Hydraulic Grade Line (HGL) adds which component to determine the Energy Grade Line?

• A. Pressure head
• B. Potential head
• C. Velocity head
• D. Both Potential and Velocity head

Answer: (C)

The Energy Grade Line (EGL) in a hydraulic system represents the total mechanical energy per unit weight of fluid, which includes contributions from different energy components. The Hydraulic Grade Line (HGL) represents the potential energy component of the fluid, specifically the elevation head and pressure head.

To determine the EGL, the velocity head is added to the HGL. This is because the velocity head accounts for the kinetic energy of the fluid. The velocity head is calculated using the formula (v²/2g), where 'v' is the velocity of the fluid and 'g' is the acceleration due to gravity.

By adding the velocity head to the Hydraulic Grade Line (which comprises the elevation and pressure head), you effectively account for all forms of energy in the fluid flow, leading to the complete representation of energy in the Energy Grade Line. Thus, understanding the relationship and contributions of each component clarifies why the velocity head is the correct addition to determine the EGL.