403 - Centrifugal Pumps Flashcards
Components of Centrifugal Pumps:
Shaft Discharge Nozzle Bearing Housing Seal Gland Valve Casing Suction Nozzle
Pump Performance Curves
A pumping system operates where the pump curve and system curve intersect.
It is impossible for one operating point to meet all desired operating conditions.
System drives the pumps.
By plotting the system head curve and pump curve together you can determine:
Where the pump will operate on its curve.
What changes will occure if the system head curve or the pump performance curve changes.
System Curve
Represents the relationship between flow and hydraulic losses in a system.
Parabolic in shape.
Is the change in flow with respect to the head of the system.
Developed by the user based upon the conditions of service.
Pump Performance Curves
A pumps capacity i.e. flow rate is plotted against its developed head.
Also shows effiecency (BEP), required input power, NPSHr, speed(RPMs), pump size and type, impeller size.
Generated by test performed by the manuf.
Plotted for a constant speed, S.G. of 1.0, and a given impeller diameter.
NPSHr
Net Positive Suction Head Required
Head required by the pump manf. at the inlet of the pump.
It is a function of the pump design, and would vary from manf. to manuf.
NPSHa
Net Positive Suction Head available
Size: 3*4-13 means
3” discharge
4” suction
13” max impeller dia.
HP curves are by
Electric motors
BHP
Break Horsepower
If we dont get NPSHr we will have:
Cavitation
TDH
Total Developed Head
Change in pressure in feet = Discharge pressure - Suction pressure
Types of Non-Postivive Displacement Pumps:
Variable Displacement Vane Pump
Variable Displacement Radial Displacement Pump
Variable Displacement Bent Axis Pistion Pump
Variable Displacement In-Line Pistion Pump
Types of Circuits:
Regeneration Meter-In Meter-Out Syncronization in Parallel Syncronization in Series Pressure Reducing Counterbalancing Sequencing
