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Pumps and Pumping in Irrigation applications Basic Pump Theory Basic Pump Theory John Starke: Irri – Gator Products.

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Presentation on theme: "Pumps and Pumping in Irrigation applications Basic Pump Theory Basic Pump Theory John Starke: Irri – Gator Products."— Presentation transcript:

1 Pumps and Pumping in Irrigation applications Basic Pump Theory Basic Pump Theory John Starke: Irri – Gator Products

2 What do Pumps pump? Slurry - Liquids - Gases - etc oils oils petroleum petroleum water water fertiliser fertiliser liquid foods liquid foods sewerage sewerage air air etc-etc etc-etc

3 What type of pumps are there? Centrifugal – single or multi stage Centrifugal – single or multi stage Positive displacement Positive displacement Rotary Rotary Peristaltic Peristaltic Axial flow Axial flow Turbine Turbine Vacuum Vacuum Piston Piston etc-etc etc-etc

4 Pumps Commonly found in Irrigation Centrifugal = used for pumping water Centrifugal = used for pumping water Positive displacement rubber screw (Mono) = Positive displacement rubber screw (Mono) = lower volume high pressure = pumping water lower volume high pressure = pumping water Piston type very low volume – precise = Piston type very low volume – precise = fertiliser injection fertiliser injection Turbine = pumping water Turbine = pumping water Submersible – multistage – low to med volume + higher pressures = borehole Submersible – multistage – low to med volume + higher pressures = borehole Submersible – single stage – high volume + low pressure = dewatering Submersible – single stage – high volume + low pressure = dewatering

5 Concentrate on Centrifugal Pumps for pumping Irrigation water. What is a Centrifuge or Centrifugal force?

6 A is: A Centrifuge is: a piece of equipment - generally driven by a motor - that puts an object in rotation around a fixed axis applying a force - perpendicular to the axis.

7 Centrifugal & Centripetal Forces

8 Centrifugal Pumps A centrifugal pump is one of the simplest types of pump that uses centrifugal force to move fluid into a pipe. A centrifugal pump is one of the simplest types of pump that uses centrifugal force to move fluid into a pipe. The basic purpose of the pump is to convert energy of an, or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped. The basic purpose of the pump is to convert energy of an electric motor, or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped. Centrifugal pumps are the most commonly used pump and their operating cost is low compared to other pumps. Centrifugal pumps are the most commonly used pump and their operating cost is low compared to other pumps. They are reputed for high reliability and ensure smooth operation. They are reputed for high reliability and ensure smooth operation.

9 Centrifugal Pump Delivery Flange Backing Plate Bearings Gland Packing Volute Casing Impeller Suction Flange Shaft Pedestal

10 Pump Terminology Duty Point = a certain flow of water at a certain pressure to fulfil the system requirement – constant or varying Duty Point = a certain flow of water at a certain pressure to fulfil the system requirement – constant or varying Pump Efficiency = how effectively the pump converts the input energy into water pressure Pump Efficiency = how effectively the pump converts the input energy into water pressure Rotational Speed = Speed at which the Impeller turns Rotational Speed = Speed at which the Impeller turns Positive Suction = The water flows into pump on its own e.g. below dam wall Positive Suction = The water flows into pump on its own e.g. below dam wall

11 Pump Terminology Negative Suction = The pump has to lift the water from a source lower than itself e.g. river Negative Suction = The pump has to lift the water from a source lower than itself e.g. river NPSH = refers to the maximum lift capability a pump has to extract water from a source lower than itself NPSH = refers to the maximum lift capability a pump has to extract water from a source lower than itself Cavitation = Noise in the Volute Casing of a Pump due to the presence of undesirable air particles imploding Cavitation = Noise in the Volute Casing of a Pump due to the presence of undesirable air particles imploding

