Scenario: Top-Top hot pump with 36" suction line and 28" pump nozzle. Vertical section of the line is 5-6 m due to layout guidelines and then taking a horizontal turn. Obviously a spring is required at the top elbow to relieve the pump nozzle of the vertical loads.
Now the question is, Will the weight of the liquid in the vertical portion of the line be considered to be supported by the spring or by the pump impeller?
If yes, then we have to change the liquid density to zero for the vertical portion, otherwise the spring selection will be erroneous.