4 replies to this topic

[inkar]

I have a pump that is pumping stable product to a tank. There is no blanketing on the tank and it is not vented to the atmosphere. What will be the pressure in the tank? Will it be due to vapor pressure of the liquid. Since vapor pressure is below atmospheric..will there be vapor in the tank at all? Will the pressure in tank increase as liquid level rises?

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[Pilesar]

You will need to make some assumptions about this problem or get more information. I will not make those assumptions, but will make a few observations: 1) if there is no connection to atmosphere, then atmospheric pressure will not affect the contents of the tank. 2) Cone roof tanks usually are for near atmospheric conditions because of physical limitations of the design. 3) With no blanketing and no venting, what was inside the tank before liquid was introduced? Was it full vacuum or full of air or full of product vapor? 4) When the tank level increases, the vapor will have less space and will either increase in pressure or reduce in volume by becoming liquid. The behavior depends on the vapor and liquid compositions which will usually be different where there is a mixture of components.

Edited by Pilesar, 01 October 2022 - 07:45 AM.

[inkar]

hi pilesar, thanks for reply. If the tank is not vented to atmosphere and no blanketing and if we have small amount of liquid product in the tank, will the tank have pressure = vapor pressure of the liquid....but since at ambient condition vapor pressure (11 psia)< atmospheric pressure (14.7 psia), will there be vacuum inside vessel? As we fill tank vapor gets compressed and pressure start increasing? 

[Pilesar]

If you think of the pressure on the tank walls as 'internal pressure' and 'external pressure' it may avoid confusion when asking 'will there be vacuum inside the vessel.' There will be an absolute pressure inside the vessel which will be the same whether on earth, on the moon, or out in space. As to what happens when vapor gets compressed -- surely the pressure will begin to rise. But then what? Won't the vapor start to condense? There is a dynamic response (the immediate time-sensitive pressure increase) and then there is a steady state result (what would be the conditions if the higher liquid level were left for a long time.) 

[inkar]

thanks pilesar