12 Pump Identification & Pump Curves Pump Manufacturer – e.g. KSB; Rapid Allweiller; GrundfosPump Manufacturer – e.g. KSB; Rapid Allweiller; Grundfos Pump Type - Single Stage - 65/250; 80/40; 150/315 etcPump Type - Single Stage - 65/250; 80/40; 150/315 etc Multistage - 80/40 – 2 stage; WKLN 65/4 etc Multistage - 80/40 – 2 stage; WKLN 65/4 etc Impeller Size – e.g. 250mm; 185mmImpeller Size – e.g. 250mm; 185mm Motor Size – kilowatts or horsepowerMotor Size – kilowatts or horsepower Speed of Motor – 2 / 4 Pole or 29?? / 14?? RPMSpeed of Motor – 2 / 4 Pole or 29?? / 14?? RPM Efficiency of motor – ?Efficiency of motor – ? Power factor of motor – cos ?Power factor of motor – cos ?

13 Typical Motor Identification Plate

14 Typical Pump Identification Plate

15 What is a Pump Curve? Pressure / Head Developed Pressure / Head Developed Flow rate of liquid Flow rate of liquid Power Duty point and Non overload Power Duty point and Non overload NPSH required NPSH required Efficiency of pump Efficiency of pump This is the characteristics of the pump when operating at a specific speed and giving the following info:

16 65 / 250 Centrifugal Pump Head in Metres Flow rate in m³ per hour120m^3/hour 82m

17 kW Power 37kW Power 80

18 82 meters head 71% efficiency Nett pump suction head required is 4,6m Motor size required for non overload is 45 kW 120 m^3/hr

19 Laws of Affinity The affinity laws express the mathematical The affinity laws express the mathematical relationship between the several variables involved in pump performance. They apply to all types of centrifugal and They apply to all types of centrifugal and axial flow pumps. They are as follows: They are as follows:

20 Volume Capacity The volume capacity of a centrifugal pump can be expressed as: The volume capacity of a centrifugal pump can be expressed as: q = (n1 / n2) x (d1 / d2) q = (n1 / n2) x (d1 / d2) Where: Where: q = volume flow capacity (m³ / hour) q = volume flow capacity (m³ / hour) n = wheel velocity - revolution per minute - (rpm) n = wheel velocity - revolution per minute - (rpm) d = wheel diameter – (mm) d = wheel diameter – (mm)

21 Head or Pressure The head or pressure of a centrifugal pump can be expressed as: The head or pressure of a centrifugal pump can be expressed as: h = (n1 / n2)² x (d1 / d2)² h = (n1 / n2)² x (d1 / d2)² Where: Where: h = head or pressure (metres) h = head or pressure (metres)head

22 Power The power consumption of a centrifugal pump can be expressed as: The power consumption of a centrifugal pump can be expressed as: P = (n1 / n2)³ x (d1 / d2)³ P = (n1 / n2)³ x (d1 / d2)³ Where: Where: P = power (kilowatt) P = power (kilowatt)

23 Changing the Impeller Speed If the Impeller diameter is constant - change in Impeller speed can simplify the affinity laws to: If the Impeller diameter is constant - change in Impeller speed can simplify the affinity laws to: Volume Capacity Volume Capacity q1 / q2 = (n1 / n2) q1 / q2 = (n1 / n2) Head or Pressure Head or Pressure dp1 / dp2 = (n1 / n2)² dp1 / dp2 = (n1 / n2)² Power Power p1 / p2 = (n1 / n2)³ p1 / p2 = (n1 / n2)³

24

25 If the speed of a pump is increased with 10% then: the volume flow increases with 10% the volume flow increases with 10% the head increases with 21% the head increases with 21% the power increases with 33 % the power increases with 33 % If we want to increase the volume of an existing system with 10% we have to increase the power by 33%. If we want to increase the volume of an existing system with 10% we have to increase the power by 33%.

26 How NOT to do it !!

27 How many of these do we see ? !!

28 Pump House or Store Room? Time for an Upgrade ??!!

29 Rather do THIS !!!

30 Or This !

31 Sell some of these!!!!

32 Thanks


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