Lyophilisation is a complex process of removing water from the product through sublimation at low temperature & vacuum. The equipment (often called freeze dryers) is a very difficult type of chamber to thermally map. A freeze dryer has many shelves that are closely spaced together to hold product. Accurately measuring the shelf temperature during the process cycle can be quite challenging particularly if using thermocouples.
Installation of thermocouples into a freeze dryer is very time intensive. Thermocouples must be threaded into the chamber through the vacuum line using a special flange assembly (see Accessories). The tip of each thermocouple must be carefully “strapped’ or taped onto multiple positions of each shelf. If not done properly, the shelf temperature measurements will not be accurately mapped. Vacuum leaks and broken thermocouples are common problems which can add significantly to equipment downtime.
Using a thermocouple based system (i.e. XpertVal System) for this application should be considered only if seeing “live data” is absolutely necessary. For example, the freeze dryer is new and has never been qualified. In this case, seeing “live data” may be advantageous to allow for mechanical adjustments or to determine product load configurations.
The better alternative is to use wireless dataloggers that are designed to handle this application. The Lives XpertLog System of wireless dataloggers are ideally suited for mapping freeze dryers. Each datalogger has an 18 inch extended RTD sensor. A copper cap is provided that slips onto the bottom portion of each datalogger. The copper cap has a groove so that the RTD sensor can be flush mounted. The datalogger can then be placed on any shelf location with the RTD thermally insulated to the shelf temperature. (See picture above).
In summary, the Lives XpertLog System of wireless dataloggers can save substantial hours of labour and equipment downtime for this application – see chart. Also, periodic verifications of the process conditions can be easily done without disruption to operations.