Excessive up-thrust on line shaft turbines is caused by

Excessive up-thrust on line shaft turbines is caused by

• A. Misalignment Of Shaft
• B. Pumping Too Much Water
• C. Too Small Or Worn Impeller
• D. Vertical Clearance Between Bottom Of Pump Bowl And Impeller Is Too Small

Answer: (B)

Excessive up-thrust on a line shaft turbine comes from operating with too much water, meaning the pump is moving more flow than it was designed to handle. As the flow rate increases, the hydraulic forces acting on the impeller grow, creating a larger axial (along the shaft) reaction force. This axial thrust pushes the rotor upward along the shaft, producing the up-thrust condition. The other factors typically cause different issues: misalignment mainly causes lateral vibration and bearing loads, not a consistent axial thrust; a too-small or worn impeller changes efficiency and head but doesn’t inherently increase axial thrust; and a very tight clearance between the pump bowl and impeller can cause rubbing or mechanical binding rather than a hydraulic axial thrust rise. So pumping more water than intended is the primary driver of excessive up-thrust in this setup.

Excessive up-thrust on a line shaft turbine comes from operating with too much water, meaning the pump is moving more flow than it was designed to handle. As the flow rate increases, the hydraulic forces acting on the impeller grow, creating a larger axial (along the shaft) reaction force. This axial thrust pushes the rotor upward along the shaft, producing the up-thrust condition. The other factors typically cause different issues: misalignment mainly causes lateral vibration and bearing loads, not a consistent axial thrust; a too-small or worn impeller changes efficiency and head but doesn’t inherently increase axial thrust; and a very tight clearance between the pump bowl and impeller can cause rubbing or mechanical binding rather than a hydraulic axial thrust rise. So pumping more water than intended is the primary driver of excessive up-thrust in this setup.