Cryogenic Dewar or pressurized nitrogen tank – which to choose?
Walk-in cryotherapy chambers are always fed from pressurized cylinders. However, with CryoMe’s open-top cryotherapy machines, you have two options: smaller non-pressurized Dewar flasks or larger pressurized cryogenic tanks.
As a general rule, if you expect more than ten cryotherapy sessions daily, pressurized cryogenic cylinders are the better fit. However, other factors may also come into play, e.g., available space, floor level, local regulations on the use of nitrogen tanks in your country, etc.
You are always welcome to consult our sales team to get help in choosing the option better suited to your needs.
What is a Dewar?
A cryo Dewar is a non-pressurized two-walled vacuum tank for cryogenic liquids that can keep a relatively constant temperature over a long time. Design-wise, Dewars are big thermos bottles with loose-fitting caps. Their daily evaporation rate is usually quite low.
Cryogenic Dewars are a good fit for cryotherapy centers with low to moderate customer flow. CryoMe’s open-top cryosaunas come with two 35-liter non-pressurized tanks or, optionally, with two 50-liter tanks.
What is a cryogenic storage cylinder?
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, the tank has a float level gauge to control the nitrogen consumption. It has a higher evaporation rate than non-pressurized tanks.
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 CryoMe Pro or CryoMe Basic, a Dewar is rolled into the cryosauna. In smaller models, like CryoMe One or CryoMe 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. Other hose lengths are available upon request.
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 cylinders 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 CryoMe evaporate 100 to 200 g daily, depending on 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 1,050 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 or using a cabin cover set that comes with an adjustable collar and gloves. - 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. Ideally, you need to use the tank up within 4 to 5 days. If you don’t have enough sessions, opt for a tank of a smaller capacity.
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?
Here’s what defines which nitrogen tank would be best for your business:
- The expected number of daily sessions is the key factor. 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 cost of cryogenic liquid cylinders in your area. These costs can vary significantly, so it is important to evaluate them in advance. That’s why you should find a local liquid nitrogen supplier and clarify their pricing and supply terms before purchasing a cryosauna. Situations may vary:
- A supplier may refuse to sell small batches or refill non-pressurized tanks, so you will have to rent bulk cryogenic containers, even with a 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.
- 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 WhatsApp to get free advice.