Positioning of the thermocouples in any temperature mapping exercise is down to judgment. A judgment that must be documented and justified.
In the case of an autoclave, heat is added in the form of pressurized wet steam, anything that can affect the distribution of the incoming steam, can affect uniformity of temperature. Conversely anything that can take heat away from the chamber can affect temperature uniformity.
Lets me say in this VALIDATION ONLINE BLOG, this stage if you want to be pedantic and put tc’s down the drain, the mapping exercise will probable fail. However you are there to verify that product will be sterilized, and product is never placed in the drain. Only the designated product containment area has to be verified.
If this is new installation then get hold of the FAT. In the FAT the chamber is subjected to detailed temperature transfer studies.
Even distribution of the in coming steam can be verified by placing a thermocouple sensor (tc) in each corner of the autoclave (8 tc’s).
Cooling due to heat loss will be maximum the further away you are from the steam inlet and the closer you are to metal that will conduct heat out of the chamber. That is usually, the door, or doors if double sided. If not double sided, then the end wall, and last but not least, the drain. The drain is a big source of heat loss. A tc should be placed as close to the drain, as product would be when the autoclave is in normal use. This gives us an additional 3 tc’s, bringing the total for a standard sized autoclave to 11 tc’s.
I have always considered this sufficient for 1.5 to 2.5 m3 autoclaves. Any bigger and I would concentrate on heat loses i.e. add tc’s to the top and bottom of the doors and or end wall.
It is most important to understand that it is impossible to validate an autoclave while using none validated steam.Your steam must be validated for – superheat – dryness – none condensable gases.
Make certain you do a pre and post mapping calibration, using instrumentation traceable to national standards.Happy mapping.
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4 comments:
I always waiting for your post please update it thanx Autoclaves Products Suppliers
That post is not correct. As a standard you have to have a tc at the reference measurement point ie the coldest part of the autoclave ie the drain. It is the basis of all calculations.
That post is not correct. As a standard you have to have a tc at the reference measurement point ie the coldest part of the autoclave ie the drain. It is the basis of all calculations.
Temperature mapping is the process of mapping the frequency of temperature fluctuations, differences and the range of temperature within a controlled space, over a period of time.
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