Positive Displacement Pumps

Centrifugal Pumps

Centrifugal Pumps 8 9 1.Casing, volute 2. Impeller, vanes, vane tips, backplate, frontplate (shroud), back vanes, pressure equalising passages 3. Back cover parallel to Plane of the impeller intake 4. Stuffing Box - Gland/mechanical seal housing, packing/lantern ring 5. Pump shaft 6. Pump casing 7. Bearing housing 8. Bearings 9. Bearing seals 8 9

Centrifugal Pumps

Parts of a Pump Prime Mover - drives the pump Steam Electric motor Gear driven from an engine Human Shaft - connects the pump to prime mover Pump Mechanism - converts the energy provided by the prime mover the flow energy

Pump Curve for a Positive Displacement Pump

Simple Positive Displacement Pump

Reciprocating Piston Uses a plunger and cylinder design to deliver constant volume of fluid with each stroke. Used in bilge, steering, and emergency feed pumps

Gear Uses gears to deliver a constant volume of fluid with little pressure fluctuation. Used in control oil and lubricating pumps

Rotary Screw Similar to a gear pump but it operates at a much larger capacity.

Centrifugal Pumps Pumps designed to deliver various flows based on system discharge pressure Centrifugal pump laws flow is proportional to the speed Pressure (head) is proportional to speed2 Power is proportional to speed3

Pump Curve for a Centrifugal Pump

Fluid is drawn into the suction due to a low pressure created as the impeller rotates. The vanes impart momentum upon the fluid. Since the flow rate through the pump is constant, the flow increases due to the increase in cross-sectional area of the vanes. The volute converts the kinetic energy to flow energy as seen in an increase in pressure.

Centrifugal Pump Placement Series - this will increase the pump pressure, but the flow will remain constant. Used to meet NPSH requirements Parallel - this will increase the flow, but the pressure will remain the same. -Used in condesate systems

Jet Pumps They work on the venturi effect Used in air ejectors and eductors