Everything you need to know about work safety, ultra-low temperatures, storage and transport

How does the Stirling Ultracold engine work?

Unlike conventional ULT cascade systems, Stirling Ultracold uses a free-piston Stirling engine design. The Stirling engine essentially consists of a piston with helium gas bearing, the displacer and the linear motor. With low electrical power, the linear motor drives the piston back and forth, which compresses and expands the helium. The cold resulting from the expansion is transferred to a gravity-driven thermosiphon containing the coolant ethane (R170). The ethane condenses on the cold Stirling engine and runs down the thermosiphon thanks to gravity, thus cooling the inside of the cabinet. The liquid ethane becomes gaseous again when the heat is removed from the inside of the cabinet. Thus, it rises up the thermosiphon in gaseous form until it condenses again on the cold Stirling engine and the cycle starts once more from the beginning.

The Stirling engine explained in a video

The Stirling engine in use at NASA

Illustration thermosiphon

Cross-section Stirling engine

How can I minimize the liquid nitrogen consumption on my CBS cryogenic storage equipment?

The amount of liquid nitrogen consumed depends on a number of factors. One decisive factor is how often you open the lid and store or remove material. The other decisive factor is the set point you select on the control panel for liquid nitrogen fill level settings. Selecting a low set point of 20 cm and a high set point of 55 cm extends the cycle until the system starts the next filling. This minimizes the amount of liquid nitrogen consumed as, with each filling process, liquid nitrogen is used to cool down the lines and therefore does not reach the storage equipment. Another factor is the quantity of product you store. The greater the amount of mass, the lower the liquid nitrogen evaporation rate. Whenever possible, try to store to full capacity.

How do I switch my CBS cryogenic storage equipment to emergency mode operation?

In the event of a power outage or malfunction, it may be necessary to switch to manual filling. The systems are fitted with a manual fill port located on the back or the right-hand side of the equipment. Follow the step-by-step guide below to perform a manual fill:

1. Shut off the liquid nitrogen feed valve located on the supply tank or the supply line.
2. Disconnect the supply line from the autofill port on the freezer.
3. Remove the cap from the manual fill port and fit it where the hose was removed. Screw the cap in place.
4. Connect the liquid nitrogen supply line to the manual fill port and screw the hose in tight.
5. Open the lid.
6. Open the liquid nitrogen feed valve.
7. V Series models: Fill the hose with liquid nitrogen until you see the liquid nitrogen begin to “sputter” out of the wall openings, then close the feed valve. At this time, you now have around 63 cm of liquid nitrogen in the wall; in other words, a complete fill. eV Series models: Fill with liquid nitrogen until it reaches the base of the platform, then shut the feed valve.
8. Close the lid.
9. Repeat these steps daily or until the autofill function has been restored.

Drawer or side access racks? Which is better for my Stirling ultra-low temperature freezer?

Drawer racks offer the advantage of providing easy access from the front to individual boxes without having to take the whole rack to the heat. In addition, in the Stirling SU780XLE, a drawer system is the only way to increase capacity from 600 to 700 boxes in the standard 2-inch format.

Side access racks offer the advantage of being somewhat lighter and less expensive. Choosing the appropriate system is also often a matter of employee preference.

How do I achieve the best safety results for products stored in my CBS cryogenic storage equipment?

The best safety results in terms of having constantly low temperatures and sufficient response time in the event of a malfunction are achieved by increasing the low set point and high set point. The low set point is especially important. For ultra-low temperatures, we recommend selecting a low set point of 35 cm and a high set point of 55 cm.