The most important consideration when choosing a freeze dryer is to ensure the system is fit for both today's applications and future needs. For the sake of this discussion, we will focus on freeze dryers with fluidfilled shelves, which does not include lowend manifold or heatonly shelf freeze dryers.

An understanding of the available features of a freeze dryer can facilitate the choice. The following are some considerations:

shelf size (m2 )

shelf style (bulk or stoppering)

condensing rate (L/h)

condensing capacity (L)

condenser location (internal versus external)

material (304 versus 316SS)

21 CFR Part 11 compliance.

The freeze dryer manufacturer will also want to know what space is available for the freeze dryer and what utilities, such as electrical, air, chilled water and air conditioning, are available.

The following are a few examples of some of the various options:

Cylindrical or rectangular product chambers — a cylindrical product chamber is less expensive than a rectangular chamber; however, it may occupy more floor space depending on the configuration of the shelf assembly.

Internal or external condenser — an internal condenser is cheaper and provides unrestricted vapour flow. An external condenser is supplied with an isolation valve to separate the product from the condenser, which protects the product from reconstitution during power loss, and keeps the condensate out of the clean room environment.

Pirani or capacitance manometer — piranis, the least expensive vacuum measurement device, read the relative vacuum inside a freeze dryer because they are affected by vapour. The more vapour present, the higher the pressure reading. A capacitance manometer reads the absolute vacuum level and the reading is unaffected by vapour pressure. Most production systems use a capacitance manometer for measurement and control of vacuum level. The best method for determining the 'end of primary drying' is to compare a pirani reading to a capacitance manometer reading. When they read the same, there is no vapour present and the product is dry. A quick test can be conducted by lowering the vacuum level to see if the pirani reading tracks the capacitance manometer. If water is present, the capacitance manometer will drop faster. If no water is present, they will drop at the same rate.

Proportional vacuum control — the least expensive vacuum control system bleeds gas into the chamber using a solenoid valve, providing ±10 mT stability at 100 mT. For better stability, a proportional vacuum controller can be used that regulates the gas bleed through a proportional valve. The result is ±0.5 mT or better control. GuanFeng is your specialist in drying techniques and all your partner for Freeze Dry Machine . The great variety of drying processes enables Guanfeng to always give good and honest customized advice and help you decide which machine best matches your requirements.Please contact us or check below link: if you have any question.