How do hospitals get their oxygen supply?
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Liquid oxygen is stored outside the facility in a giant cylinder and shit loads of plumbing at 50psi.
Am respiratory therapist, part of my job is knowing how that works and having the keys to shut it off.
1) Oxygen canisters ordered at supplier.
2) Oxygen canisters delivered by supplier.
3) Oxygen canisters connected at hospital.
The oxygen can be bought commercially in liquid form. Manufacturers have multi-step refrigerators that can go to very low temperatures. Basically you put one refrigerator inside another to get colder temperatures. The last step is usually a sterling cycle cooler which can make oxygen go liquid. Air from the outside is first filtered and dried in order to remove most of its impurities. Then it is cooled down so it condenses into liquid air. The problem with this is that air is mostly nitrogen with some oxygen and a few other gasses. But nitrogen have a higher boiling point then oxygen which is used to separate these gasses. When the air is cold enough for nitrogen to condense but not cold enough for oxygen to condense you get oxygen gas and liquid nitrogen. So the providers usually sell both liquid oxygen and liquid nitrogen as well as argon which is separated in a similar way. Any excess gasses that is produced is just vented. Hospitals can then buy the liquid oxygen which is delivered in specially insulated tanker trucks and stored in special tanks outside the hospital. As it boils the oxygen is collected into pipes through regulators and heaters to all the hospital beds.
There is also some mobile oxygen separators which are sometimes used. Especially when moving patients around it can be easier then using a gas bottle. These use a molecular sieve to filter out oxygen from the nitrogen. Basically the oxygen molecules are slightly bigger then the nitrogen molecules so you can make a sieve that allows nitrogen to pass but not oxygen.
Industrial gas are extracted from air we breath, these are done at gas plants. Each type of gas like oxygen, nitrogen, carbon dioxide etc has each individual boiling point where a certain temperature and pressure level will become liquid gas state.
Once the required gas are extracted and in liquid form it then get transported off to sites and hospitals via lorries with storage tanks.
A cup of liquid gas can fill a whole room in gas form so transporting via liquid form works great. Imagine ikea foam mattress, when compressed with no air in foam you could transport much more than a mattress fill with air.
Once liquid gas arrive on site, it will be off loaded to storage pressure cylinder in liquid form. When required It will then be heated and liquid gas would expand into gas form and fill a separate storage for usage. These stored oxygen in gas form will then fill smaller storage vessels that can be carried or wheeled into hospital rooms.
Depending on the geographic locations and ambient temperature, the liquid gas could be heated using the ambient vaporisers where liquid gas runs through series of piping with fins to boil the liquid. These type of vaporiser will tend build up in ice over a period of operation and needs to be switched off to melt the ice build up.
Other type of vaporiser are using heating elements like jet engine using methane gas to boil the liquid gas in large quantities. These are costly and tend to be used for docks receiving gas supplies from abroad. I live in UK and we get methane gas from the Middle East by under water pipe and ships.
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