“OK- So you recommend venting cryogenic liquid cylinders and portable vessels down “fully” after filling. But- Doesn’t this waste product?”
Answer: Define “product.”
If the “product” you are referencing is liquid oxygen, nitrogen or argon then No. Venting off gas created during the fill process will actually help preserve liquid in your 4L DOT Liquid Cylinder, Medical Liquid Oxygen delivery vessel or other portable container. The fact is that the gas in the vessel that you would be venting off has already been lost and is no longer liquid product.
Remember- Pressure building tends to be an accelerating curve the higher the pressure in you vessel the shorter the time before you start venting. If you vent down all the way back to right at zero then you stabilize the liquid in your tank moving you back away from the venting time point. You also remove gas which is by definition hotter than liquid. Getting this gas out also helps remove energy that raises the temperature of your liquid product. As a last point- A filled vessel with pressure on it also has a potential to push liquid into the venting system which will boil off and create pressure.
If the “product” you are referencing is gaseous oxygen, nitrogen or argon then you might be wasting a little product. BUT- this is only true if you plan to immediately use the vessel and you will be able to harvest the oxygen, nitrogen or argon gas right away for cutting, purging or some other use. If you are not using it right away then leaving gas pressure in the vessel will just lead to faster venting and the product will be lost anyhow. You will also lose additional gas created by liquid boiling off sooner than it needed to.
Answer: Define “product.”
If the “product” you are referencing is liquid oxygen, nitrogen or argon then No. Venting off gas created during the fill process will actually help preserve liquid in your 4L DOT Liquid Cylinder, Medical Liquid Oxygen delivery vessel or other portable container. The fact is that the gas in the vessel that you would be venting off has already been lost and is no longer liquid product.
Remember- Pressure building tends to be an accelerating curve the higher the pressure in you vessel the shorter the time before you start venting. If you vent down all the way back to right at zero then you stabilize the liquid in your tank moving you back away from the venting time point. You also remove gas which is by definition hotter than liquid. Getting this gas out also helps remove energy that raises the temperature of your liquid product. As a last point- A filled vessel with pressure on it also has a potential to push liquid into the venting system which will boil off and create pressure.
If the “product” you are referencing is gaseous oxygen, nitrogen or argon then you might be wasting a little product. BUT- this is only true if you plan to immediately use the vessel and you will be able to harvest the oxygen, nitrogen or argon gas right away for cutting, purging or some other use. If you are not using it right away then leaving gas pressure in the vessel will just lead to faster venting and the product will be lost anyhow. You will also lose additional gas created by liquid boiling off sooner than it needed to.
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