Centrifugal pumps are machines which use centrifugal force to move liquids. In this program, you will learn the principles, parts, and general operation of these pumps, what pump efficiency is, and how head and pressure are calculated.

1. Centrifugal pumps
Petroskill course
Hector Nguema Ondo Perez

2. Introduction to centrifugal pumps
Introduction to centrifugal pumps
• From Low elevations to high
elevations
• From Low pressure to high
pressure areas
• To increase the flow rate
Pressure and Head: Head is the height of a liquid
Pressure Gauges

3. Introduction to centrifugal pumps
Suction lift system
• The higher the vapor pressure, the more readily the liquid
vaporizes
• To keep liquid at the pump from vaporizing, the absolute
suction pressure must be higher than the liquid's vapor
pressure at that temperature
The vapor pressure of a liquid is the equilibrium pressure of a
vapor above its liquid (or solid); that is, the pressure of the vapor
resulting from evaporation of a liquid (or solid) above a sample of
the liquid (or solid) in a closed container

4. Introduction to centrifugal pumps
Capacity
Pump capacity is the amount of liquid that the pump moves in a given length of time
• Can be changed by increasing pump speed, also speed
of the driver, or increasing the impeller size
Horsepower
• Horsepower (HP) is a unit used for measuring rate of work
Pump efficiency =
Pump volumetric efficiency is a measure of its internal leakage

5. Introduction to centrifugal pumps
Net Positive Suction Head (NPSH)
• Net positive suction head (NPSH) is the absolute
suction head minus the vapor pressure head.
• NPSH available is the absolute pressure at the pump
suction, converted to head, minus the vapor pressure
of the liquid being pumped, converted to head.
• NPSH required is the minimum head needed at the
suction to get the liquid into the impeller
without vaporizing
NPSH available must be more than NPSH required
• When the absolute suction pressure increases, the NPSH available increases.
• When the vapor pressure increases, the NPSH available decreases.
• When the suction head decreases, the NPSH available decreases
• When the suction head increases, the total head decreases.
• When the discharge head increases, the total head increases

6. Introduction to centrifugal pumps
Performance curves
• As the pumping rate increases, NPSH required increases.
• As the flow rate increases, horsepower required increases.
• The efficiency of a pump is relatively low at high and low flow rates

7. Design of centrifugal pumps
Centrifugal pumps
• Centrifugal force is the force of spinning
• A centrifugal pump operates by increasing the velocity, or
speed of a liquid.

8. Design of centrifugal pumps
Pumps are classified according to:
• Number of stages.
• Impeller design
Type of centrifugal pumps
• Single or double suction.

9. Design of centrifugal pumps
• Propeller pumps
 The propeller blades whirl the liquid to high speed in a straight line path. These high-speed
pumps have low heads, and can handle large capacities.
Type of centrifugal pumps
• Liquid leaves in the same direction it entered.
• Liquid enters the pump through the blades.
• The area through which liquid enters is larger and
can handle larger capacities

10. Design of centrifugal pumps
• Turbine Pumps
 The flow of liquid through a turbine pump is halfway between the flow through a centrifugal
pump and the flow through a propeller pump. As the liquid enters the pump, it circulates
around and around, gaining additional pressure each time it passes the turbine blades
Types of centrifugal pumps
The best features of the impeller pump and the propeller pump are combined in the turbine
pump. Turbine pumps generally have a high head and high discharge pressure for their
size and speed.

11. Design of centrifugal pumps
Type of centrifugal pumps
• Turbine pumps generally have a high head and high discharge pressure for their size and speed.
• Propeller pumps have low heads, and can handle large capacities

12. Design of centrifugal pumps
Series and Parallel operation
• When the discharge of one pump is fed into the suction
of another pump, the two pumps operate in series. This
increases the discharge head of the system.
• Pumps that discharge into the same line are operating
in parallel. Operating pumps in parallel increases the
capacity of the system because the total amount
discharged is the combined sum of the amounts
discharged from both pumps

13. Components of centrifugal pumps
Wear Rings, Packing Box and Lantern Rings
Wear Rings
• Maximize efficiency by reducing the leaking.
• Minimize the cost of pump maintenance.
• Replaceable periodically during the pump life.
Packing Box
• Provide a seal to reduce leakage.
• Filled with a flexible, low friction and non-abrasive material.
• Shaft part is protected by a removable sleeve.
Lantern Rings
• Around the shaft sleeve inside the packing box.
• Provides space where the lubricating or seal oil can be supplied

14. Components of centrifugal pumps
Mechanical seals and sealless pumps
• Require less maintenance and hold leakage to a minimum.
• The springs push against the compression ring and compress the o-ring
against the shaft and the rotating seal members, which prevents leakage.
• The pump and motor are housed within the same casing.
• Rotating magnetic field that causes the rotor to move, or
rotate.
• They contain no seals, they are more resistant to leakage than
pumps with a packing box or a mechanical seal.

15. Components of centrifugal pumps
Impeller Thrust and Balancing Drums
• Any leakage into the collar flows back into the
suction through a hole in the impeller, which
equalizes pressure between the left and right
sides of the impeller
• The total impeller thrust is the sum of the thrust of all the
impellers.
• The pressure acting on the left side of the balancing drum is
the pump discharge the right side of the balancing drum is a
suction pressure.
• Balancing drum balance the impeller thrust eliminating axial
thrust.

16. Operation of centrifugal pumps
Pumps alignment and pump cooling
• Puts a strain on the shaft and may wear or
break the shaft or couplings.
• May cause bearings and seals to wear
excessively or fail.
• May damage wear rings and permit the impeller
to rub against other parts.
• May cause excessive vibration.
• Heavy-duty and hot liquids pumps may be water-jacketed to
cool the lubricating oil.
• Shaft and packing are often fitted with water jackets as
well. The cooling water circulates in the water jacket
surrounding the packing box.

17. Operation of centrifugal pumps
• Wear rings : simplify maintenance by protecting the casing and the impeller
• Packing Box: Must be always lubricated.
– Ring Packing lubricated by the liquid being pumped
– Lantern ring and packing are lubricated by oil.
• Bearings and Couplings
Lubrication
There is almost no friction
between the balls and any of the
other parts they touch because of
the lubrication.
Used in large pumps. Has more
surface area than a ball bearing
and can support a very heavy
shaft.
Used in pumps with a large axial
load. The shoes are pivoted to
absorb minor variations in the
rotation of the collar.

18. Operation of centrifugal pumps
• Priming: The process of removing the air or gas from the pump and filling the casing with liquid.
Pump Priming
• This pump may be primed by venting
the air or gas from the casing
Removing the air or gas from the pump
creates a vacuum inside the pump.

19. Thanks for coming.
Any Questions?
Hector Nguema Ondo Perez