Maximum Surge Pressure for Fluid Formula |
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\( p_s \;=\; \dfrac{ p_w \cdot \Delta V \cdot W }{ 144 \cdot g }\) (Maxium Surge Pressure for Fluid) \( p_w \;=\; \dfrac{ 144 \cdot p_s \cdot g }{ \Delta V \cdot W }\) \( \Delta V \;=\; \dfrac{ 144 \cdot p_s \cdot g }{ p_w \cdot W }\) \( W \;=\; \dfrac{ 144 \cdot p_s \cdot g }{ p_w \cdot \Delta V }\) \( g \;=\; \dfrac{ p_w \cdot \Delta V \cdot W }{ 144 \cdot p_s }\) |
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| Units | English | Metric |
| \( p_s \) = Maxium Surge Pressure for Water | \(ft\) | - |
| \( p_w \) = Pressure Wave Velocity | \(lbf-ft\;/\;sec\) | - |
| \(\Delta V \) = Water Velocity Change | \(ft^3\;/\;sec\) | - |
| \( W \) = Unit Weight of Fluid | \(lbf\) | - |
| \( g \) = Gravitational Acceleration | \(ft \;/\; sec^2\) | - |
Maximum surge pressure for fluid is the peak pressure increase in a fluid system caused by a sudden change in fluid velocity, such as when a valve closures rapidly, a pump stops, or a pipe is obstructed. This occurs because the kinetic energy of the moving fluid is converted into pressure energy, creating a pressure wave that propagates through the system at the speed of sound in the fluid.
The magnitude of the maximum surge pressure depends on factors like the fluid’s density, the velocity change, the speed of the pressure wave, and the system’s pipe material and geometry. The Joukowsky equation is commonly used to calculate this pressure surge. For example, in a gasoline pipeline, a sudden stop could generate a surge.
