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**Pumps and Pumping in Irrigation applications**

Basic Pump Theory John Starke: Irri – Gator Products

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**What do Pumps pump? Slurry - Liquids - Gases - etc**

oils petroleum water fertiliser liquid foods sewerage air etc-etc

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**What type of pumps are there?**

Centrifugal – single or multi stage Positive displacement Rotary Peristaltic Axial flow Turbine Vacuum Piston etc-etc

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**Pumps Commonly found in Irrigation**

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

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**Concentrate on Centrifugal Pumps for pumping Irrigation water**

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

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**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.

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**Centrifugal & Centripetal Forces**

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Centrifugal Pumps 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 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. They are reputed for high reliability and ensure smooth operation.

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**Centrifugal Pump Delivery Flange Backing Plate Suction Flange**

Gland Packing Bearings Shaft Impeller Volute Casing Pedestal

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Pump Terminology 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 Rotational Speed = Speed at which the Impeller turns Positive Suction = The water flows into pump on its own e.g. below dam wall

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Pump Terminology 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 Cavitation = Noise in the Volute Casing of a Pump due to the presence of undesirable air particles imploding

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**Pump Identification & Pump Curves**

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

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**Typical Motor Identification Plate**

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**Typical Pump Identification Plate**

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

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**65 / 250 Centrifugal Pump 82m Head in Metres Flow rate in m³ per hour**

120m^3/hour

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80 120 37kW Power 17kW Power

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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

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**Laws of Affinity They are as follows:**

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

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

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

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**Power The power consumption of a centrifugal pump can be expressed as:**

P = (n1 / n2)³ x (d1 / d2)³ Where: P = power (kilowatt)

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**Changing the Impeller Speed**

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

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**If the speed of a pump is increased with 10% then:**

the volume flow increases with 10% the head increases with 21% 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%.

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How NOT to do it !!

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**How many of these do we see ? !!**

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**Pump House or Store Room?**

Time for an Upgrade ??!!

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Rather do THIS !!!

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Or This !

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Sell some of these!!!!

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Thanks

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Pumps CM4120 D. Caspary February, 2004.

Pumps CM4120 D. Caspary February, 2004.

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