The Energy Grade Line (EGL) is equivalent to which of the following?

• A. Hydraulic Grade Line plus Pressure Head
• B. Hydraulic Grade Line plus Potential Head
• C. Hydraulic Grade Line plus Velocity Head
• D. Potential Head plus Velocity Head

Answer: (C)

The Energy Grade Line (EGL) represents the total mechanical energy per unit weight of fluid flowing in a system. It encompasses all forms of energy present, which include potential energy (elevation head), kinetic energy (velocity head), and pressure energy.

The Hydraulic Grade Line (HGL) is defined as the sum of the potential energy (elevation head) and the pressure energy (pressure head) of the flowing fluid. To determine the EGL, one must add the velocity head, which represents the kinetic energy component to the HGL.

Therefore, when considering the EGL, it is specifically the Hydraulic Grade Line combined with the velocity head that accounts for all forms of energy in the flow system. This reflects how the total energy available to the fluid incorporates not only the potential energy due to elevation and pressure but also the energy associated with its velocity.

In contrast, other options either misinterpret the components that make up the EGL or do not account for the essential kinetic component. By understanding the relationship between the Hydraulic Grade Line and the velocity head, one can accurately identify the correct expression for the Energy Grade Line.