Working Losses formula |
||
| \( L_w \;=\; N \cdot H_{lx} \cdot \left( \dfrac{\pi}{4} \cdot D^2 \right) \cdot K_n \cdot K_p \cdot K_b \cdot W_v \) | ||
| Symbol | English | Metric |
| \( L_w \) = Working Losses | \(lbf \;/\; yr\) | \(Pa\) |
| \( N \) = Stock Turnover Rate | \(turnover \;/\; yr\) | \(turnover \;/\; yr\) |
| \( H_{lx} \) = Stock Maximum Liquid Height | \(ft\) | \(m\) |
| \( \pi \) = Pi | \(3.141 592 653 ...\) | \(3.141 592 653 ...\) |
| \( D \) = Tank Diameter | \(ft\) | \(m\) |
| \( K_n\) = Woking Loss Turnover Factor | \(dimensionless\) | \(dimensionless\) |
| \( K_p\) = Woking Loss Production Factor | \(dimensionless\) | \(dimensionless\) |
| \( K_b\) = Venting Setting Correction Factor | \(dimensionless\) | \(dimensionless\) |
| \( W_v \) = Stock Vapor Density | \(lbm \;/\; ft^3\) | \(kg \;/\; m^3\) |
Working losses, abbreviated as \( L_w \), from fixed roof tanks are the vapor emissions that occur during the operational activities of filling or emptying the tank. These losses are caused by the displacement of the vapor space within the tank as liquid is added or withdrawn. When liquid is pumped into the tank, the rising liquid level compresses the vapor above it, increasing internal pressure and forcing vapor out through vents or seals. Conversely, when liquid is removed, the vapor space expands, potentially drawing in outside air, which can mix with the remaining liquid and lead to further evaporation over time. The extent of working losses depends on factors such as the volatility of the stored liquid, the rate of filling or emptying, the tank’s design (including vent and seal configurations), and the frequency of operations. These losses are a significant component of total routine losses from fixed roof tanks and are typically calculated using standardized methods.
