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 !
Or &#; How to Dodge Dewar Bullets
The old saying really goes something like:
To know someone is to love them
If people count on you to supply liquid nitrogen or other cryogenic liquids for storing biological samples or processes like Liquid Chromatography Mass Spectrometry (LCMS) and Molecular Beam Epitaxy (MBE), the saying can apply to your relationship with your dewars and liquid cylinders.
Because, most of the time, things are good.
But when things go bad (you unexpectedly run out of liquid, liquid stops flowing, or your floors get water damaged), the more familiar you are with the operations and maintenance of your dewars and liquid cylinders, the faster you can make things better.
This post will reacquaint you with a key piece of equipment - dewars and liquid cylinders &#; so that you can quickly solve problems and resolve issues that keep you away from you numerous #1 priorities.
Tomāto, Tomăto &#; Dewar or Liquid Cylinder
Many people use the word &#;dewar&#; to describe a &#;liquid cylinder&#;, and vice versa. There are some key differences.
Are you interested in learning more about Dewar Tank Sizes? Contact us today to secure an expert consultation!
What is a Liquid Cylinder?
Liquid cylinders are pressurized containers specifically designed for cryogenic liquids. Liquid cylinders let you withdraw liquid and/or gas.
A liquid cylinder has valves for filling and dispensing the cryogenic liquid, and a pressure-control valve with a brittle rupture-disk as backup protection.
What is a Dewar?
Dewars are non-pressurized vessels, like a Thermos Bottle. They typically have a loose fitting cap or plug that prevents air and moisture from entering, yet allows excess pressure to vent.
Laboratory dewars have wide-mouthed openings and do not have lids or covers. Laboratories primarily use these small containers for temporary storage.
The remainder of this post focuses on Liquid Cylinder operations.
Know Your Gauges, Circuits and Valves
To help you see the forest from the trees, take a look a the diagram below to become familiar with the important parts of your liquid cylinders.
Pressure Gauge
The Pressure Gauge is probably the one you will look at first and refer to most frequently. This gauge indicates gas pressure inside the inner tank.
Since cryogenic liquids are actually liquefied gases, pressure within the tank will constantly increase as the laws of physics transform the cold liquid into warmer gas. Fortunately, this pressure will help you withdraw the liquid or gas from your cylinder. But for most applications, the pressure inside the tank must be artificially maintained. A Pressure Building Circuit can automatically do that.
Opening the Pressure Building Valve located at the top of the tank takes liquid from a line that runs from the bottom of the inner tank, and passes it through the Pressure Building Coil attached to the inside wall of the outer tank. As liquid passes through the Coil, it is vaporized by the heat of the outer tank. The resulting gas is fed through the Pressure Building Valve and Pressure Building Regulator, into the inner tank causing the pressure to rise.
Gas-use Valve and the Vaporizer Circuit
When pressure has been built, you can draw gas from your cylinder by opening the Gas-use Valve. Opening this valve lets the pressure in the tank force liquid up a withdrawal line, and then down into a vaporizer coil. Once again, heat is conducted through the outer tank walls to the vaporizer. As the liquid moves through the coil, it is vaporized by this heat. The resulting warm gas flows up through the Gas-use Valve out to the user system to complete the Vaporizer Circuit.
Generally a single stage regulator is attached directly to the Gas-use Valve to reduce the supply pressure to match your application&#;s requirements.
Economizer Circuit
If you don't use the a cylinder for several days, pressure will continue to rise at a rate of 30 psi per day because a small amount of heat will leak into the inner tank. This heat vaporizes a small amount of liquid and causes the pressure to slowly rise. The pressure may build up to the design of your Pressure Control Valve. The valve will then open and vent gas to the atmosphere.
To minimize losses from this venting, the cylinders have an Economizer Circuit. The Economizer Circuit come into action when the pressure reaches 100 40 psi. At this point, the regulator allows gas from the top of the tank to flow through the internal vaporizer out of the Gas-use Valve to the your target system. This reduces pressure in the inner tank and minimizes losses from venting. When pressure normalizes, the Economizer Regulator closes and the cylinder then deliveries gas by drawing liquid through the Vaporizer Circuit. The Economizer Regulator should have a set pressure 15 psi higher than the Pressure Building Regulator.
Pressure Control Valve and Rupture and Burst Discs
The Pressure Control Valve is mounted on the same stem as the Pressure Gauge. Often set to open at 230 psi, the Pressure Control Valve works in conjunction with a Rupture Disc in the inner tank. As a secondary relief device, there is also a Burst Disc on the outer tank to protect the space between the inner and outer tanks from high pressure.
Liquid-use Valve
To withdraw liquid from your cylinder, first close the Pressure Building and Gas-use Valves. Then open the Liquid-use Valve to allow head pressure in the tank head to force liquid up to withdrawal tube, and out the Liquid-use Valve.
Liquid withdrawal should be done at low pressure to prevent flash losses. During transfer, if pressure in the tank is higher than the normal liquid withdrawal pressure, open the Vent Valve to lower the pressure. Before withdrawing liquid, liquid is typically withdrawn at less than 15 psi.
When filling an open container, if a greater liquid withdrawal pressure or rate is required, a qualified service agent can adjust the Pressure Building Regulator.
Don&#;t get Caught Dry: Liquid Contents Gauge
In the center of the tank there is a Liquid Contents Gauge. This can be a float-type gauge that provides an approximate indication of the tanks contents.
If you want more accurate measurements, try a gauge that uses differential pressure of determine liquid levels. These modern displays also contain graphical digital displays to give you precise measurements. Plus they often have the intelligence to eliminate the need for lookup charts.
In addition, many of these digital liquid content gauges have telemetry capabilities to make it easier to monitor levels of key cylinders.
Watch out for Frost and Water
Because the Pressure Building Vaporizer contains cold liquid, it cools the outer tank and it is perfectly normal for frost to form on the outside of the cylinder. During a prolonged high-draw, the gas-withdrawal temperature to fall considerably and the outside of the cylinder will be very heavily frosted.
This frost eventually turns to water that can damage flooring, as well as seep into your facility&#;s interstitial space to create more damage to other systems.
A Drip Tray can save you a lot of headaches and hassles. Place your liquid cylinder and/or its vaporizer on a pan or tray to catch the water as the frost evaporates. The higher the tray&#;s lip, the less worry you&#;ll have about water damage.
So What?
The more you know about your dewars and liquid cylinders, the less you have to worry about them.
If you think something has gone wrong, just remember:
- The Pressure Gauge indicates pressure inside the inner tank. Opening the Pressure Building Valve increases tank pressure to normal operating levels.
- The Gas-use Valve allows gas to flow from the tank.
- The Economizer Circuit minimizes product loss.
- To draw liquid, close the Gas-use and Pressure Building Valves, and open the Liquid-use Valve.
- If you need to know exactly how much liquid is in your cylinder, use a Digital Gauge.
- Frost and ice are nothing to be scared about. But use a drip tray or pan to avoid water damage.
But if you do need help, make sure that your liquid nitrogen, argon or helium is set-up to get you a solution when you need it. Whether it be an emergency delivery, or just being talked through a problem, a good cryogenic supplier like But if you do need help, make sure that your liquid nitrogen, argon or helium is set-up to get you a solution when you need it. Whether it be an emergency delivery, or just being talked through a problem, a good cryogenic supplier like WestAir is good to have around. Contact us today for a quote and consultation.
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