Centrifugal pumps sizing
Pump application Data sheetTo size a pump, you must define: • The flow rate of liquid the pump is required to deliver The total head of a system (Step by Step A-B-C) A) Static Head (HS): Static head represents the net change in height, in feet, that the pump must overcome. B) Friction Head: When fluid flows through any system, friction is caused by resistance in the piping, fittings and valves called friction head. This is also called pressure drop Use of Hoses in pumps suction and discharge Most food and beverages industries uses hoses in their transfer process. Many people don't take into consideration the "friction loss" due surface roughness on the inside of the hose. longer hoses, coils and curves increase friction loss and "reduce the pump performance". Tips
Example: One pump is drawing water from an open tank to another open tank 7 feet above the pump at 50 GPM. Suction and discharge tube diameter is 1 ½”. Find the total head under these conditions: Solution:
Why “head” instead psi?
How can I convert feet to psi? For example a Sugar syrup @ 60 Brix, have an specific gravity of 1.29 Convert 90 feet of head to psi : The pressure of a column of water is about 0.433 psi per foot of column height. Why is the discharge pipe diameter of a centrifugal pump smaller than the suction pipe? A centrifugal pump apply centrifugal force to generate velocity this force converts the energy by accelerating the fluid between suction and discharge, the outlet has a higher velocity due the small area of the tri-clamp compared with the Suction area, but the flow is the same. Suction lines are generally designed to keep friction losses to a minimum and the discharge size is determined by the head generated by the friction losses and cost considerations. Specific Gravity: Is the weight of liquid in comparison to water at approximately 68°F (SG =1). Water column: Is the pressure exerted by a vertical column of water inside of a well casing or a pipe, measured at the bottom of the column.
We need to know the “duty point” Duty point: The point on the curve where the flow and head match the application's requirement is known as the duty point.
Pump Terminology Head: Static Head Total Head / Total Dynamic Head: Capacity/Flow BHP (Brake Horsepower) and Capacity BHP Is the total power required by a pump to do a specified amount of work. NPSH (Net positive Suction Head) Cavitation: Vapor Pressure: Viscosity: Friction Loss: Impeller: Volute: |
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