Freeze Dryers

How Do Freeze Dryers Work?

Food or other materials are placed in a vacuum tight chamber which is cooled to between -30 °F to -50 °F (-34 °C to -46 °C), below the triple point of the liquids you’re trying to remove (usually the primary liquid you’re trying to remove is water). The material is given time to freeze, then a vacuum pump creates a vacuum (reduces the pressure) in the chamber, effectively reducing the temperature where liquids or solids will transition into a gas. Once the material is frozen, the chamber is gradually warmed (still under vacuum), which turns the frozen liquid into a vapor or gas through sublimation (when a solid turns directly into a gas, skipping the liquid stage, hence the importance of the triple point). The triple point for water is 0.01 °C and 4.58 Torr.

The process removes all liquid from the material, then the chamber is returned to atmospheric pressure by reintroduction of a dry gas like nitrogen. The material must then be packaged inappropriately sealed packaging to prevent the reintroduction of any liquids. Throughout this whole process, the physical form of the material is kept intact, and the residual moisture still left in the material is usually in the range of 1% to 5%.

Vacuum Gauges for Freeze Dryers

Most freeze dryers operate in rough vacuum (10-3 Torr up to 760 Torr or atmosphere) due to the triple point pressure of water at 4.58 Torr, so any of our rough vacuum gauges are an excellent fit for freeze drying applications. For a standalone active gauge, check out the MX2A thermocouple or MX4A convection active gauges. If you’d prefer a rack mountable controller, check out the MV2A controller and the 2A passive thermocouple vacuum gauge. Not sure which product to choose? Chat with us using the window on the bottom right of this screen, give us a call at +1 215 947 2500, or email us at [email protected]!


thermocouple vacuum gauge pirani, MX2A, Televac The Fredericks Company, 215 947 2500

MX2A Thermocouple Active Gauge

• 1*10-4 Torr to 1000 Torr
• Sensors easy to replace
• Excellent resolution and repeatability

convection vacuum gauge pirani, MX4A, Televac The Fredericks Company, 215 947 2500

MX4A Convection Active Gauge

• 1*10-4 Torr  to 1000 Torr
• Senors easy to replace
• Excellent resolution and repeatability

Televac Fredericks vacuum control unit vacuum controller vacuum pressure controller

MV2A Thermocouple

• 1*10-3 Torr to 20 Torr
• Two process relays
• Analog 0 V to 5 V DC output

Televac thermocouple vacuum gauge vacuum transducer vacuum pressure gauge

2A Thermocouple

• 1*10-3 Torr to 20 Torr
• Compact, robust design
• Excellent resolution and repeatability