Dewar or pressurized tank - which to choose?

With Cryomed cryosaunas, you have two options for liquid nitrogen storage and feed &#; non-pressurized Dewar containers or larger pressurized cryogenic tanks. In most cases, they are not interchangeable. Therefore, before buying a cryosauna, it is crucial to choose the type most suitable for your needs.

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What is a Dewar? 

A cryo Dewar is a two-walled vacuum flask capable of keeping a relatively constant temperature of a cryogenic liquid over a long period. Design-wise, Dewars are big thermos bottles with loose-fitting caps. 

Cryogenic Dewars are a good fit for cryotherapy centers with low to moderate customer flow. As a rule, Cryomed&#;s open-top cryosaunas come with two 35-liter non-pressurized tanks or, optionally, with two 50-liter tanks. If you expect more than ten cryo-goers daily, you might want to opt for pressurized cryogenic liquid cylinders. 

Cryosauna Cryomed Pro (Dewar type)

What is a cryogenic
storage cylinder?

Cryosauna Cyomed Pro Ultra (pressurized tank type)

A liquid nitrogen cylinder is a pressurized vacuum-jacketed tank. It features valves for refilling and withdrawing liquid nitrogen, a pressure release valve and a pressure indicator for safety. In addition, a cylinder is fitted with a float level gauge to control the liquid nitrogen consumption. 

Cryogenic Dewars vs. pressurized cryogenic storage tanks 

Though both tanks serve the same purpose, non-pressurized Dewars and pressurized liquid nitrogen cylinders differ from each other in: 

Size

Non-pressurized Dewar tanks are smaller and easier to handle. In Cryomed Pro or Cryomed Basic, a cryo Dewar is rolled into the cryosauna. In smaller models, like Cryomed One or Cryomed Mini, a Dewar sits next to the device.  When not in use, Dewars can be stored in a utility room.

A pressurized cryo cylinder always stays outside a cryosauna. In smaller premises, a tank can sit in another room or even outside the building. The cryotherapy machine and the tank are linked by a standard two-meter cryogenic hose.  However, Cryomed&#;s team can always find a suitable solution for your location, so feel free to reach out.

Weight

A 35-liter Dewar container weighs 17 kg when empty and comes with a wheeled platform, making it easy to move. In some countries, you can put it in your car and get it refilled at your supplier&#;s. However, in the majority of cases, such tanks get refilled at your place from a specialized truck. 

Pressurized tanks are heavier and more large-sized. They are always refilled or replaced with a full tank at your place. Make sure to consult your supplier about any restrictions linked to your location in advance. If your business is on the 3rd floor in an old high-rise building without a heavy-duty elevator, Dewars may be a safer bet.

Evaporation rate

Pressurized tanks have a higher evaporation rate than non-pressurized cryo Dewars. In addition, nitrogen gets lost along the hose and on the junctions between the valve and the hose and between the tank and the hose. However, with a high customer flow, this loss is negligible.

For reference, pressurized tanks evaporate 2 to 5% of their capacity, depending on the manufacturer. Non-pressurized Dewars used by Cryomed  evaporate 0.5% of their capacity. 

Usually, manufacturers estimate the evaporation rate conservatively. The most reliable way to assess holding time is to track actual daily weight changes. Used cryo tanks have a higher evaporation rate.

Price

Liquid nitrogen cylinders are expensive. Their  price tag can easily reach up to several thousand euros, depending on their capacity and manufacturer. That&#;s why many cryopreneurs prefer renting cryo cylinders from local nitrogen suppliers.

A Dewar costs between 1,000 EUR and 1,500 EUR. Depending on your customer flow and nitrogen supply terms, you might need to buy more Dewars in addition to the two tanks you get together with a cryosauna. 

Number of sessions

As nitrogen consumption affects the number of sessions you can get out of your cryogenic container and, eventually, the session cost, there are a couple of things to bear in mind. 

Consumption of liquid nitrogen in cryogenic tanks depends on:

• The session time (1.5 to 3 minutes).
• The session temperature (for a first-timer, the operator can choose -110&#;; for a veteran user, -150&#;). 

You can save nitrogen by scheduling sessions one by one with no more than 10-minute gaps in between.

• The evaporation rate from liquid nitrogen tanks. The higher the room temperature, the more nitrogen you lose daily. 

That is why the number of sessions you can get from one cryogenic container is tentative. 

Standard non-pressurized Dewar tanks have a 35-liter capacity, sufficient for one cooling and up to 8 treatment sessions. It is a good choice if you expect up to ten customers per day or buy a cryosauna for home use.

Pressurized tanks vary in capacity from 100 to 5,000 liters, but the most usual option is 240 liters. Out of a 240-liter tank, you can have some 60 sessions.

A cryogenic liquid cylinder is a convenient and cost-effective option that does not require frequent refills. It is most suitable for businesses with high customer flow, like a gym, a spa, or a clinic.

How to choose between a Dewar and a nitrogen tank?

