Abstract: Freeze drying apparatus and associated lyophilization procedures are provided employing vapor flow detection and/or vacuum control for monitoring and control of the lyophilization process. The vapor flow detector, such as a windmill sensor, is disposed to monitor vapor flow from product undergoing lyophilization. In a batch process, vapor flow is collectively monitored with the vapor flow detector between the process chamber and condenser chamber, while in a manifold configuration separate vapor flow detectors are employed at each flask attachment port. A windmill sensor provides visual feedback to an operator and/or electronic feedback to a system controller. A vacuum control system is also provided for use with or independent of vapor flow detection. This vacuum control disconnects the vacuum source from the process chamber when pressure within the process chamber falls below a first predefined set point.

Abstract: Freeze drying apparatus and associated lyophilization procedures are provided employing vapor flow detection and/or vacuum control for monitoring and control of the lyophilization process. The vapor flow detector, such as a windmill sensor, is disposed to monitor vapor flow from product undergoing lyophilization. In a batch process, vapor flow is collectively monitored with the vapor flow detector between the process chamber and condenser chamber, while in a manifold configuration separate vapor flow detectors are employed at each flask attachment port. A windmill sensor provides visual feedback to an operator and/or electronic feedback to a system controller. A vacuum control system is also provided for use with or independent of vapor flow detection. This vacuum control disconnects the vacuum source from the process chamber when pressure within the process chamber falls below a first predefined set point.

Abstract: The circulation of heat transfer fluid through the low temperature heat exchanger in the temperature control system of a freeze dryer is selectively increased when the temperature of heat being applied to the product shelf assembly in the freeze dryer exceeds the desired temperature. Preferably, a servo-controlled mixing valve selectively bypasses the low temperature heat exchanger so that the rate of cooling is very precisely adjusted without requiring the heat exchanger refrigeration unit to be cycled on and off. Since the refrigeration unit operates continuously, the reliability and operating lifetime of the refrigeration unit is increased. Moreover, the heat exchanger temperature is maintained at a minimum value. Preferably, the servo-control for the mixing valve includes a digitally controlled stepping motor and the adjustment of the mixing valve is sensed by a linear voltage displacement transducer. To prevent short cycling and oscillation, a dead band is introduced in the servo-control loop.