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Tank Vapor Space Volume

Tank vapor space volume, abreviated as \(V_v\), is the empty area within a storage tank that is not occupied by liquid.  It's the volume above the liquid level in a fixed roof tank.  This space contains a mixture of air and the vapors of the stored liquid.  

Tank Vapor Space Volume formula
\( V_v \;=\;  \left( \dfrac{\pi }{ 4 } \cdot D^2 \right) \cdot H_{vo} \) 
Symbol English Metric
\( V_v \) = Tank Vapor Space Volume \( ft^3 \) \( m^3 \)
\( \pi \) = Pi \(3.141 592 653 ...\) \(3.141 592 653 ...\)
\( D \) = Tank Diameter \(ft\) \(m\)
\( H_{vo} \) = Vapor Space Outage \(ft\) \(m\)
The vapor space volume can fluctuate due to various factors. When liquid is pumped into the tank, the vapor space decreases, compressing the vapors and increasing the pressure.  Conversely, when liquid is withdrawn, the vapor space expands, causing the pressure to decrease.  Temperature changes also impact the vapor space, heating the liquid generates more vapors, increasing pressure, while cooling causes vapors to contract, reducing pressure.

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