Now that you are clued in on the two types of cryogenic vessels, let&#;s see how to make the best choice. 

Dewar vs pressurized tank &#; which to choose?

• The expected number of daily sessions is decisive. The higher the customer flow, the more nitrogen you need. In this case, pressurized nitrogen tanks are a more convenient option. Cryogenic Dewars are suitable for cryopreneurs with up to 10 customers a day. 

• Access to your cryotherapy treatment room is the second most important factor.  With stairs or high floors with no elevator Dewars are a more viable solution. A flight of two or three stairs can be covered with a board you can roll the tank over, but anything higher makes the delivery of a pressurized tank impossible. 

• Another factor to consider is the rental and delivery fee for cryogenic liquid cylinders in your area. Situations may be different. 
  • A supplier may refuse to sell small batches or refill non-pressurized tanks, so you will have to rent bulk cryogenic containers, notwithstanding the low customer flow in your cryo center.
  • A supplier may be located too far and, therefore, charge high delivery fees. In this case, it may be cheaper to rent a cryo cylinder, which does not require frequent refills. 

That&#;s why it is crucial to find a local liquid nitrogen supplier and clarify their pricing and supply terms before you buy a cryosauna. 

• Legal regulations in your country may restrict the use of large-volume cryo cylinders. For example, Italy and Switzerland require a powerful supply-and-exhaust ventilation system in the cryotherapy treatment premises, which may cost over 10,000 EUR to install. This forces the majority of cryopreneurs to opt for a Dewar-based cryosauna instead.  

Both types of cryogenic containers have their pros and cons. Our sales department is always happy to make your choice easier based on our extensive experience. Give us a ring or drop us a message on ! 

Cryogenic tanks are an optimal solution in cases where large quantities of gas need to be stored in liquid form, such as Liquid Oxygen, Liquid Nitrogen, Argon, C02, LNG, LPG, Liquid Hydrogen, etc.

What are the benefits of using cryogenic tanks?

Cryogenic tanks are a type of industrial storage tank boasting a range of strengths, related to aspects such as internal distribution, loading and safety.

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Better internal distribution and optimisation of resources

Cryogenic tanks are very versatile, allowing for the installation of a centralised network for the optimal distribution of the different cryogenic gases used. An important advantage of this type of tank is that there is no gas return to the plant, as is the case with other systems such as cylinders. It goes without saying that this translates into resources saved.

Improved loading process

The loading of the gases into the cryogenic tanks is done using vaporisers. The major benefit of this system is that the liquid gas passes directly from the production plant to the user, avoiding sudden movements and improving stability and safety.

Higher purity

The gas stored in cryogenic tanks maintains a higher level of purity than in other storage systems, as it always remains isolated in a hermetically sealed tank meaning that no possibility exists of contamination with any external agents.

Increased safety

Risks are kept to a minimum, as the gas remains isolated in hermetically sealed, stable tanks with no contact with the outside world. Cylinder transfer within the facilities is avoided, avoiding unnecessary hazards.

Main components in tanks for cryogenic liquids

A cryogenic tank is composed of a structure divided into two fundamental parts:

• An inner vessel made of stainless steel and designed to withstand very low temperatures.
• An outer vessel made of carbon steel.

The two vessels are insulated from each other by a combination of insulating materials. 

In addition to these two containers separated by insulating material, cryogenic tanks are equipped with another vital component: a pressure regulation system. This system is specifically designed to ensure that the cryogenic tank always operates at a constant pressure that is set with the user&#;s needs in mind.

Safety requirements for cryogenic tanks

Tanks for storing cryogenic gases follow very strict safety requirements and protocols, in order to avoid any type of accident that may cause leaks, material damage and, above all, personal injury. Here are some of the main safety measures: 

• All cryogenic tanks are constructed with a double wall: an inner vessel and an outer vessel, which acts as an encasing. In addition, they are separated by an intermediate chamber that acts as a thermal insulating element, which ensures that the cryogenic fluids are always at the right temperature.
• These tanks are equipped with relief valves and rupture or bursting discs, which automatically release the gas in the event of an unforeseen pressure increase. This ensures that the pressure is constantly maintained at the correct levels.
• Not only is storage safe, so is transport, which is carried out in tankers that are also double-walled and vacuum insulated by means of an inter-chamber.

Types of cryogenic tanks depending on the gas they store

A huge variety of cryogenic tanks exists, each perfectly adapted to the cryogenic liquid they have to hold, as well as to where they are going to be located: size, place, terrain, etc.

Cryogenic tanks will therefore have different shape and design characteristics depending on whether they contain: 

Some examples of this type of projects that we have carried out are:

At Cryospain, we&#;re very proud of our team of experts, who boast a wealth of experience in the design, manufacture, assembly and commissioning of low-pressure liquefied gas storage tanks. Add to this the advanced technical resources at our disposal and the result is cryogenic tank supply and design 100% tailored to the needs of each of our clients.

If your project needs gas storage solutions designed and built by true experts, why not contact us today? 

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