When Temperature mapping required for Tray & vacuum tray driers?

Dear Experts,

Kindly clarify my doubts.

When temperature mapping to be done for Tart drier and Vacuum Tray drier?
Is there any frequency?
How long temperature mapping to be done?
How can select the temperature probes places in drier?
Is it required in Operational Qualification or Performance qualification?

Please supply your valuable feed back.

Thanking you

Pulla Reddy Karnati.

Your starting point is to determine what your operational parameters are for the dryer? What is longest duration required for drying, what are lowest and highest temperatures required for drying, is drying under vacuum or without vacuum etc.

Temperature mapping typically should cover worst case so if the ovens dry product for 24 hours then you should temperature map at each temperature for 24 hours. You should temperature map at at least 3 temperatures - bracketing the lowest and highest operational temperatures and an intermediate temperature e.g. 30, 50 and 100degC.

Calibrated temperature probes should be used and the probe tip should be taped directly to the tray surface to record temperature of the tray if material is dried directly in the tray. Probes (PT100 thermocouple probes or equivalent) should be calibrated to cover the required test temperatures and there should be a sufficient number of probes to cover the geometric area of each tray (front, middle,back etc.) to ensure material homogeneity under drying conditions. If possible try to use thermocouple probes and a logger that can be placed entirely in the oven as running cables through the door seal may impact your results (some tray dryers will have a port available for running cables). If operationally you dry under vacuum then you should temp map under vacuum.

Frequency of remapping will be a risk-assessment - do your ovens have an alarmed monitoring system attached recording real-time data from calibrated temperature indicators or do you rely entirely on a calibrated temperature gauge and temperature mapping data? I personally would perform annually unless you can justify otherwise - can you afford the customer confidence and financial impact of a failed batch due to an oven running a higher temperature than displayed?

Hope this helped.