Exploring the Role of Cryogenic Neck Tubes in Cryogenic Applications: Ensuring Safety and Efficiency

Published on March 18, 2024

The word “cryogenic” comes from two Greek words, “kryos” and “genic,” which, when put together, roughly translates as “to produce frost.” On the surface, this indicates that cryogenics can thus be described as a science that deals with temperatures below the freezing point of water (0°C or 32°F). In actuality, the science of cryogenics deals with much lower temperatures. This goes back to a Dutch professor named Kamerlingh Onnes at the University of Leiden, who used the word to describe the science of cryogenics as involving temperatures far lower than water’s freezing point.   

In 1877, the French physicist Louis Paul Cailletet liquified oxygen by bringing it to a temperature of -183°C (-297.4°F). Before this, scientists believed that such “permanent” gases, including argon, carbon monoxide, hydrogen, nitrogen, and oxygen, couldn’t exist as liquids. By 1908, all these “permanent” gases were liquified, including helium, which was only discovered as an element in the 1890s. Today, the US National Institute of Standards and Technology (NIST) considers cryogenics to include a range of temperatures from -180°C (-292°F) to zero degrees Kelvin, a temperature also known as absolute zero (-273.15°C or -459.67°F).

Understanding Cryogenic Systems 

The science of cryogenics requires special infrastructure to handle extremely cold materials. Cryogenic systems involve an array of special containers, fluids, piping, pumps, and other equipment. Infrastructure for cryogenics has developed significantly over time and has become increasingly complex, with stronger materials, better insulation, and cutting-edge engineering for dealing with liquified gases.

James Dewar developed a key piece of equipment for cryogenic systems in the late 19th century, a storage container now known as a dewar.  Dewar also first utilized a vacuum as insulation to help contain materials at temperatures that are considered cryogenic. Systems that handle cryogenic materials now use vacuums to insulate transfer lines and other equipment. Using a special container to handle and vacuum insulating extremely cold materials are key elements within any cryogenic system.

The basic components of a cryogenic system include: 

  • Compressors: These specially-made compressors must handle cryogenic temperatures as they typically transport gases to the low-pressure part of a system, facilitating the refrigeration process by allowing gas to expand to atmospheric pressure without heating substantially.
  • Container: A specially designed container, such as a dewar, that minimizes heat transfer and features robust insulating capabilities is necessary to store cryogenic fluids; usually, these are dual-walled with a vacuum dividing the outer and inner walls to reduce heat transfer.
  • Fluids: Cryogenic systems typically rely on liquid forms of helium, hydrogen, nitrogen, or oxygen, all of which have boiling points under -150°C (-238°F).
  • Heat exchangers: These exchangers transfer heat from one fluid to another, allowing gases to cool so they liquefy and can be used within the cryogenic system.
  • Piping: Transporting cryogenic fluids between storage containers requires well-insulated piping or transit lines that keep heat gain minimal.
  • Pumps: Specialized cryopumps are designed to operate at low temperatures to move fluids or gases through the cryogenic system.
  • Sensors: It’s essential in a cryogenic system to control and monitor the fluids’ temperatures, including temperature sensing devices like resistance temperature detectors and thermocouples.
  • Valves: Controlling the flow with a cryogenic system, valves must be made from materials that can withstand cryogenic temperatures.
  • Controls: Modern cryogenic systems often use computer-based controls or programmable logic controllers (PLCs) to automate monitoring and regulation of factors like flowrates, pressures, and temperatures.

As extremes of temperature can damage equipment or harm personnel, cryogenic systems also feature a safety system. These deal with risks like fire hazards from oxygenated substances, leaks, and too much pressure. These vulnerabilities are mitigated by safety components, including emergency shutdown instruments, pressure relief valves, and sensors to detect escaping gases.

Neck Tubes in Cryogenic Systems

Neck tubes are integral to cryogenic systems. They’re particularly important when working with dewar or other cryogenic storage containers. Neck tubes keep the dewar suspended within a vacuum isolated from the cryogenic fluids. As noted earlier, this vacuum provides insulation to keep energy loss to a minimum. At the same time, the neck tubes also provide added strength to the structure and insulation within the system.

Neck tubes aid the transfer of cryogenic fluids. They normally have a cylindric body and a narrow neck. Made from composite materials that can withstand extreme cold, neck tubes perform several essential roles. This includes acting as an access point through which cryogenic fluids flow into or out of the dewar. While the vacuum provides insulation for cryogenic fluids, materials out of which neck tubes are made also insulate to minimize heat transfer, which is especially critical at the narrow neck of the tube to prevent fluids from warming.

Many neck tubes also have safety features to relieve pressure, such as burst disks or pressure relief valves, to ensure pressures are kept within the cryogenic system’s limits. Accessories like adapters for imparting cryogenic fluids, pressure gages, or sensors that track temperatures can also be mounted on neck tubes. These help operators control and monitor fluids in the cryogenic system. Neck tubes are essential, allowing access to samples within a dewar or other cryogenic storage container while also providing insulation and safety features for the cryogenic system.

How Neck Tubes Complement Transfer Hoses in Cryogenic Systems

Transfer hoses are essentially the piping for a cryogenic system. These vacuum-jacketed hoses work with neck tubes to safely transfer cryogenic fluids throughout the system. It’s essentially a flexible pipe that connects via a phase separator with the sealed opening of a neck tube, which serves as how these containers are filled or emptied of cryogenic fluids. As with other equipment within a cryogenic system, transfer hoses are designed to withstand high pressures and low temperatures. Typically, transfer hoses are made from stainless steel to allow welding, working with neck tubes to facilitate the transportation of fluids at cryogenic temperatures throughout the system.

Applications for Cryogenic Systems

Cryogenic systems are used for numerous medical and industrial applications. For example, most metals lose electrical resistance below a certain temperature and, in turn, become superconductors.  So cryogenic systems produce extremely powerful magnetic fields that require neither electrical power (once the field is established) nor heat. Made normally from alloys containing niobium cooled to 4.2 K (-268.95°C; -452.11°F), these fields are used for hospitals’ magnetic resonance imaging (MRI) machines.

As the science behind cryogenic systems advances and becomes increasingly sophisticated, the uses for cryogenics are only likely to multiply.

Spaulding Composites for Cryogenic Neck Tubes

Founded in 1873, Spaulding Composites has seen cryogenic systems transform over the last 150 years from experimental uses to many commercial and industrial applications. As a maker of composite materials, the company has considerable experience working with materials that can withstand cryogenic temperatures. These include producing materials for tanks transporting liquid methane and neck tubes used in cryogenic systems. To learn more about us and how we can help your cryogenic application, contact the leaders in composite technology at Spaulding Composites.