Liquid Air and Cryogenic Equipment
How Dewars Fail
Vacuum Jacketed Cryogenic Tank Switcher
Over 20 Years of Growth
Liquid Air Hazards
Liquid Air can be a fire or explosion hazard. Under the right conditions ordinary air can liquefy creating liquid air. Ordinary air near ground level is composed of Nitrogen (78% by volume), Oxygen (20%), Argon (.9%), and a variety of other trace gases. Liquid nitrogen flowing thru an un-insulated pipe creates an outer surface that is extremely cold. So cold, in fact, that surrounding air can liquefy and drip from the pipe. Although not as dangerous as pure liquid oxygen, this oxygen-rich liquid does create a risk of flammability and explosion.
The use of vacuum jacketed transfer hoses
keeps the surface temperature of the pipe near ambient. This prevents the liquefaction of the surrounding air. It also reduces icing that might occur from water vapor freezing on the pipe. Vacuum jacketed pipe is a cleaner and safer option for the transfer of liquid cryogens.
If you’d like to read about liquid air, check out the liquid air article
in the Cryogenic Resource Library
Cryogenic Dewars: Construction & How To Test
Occasionally people will ask what goes wrong with cryogenic dewars or how to tell if a dewar has been damaged from a drop. Dewars are generally quite durable. Lab dewars are typically made of aluminum with a fiberglass neck to reduce heat conduction between the inner and outer surfaces. Most of the insulation occurs from the vacuum between the surfaces. MLI wrap, the same material used to wrap spacecraft, also helps reduce thermal radiation between the surfaces. Some dewars are supported from the neck tube only, but as they get larger usually a trunion is added at the bottom for additional support.
Dewars usually fail because the vacuum has been lost. Perhaps the most common way this happens is when a cryogenic liquid contacts the evacuation port. An evacuation port is used to create the high order vacuum between the inner and outer vessels. This port is then sealed with an o-ring plug. When the o-rings are frozen by liquid nitrogen, the vacuum can be lost.
A dewar that has been dropped, especially if full, can also get damaged if the necktube cracks or breaks from the impact. Provided the vacuum is still intact after dropping a dewar, chances are it will still work fine. A high quality dewar
will give you many years of service and rarely lose vacuum.
One way to test a dewar is to measure the Normal Evaporation Rate (NER), which is published for Technifab Dewars
. You’ll find more about NER and testing methods
in our Cryogenic Resource Library.
Product Feature – VJ Tank Switcher
Cryogenic liquid tank switchers for a continuous supply of nitrogen have been around for years. Most recent innovation has been around more sophisticated electronic controls. But those controls don’t address two common complaints of cryogenic tank switchers. Dripping and sweating from the non-vacuum jacketed pipe creates condensation on connections and pipe. This moisture can damage the drywall or other mounted surface. It also takes time for the liquid cryogen to get to the freezer or other device the cryogenic system is feeding.
In 2012 Technifab introduced the first vacuum jacketed cryogenic tank switcher
, which addresses those issues. The heat leak is dramatically reduced keeping the exterior at room temperature by using vacuum insulation on the inlets and tubing. Initial cryogen liquid delivery time is improved by keeping the interior colder longer and reducing the thermal mass during an initial fill. You can find out more about our vacuum jacketed tank switcher on our website
Updated Commerce Website
Our online store, cryodewars.com
, was recently upgraded with more products and made easier to use. Technifab was an early cryogenic pioneer with our website and Internet sales; we started selling dewars online in 2006! Many of our products, particularly custom cryogenic equipment and vacuum jacketed pipe which have lots of options, really aren't sold best through an online website. For standard dewars and cryogenic accessories though, check out the options at cryodewars.com
. You can also pick up the phone if you’d prefer to talk with a person. We’re here from 8 am to 8 pm Eastern time daily.
Over 20 Years of Growth
Noel Short started working in the cryogenic industry in the early 1960’s. In 1992 he decided to start his own company, Technifab Products, Inc. Technifab’s original charter was to manufacture cryogenic equipment and that is still the company’s main focus today. Noel’s first employee was Rob Drake, who is now the V.P. of Manufacturing. They were soon joined by Steve Short, the current President of the company, and then Doug Short who is now V.P. of Sales and Marketing.
With our recent growth, Technifab has about 70 employees in three locations: Indiana, California, and Texas. Today the company is still privately held by Noel, Steve, Rob, and Doug. You can read more about our history
at the Technifab.com website.