Shell freezer offers efficiency and convenience
Shell freezer offers efficiency and convenience
February 8, 2005
The VirTis benchtop shell bath is a self-contained, compact freezing unit designed for the preparation of flask samples for efficient freeze drying.
It offers a simple and safe method for unattended prefreezing of multiple flasks.
Mounted in a streamlined, compact cabinet, it allows capacities of up to two each 1200ml flasks and up to four each 40ml flasks at one time.
Freeze-drying flasks are automatically rotated by speed controlled, motor driven rollers in a refrigerated bath containing alcohol or any other freeze resistant fluid.
The stainless steel rollers rotate freeze-drying flasks in the -70C bath, evenly distributing a thin coating of liquid product around the inside shell of the flask until it is frozen solid.
To produce the most efficient format, a cylindrical shell, the flask is filled approximately 1/3 full and placed on its side for rotation.
This provides a high surface to volume ratio of frozen sample to be freeze-dried.
A flask lift device permits flasks to be 1/2 filled to form a conical coating.
By elevating the cap end as the flasks rotate, fouling of the lid, filter, and stoppering plug is prevented.
Using this method makes the freeze-drying process far more efficient than other conditions, such as stub-freezing, by facilitating vapour flow from the sample during lyophilization, says Biopharma.
The freeze dry cycle is shortened because moisture does not have to migrate through the ice interface and a thick layer of already dried product while the higher surface area allows better heat transfer.
These refrigerated units are said to provide a simple and safer method of pre-freezing multiple flasks at one time.
Microprocessor-controlled for separate refrigeration, rotation and timer control, the VirTis benchtop shell bath is described as the perfect processing companion to the VirTis benchtop freeze dryer.
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