Q:What is a dewar?
A: A dewar is a double walled vacuum jacketed container, used to keep cryogenic liquids well insulated, preventing them from boiling to a gaseous state. The term can get confusing because technically any vacuum insulated container can be called a dewar, from small open mouth flasks, to large pressurized cylinders.
Q: What terms can I use to differentiate the dewars out there?
A: The best way to differentiate between dewars are by their function. An enclosed dewar whose purpose is to store and dispense liquefied gases (LN2, LOX, LH2, etc.) at pressure, would be a pressurized LN2 cylinder. A smaller open mouth flask meant for storing or transfering liquid nitrogen at atmospheric pressure, would be an open mouth LN2 dewar. A dewar that hold biological samples at cryogenic temperatures, would be a sample storage dewar, or a sample storage freezer for a larger automated unit.
Examples of each variety of dewar:
Sample Storage Dewars
- SC Series
- XC Series
- Cryosystem Series
Sample Storage Freezers
- HEco Series
- Stock Series
- MVE Series
Pressurized Liquid Cylinders
- Dura-Cyl Series
- Perma-Cyl Series
Q: How can I transfer liquid nitrogen from a pressurized liquid cylinder to another container?
A: First, you should only attempt to extract liquid from a low pressure (22 psi) liquid cylinder. Higher pressure cylinders are usually reserved for gas use. Next, you must use a cryogenic rated transfer hose. A standard hose has no insulation and will get very cold during use. A vacuum jacketed hose has great insulation and will only get cold at the end fittings, also preserving as much LN2 as possible during transfer. Both hoses are made from 304 or 316 SS. Last, the final connection is either direct to a freezer via its flare fitting, or a phase separator can be added to the end of the hose for easier open dewar filling.
See Hoses, Phase Separators
Q: Does any equipment come with liquid nitrogen?
A: No, all liquid nitrogen must be sourced locally, as transporting LN2 is highly regulated.
Q: Where can I buy liquid nitrogen for our equipment?
A: Liquefied gasses such as liquid nitrogen, argon, helium, oxygen, and others can be purchased from local welding supply shops, or by national molecule distributors such as Airgas or Praxair. Depending on your area, Princeton CryoTech may have a local recommendation.
Q: Does an NER Certiicate (PN 20582341) come standard with Vapor Shippers?
A: The NER Certificate is only available at the time the Vapor Shipper order is placed. Unfortunately, it cannot be ordered after the Vaport Shippers have been built and shipped. The document is serial number specific and will have to be requested at the time the order is entered. Contact Sales@PrincetonCryo.com or 800.232.2796 xt 101 for pricing and more information