Rising freeze-dried demand drives improvements to control automation

Optimal Industrial Automation, one of the UK’s leading integrators of ‘difficult to deliver’ automation systems for the food, pharma and chemical industries, has developed a range of control automation solutions for pilot and commercial-scale freeze-dryers

ptimal’s solutions champion the use of closed loop control, SCADA layers and the latest data historians to improve system efficiency, plant integration and the quality and consistency of the finished product. Here, the process is broken down into its key stages and consideration given to the various control options available. Martin Gadsby, Optimal MD,


comments: “We are well known for building and integrating automation systems for life science and other process industry manufacturing equipment, typically when the application or surrounding conditions make it too complex to deliver for the majority of mainstream system integrators. “Working with freeze-dryers is no different, however, since Optimal has completed a large number of new and retrofit projects in this area we have used our experience and knowledge to develop and formalise a range of control systems specifically for industrial freeze-dryers. “The result is a flexible service offering, that is also fast to specify and deliver, the ultimate goal obviously being a more reliable process, improved productivity and reduced costs for the end customer or operator.”

UPDATING THE PROCESS “The freeze-drying process was originally developed as a commercial technique that enabled serum to be rendered chemically stable and viable without having to be refrigerated. Since then the process has been developed considerably allowing freeze-dried medicines to be easily reconstituted using purified water for ingestion or injection, but, the principles remain the same: “Freeze-drying in this context is the process by which water (and other solvents) are removed from a frozen material by sublimation and secondary processing. The sequence is generally as follows: freezing, primary drying (sublimation), and then secondary drying (desorption).

“It is essential that these stages are

precisely controlled and independently monitored to achieve a consistent product with an extended shelf-life which is far easier to preserve in a packaged form and is less sensitive to temperature variations, making it easier to transport or feed-in to the next stage of processing.”

CONTROLLING THE PROCESS The high financial value of pharmaceutical products and strict manufacturing and traceability guidelines set largely by the US Food and Drug Administration (FDA) also make it essential that correct procedures are followed and records maintained. There are some major challenges therefore during the process that makes close control particularly important. Any control system used for a freeze-

drying application should ideally be capable of automatically adjusting the process to maintain the ideal conditions. The control system must therefore provide a fast, easy to use HMI and inherent control flexibility, in addition to providing accurate and reliable control of each freeze-drying cycle. Traditionally, open loop control systems have been used, with the freezing and heating temperatures and the chamber pressure being controlled according to a specific profile. However, this approach has several drawbacks, including the inability to cope with temperature variations outside of the set profile. With no way of accelerating the process if conditions change, the overall freeze- drying period is also prolonged. For optimum control of the freeze-

drying process, a closed loop control system should be used. Data from the pressure and temperature sensors is fed back to the controller where it is compared to a reference value. The controller takes the difference between the output and the reference value and uses it to change the inputs to the system to help compensate for the difference.


Demand for aseptic packaging and preservation, as well as the rise in production of protein-based drugs is expected to continue to boost global demand for freeze-drying capacity. This means pharmaceutical

manufacturers and their equipment suppliers are turning to an array of advanced process analytical technologies (PAT) to help optimise their freeze-drying operations

The result is a more dynamic and precise control of the freeze-drying process, with the ability to address any unexpected fluctuations in process conditions.

DATA COLLECTION AND USE IS VITAL The main innovations in the recent development of freeze-dryers have been in process control and the automation of the loading and unloading processes. Optimal has used its in-depth knowledge and experience to develop a range of integrated control systems for freeze- dryers. Ranging from client server SCADA systems to much more basic designs, a system can be developed to suit the exact requirements of the client. Optimal has also achieved significant

improvements in productivity by the use of data historians to capture critical and quality parameters. Data historians allow users to archive and retrieve years of useable data in a fraction of the time of a conventional relational database. Data is formatted and presented in way that is easy to process and interpret. When combined with Overall Equipment Effectiveness (OEE) systems, the performance and productivity of each dryer is maximised. Due to the inherently complex nature of freeze-dryers, the standard offering provides a high level of automation for a single system. The use of a single SCADA interface on the system offers fully automatic as well as manual control. The design has a recipe system together with historic and real-time trending, plus data logging, to allow batch reports to be produced.

Optimal Industrial Automation T: 01454 333222


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