.
More metal, greater density – longer to heat up.
Uses more energy.
Extended heating time reduces number of sterilising cycles per day.
Potential for easily overloading the chamber.
with regard to what solution can process more. In actual fact, a cylindrical chamber autoclave often offers a lower cost of ownership and is more energy efficient.
For more information ✔ at
www.scientistlive.com/eurolab
Tony Collins is MD of Priorclave.
www.priorclave.co.uk
Cylindrical chamber autoclave
Less expensive, simpler manufacturing process, quicker customer delivery.
Less metal, heats up more quickly.
More efficient, lower energy costs. Faster heat-up means more sterilising cycles per day.
Cylindrical chambers by their nature tend to prevent overloading.
Consideration should be given as to how efficient a rectangular chamber design is when fully loaded
www.scientistlive.com
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