Standing Losses formula |
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| \( L_s \;=\; 365 \cdot K_e \cdot H_{vo} \cdot \left( \dfrac{\pi}{4} \cdot D^2 \right) \cdot K_s \cdot W_v \) | ||
| Symbol | English | Metric |
| \( L_s \) = Standing Losses | \(lbf \;/\; yr\) | \(Pa\) |
| \( K_e \) = Vapor Space Expansion Factor | \(dimensionless\) | \(dimensionless\) |
| \( H_{vo} \) = Vapor Space Outage (Tank Roof to Liquid Surface) | \(ft\) | \(m\) |
| \( \pi \) = Pi | \(3.141 592 653 ...\) | \(3.141 592 653 ...\) |
| \( D \) = Tank Diameter | \(ft\) | \(m\) |
| \( K_s \) = Vented Vapor Saturation Factor | \(dimensionless\) | \(dimensionless\) |
| \( W_v \) = Stock Vapor Density | \(lbm \;/\; ft^3\) | \(kg \;/\; m^3\) |
Standing losses, abbreviated as \( L_s \), also called breathing losses, from fixed roof tanks are the vapor emissions that occur due to the natural expansion and contraction of the vapor space within the tank caused by daily temperature and atmospheric pressure fluctuations. These losses happen even when the tank is not being filled or emptied, as the stored liquid and vapor respond to external environmental changes. During the day, rising temperatures cause the liquid and vapor inside the tank to expand, increasing internal pressure and forcing vapor to escape through vents or seals. Conversely, at night, cooling temperatures cause the vapor to contract, drawing in outside air, which can lead to further evaporation over time. The magnitude of standing losses depends on factors such as the volatility of the stored liquid, the tank's design (e.g., vent settings, roof seals), and local climate conditions, particularly temperature swings.
