Everything You Need to Know About Liquid Nitrogen Dewars

Introduction: Why Liquid Nitrogen Dewars Matter

Liquid Nitrogen Dewar is a powerhouse in science, industry, and medicine. But storing and transporting this cryogenic liquid safely? That’s where the liquid nitrogen dewar comes in. These specialized containers are essential for preserving biological samples, freezing materials, and even powering some futuristic cooling systems. Whether you’re a lab tech or a science geek, understanding dewars is key to working safely with LN2 (liquid nitrogen).

What Is a Liquid Nitrogen Dewar?

A liquid nitrogen dewar is a vacuum-insulated container designed specifically to hold and transport liquid nitrogen at extremely low temperatures typically -196°C (-321°F). Named after Scottish scientist Sir James Dewar, who invented the vacuum flask in the 1890s, dewars keep LN2 cold and contained without the need for mechanical refrigeration.

How Does a Dewar Work?

The magic lies in the vacuum insulation. This double-walled structure limits heat transfer from the outside environment, which helps prevent the nitrogen from boiling off too quickly. Some dewars even have multiple layers of reflective foil to reduce radiant heat transfer.

Types of Liquid Nitrogen Dewars

1. Storage Dewars

These are ideal for long-term holding of LN2. They’re commonly used in labs and medical facilities.

2. Transport Dewars

Designed for safe movement of LN2 from one location to another. They are usually more rugged and portable.

3. Withdrawal Dewars

These feature spouts or siphons for easily dispensing the liquid nitrogen.

Key Features to Consider

When choosing a dewar, here’s what to look out for:

• Capacity: Ranges from a few liters to 50+ liters.
• Holding Time: How long the LN2 remains liquid.
• Build Quality: Stainless steel or aluminum with rugged exteriors.
• Ease of Use: Ergonomic handles, pressure valves, and pouring spouts.
• Safety Features: Pressure-relief devices to prevent over-pressurization.

Common Applications of Liquid Nitrogen Dewars

Scientific Research

Cryopreservation, cryogenics studies, and superconducting magnets often rely on dewars.

Medical and Biotech

Storing vaccines, sperm, eggs, and other biological specimens at ultra-low temps.

Industrial Uses

Used in metal fabrication for shrink-fitting and cooling mechanical components.

Food and Beverage

LN2 helps create novelty items like nitrogen ice cream or rapid freezing of gourmet dishes.

Safety Tips for Handling Liquid Nitrogen Dewars

Working with LN2 is serious business. Here are a few essential safety measures:

• Always wear protective gear (face shield, cryo-gloves, apron).
• Use dewars in well-ventilated areas to prevent oxygen displacement.
• Never seal a dewar tightly, as pressure build-up can lead to explosions.
• Use proper lifting technique or carts for larger containers.

Storage Best Practices

• Keep dewars upright at all times.
• Avoid direct sunlight or extreme heat sources.
• Regularly inspect for damage or leaks.
• Store away from flammable materials.

Maintenance and Care

Maintaining your dewar means extending its lifespan and ensuring safety:

• Clean with warm water and mild detergent no abrasives!
• Check for vacuum integrity if LN2 boils off too quickly.
• Replace worn-out seals or gaskets.
• Have pressure valves tested periodically.

How Long Does LN2 Last in a Dewar?

It depends on the size and quality of insulation, but typically, a good dewar can keep LN2 for anywhere from a few hours to several weeks. For example, a small 5-liter dewar may hold LN2 for 5–7 days, while a 50-liter unit may last up to 60 days.

Buying Guide: Choosing the Right Dewar

Not sure which model to pick? Consider these questions:

• What is the intended use (transport, storage, dispensing)?
• How often will you refill it?
• Will it be stationary or mobile?
• Is there easy access to refill stations?

Top manufacturers to consider include Thermo Fisher Scientific, Worthington Industries, MVE, and Cryofab.

Conclusion

A liquid nitrogen dewar is a must-have tool for anyone working with LN2 whether it’s for science, medicine, industry, or even culinary innovation. Choosing the right one boils down to knowing your needs, staying safe, and maintaining it well. With proper use, a quality dewar can last for many years and make your cryogenic operations smoother and safer.

FAQs

1. Can I transport a liquid nitrogen dewar in a car?
Yes, but only if it’s well-ventilated and the dewar is secured upright. Never transport sealed dewars due to pressure risks.

2. How do I know when to refill my dewar?
Check the weight or use a dipstick. Some models also have digital level indicators.

3. Is it dangerous to touch liquid nitrogen?
Yes! Direct contact causes severe frostbite. Always use protective gear.

4. Do I need special training to use a dewar?
Basic cryogen safety training is recommended, especially in workplaces and labs.

5. What’s the lifespan of a liquid nitrogen dewar?
With proper care, a high-quality dewar can last 10–20 years or more.