Determination of temperature uniformity in freeze-drier compartments.

When referring to freeze drying technology in the pharmaceutical industry, people are concerned about how to produce products with good consistency based on key quality requirements, which requires ensuring the consistency of the production process. The general practice is to conduct process validation (PQ) of the freeze drying process of the freeze dryer. Before conducting specific product PQ, it is necessary to confirm the performance of the lyophilizer in the factory. Once installed in place, as part of the commissioning, it is also necessary to conduct operational verification (OQ) again. The validation should ensure that key process parameters operate within the allowable error range as specified. In a freeze dryer, in addition to the independent and controllable variables that pass the inspection, parameters such as the inlet temperature of the separator, chamber pressure, and time should also be detected. These parameters can help evaluate some variables that directly affect product consistency. One important measurement method is the uniformity of the separator temperature, sometimes referred to as the temperature distribution of the separator.
The temperature of the separator is generally controlled and monitored by a resistance temperature sensor (RTD) well. The separator temperature is commonly referred to as the separator inlet temperature (separator inlet). Heat is transferred from the freeze-drier to the product, and it occurs from the surface of the separator to the interface of the vial. Measuring the actual temperature on the surface of the separator is the key to evaluating the performance of the freeze-drier. The temperature distribution of the separator measured by this method should be compared with the relevant control points and ensure an acceptable range and consistency at the inlet of the separator.
One of the major challenges faced in this type of verification is the ability to measure the actual barrier surface temperature independently of the environment. Temperature measurement equipment can be divided into two categories, direct measurement and indirect measurement. Direct measurement uses fixed temperature sensors, usually thermocouples, to directly measure the surface of the separator. However, the disadvantage of direct measurement methods is that temperature sensors are difficult to fix, difficult to maintain in the low or high temperature range, and often require extensive cleaning of residual adhesives or adhesives. The main advantage of this method is that when operated correctly, it can measure the actual surface temperature at a specific location. Indirect measurement is the embedding of a temperature sensor into a thermally conductive material placed on the surface of the plate layer.
Some devices use indirect measurement principles. The main disadvantage of this type of equipment is that the measured temperature is more susceptible to the environmental impact of the chamber. However, these impacts can be addressed by testing methods. The main advantage of indirect measurement is that it can securely place the device and eliminate any potential residues.
measuring method
The study was conducted at the Lyophilization Technology Corporation (LTI) to assess the temperature uniformity of the laminate based on the ease of use and the effectiveness of many different temperature measuring devices. The research object is a 2 ft 2 single partition lyophilizer and a 24 ft 24 partition lyophilizer. Although other methods have also been studied, only feasible methods are discussed here, including direct measurement with thermocouples (thermocouple devices), indirect measurement with aluminum and copper blocks, and Kaye: ValProbe (ValProbe) (P/N X2534).
Thermocouple devices are often considered the "gold standard" in the temperature distribution of the divider plate, as this measurement involves directly attaching the sensor to the divider plate. The method used here is to attach thermocouples to the plate layer, place the thermocouples at the intersection of two intersecting 4-inch duct tapes, and attach heat conduction to a 1 × 1 inch cooling center belt. There is also the use of plastic tubes with springs to secure thermocouples. In summary, thermocouples are very difficult to fix, especially on the back of the lyophilizer. The LTI lyophilizer used for research has only a depth of 3 feet, making it more difficult to use this method on commercial lyophilizers.

The above content is organized by Superb heater Company, super heater. Mainly professional production: industrial heating elements, temperature measuring elements, production equipment, accessories, and raw materials such as tubular heaters, tubular heaters, belt heaters, ceramic heaters, silicone rubber heaters, thermocouples, etc.

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