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1 ME444 ENGINEERING PIPING SYSTEM DESIGN CHAPTER 6 : PUMPS
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2 LAST SESSION 1.PIPING SYSTEM DESIGN PROCEDURE 2.PIPE THICKNESS 3.PIPE SIZING AND SYSTEM PRESSURE DROP
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3 CONTENTS 1.Fundamental of Pumps 2.Operating Point 3.Pump Selection 4.Pump Installation
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4 1. Fundamental of Pumps When source pressure is not enough to provide desired output, pump is utilized. SOURCEPIPING SYSTEMEND USERS
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5 Pump output Flow rate and Pressure rise. Flow rate
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6 Pump input and output Output = Flow rate and Pressure rise. Flow rate Input energy
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7 Specific Speed
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8 Pump performance Dynamic pump Positive displacement pump
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9 Pump performance range
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10 Performance curves = 0.57 (N s = 1,550) = 3.66 ( N s = 10,000)
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11 Steep vs. flat curves Flat curve for closed loop system with variable flow rate Steep curve for high head and constant flow rate
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12 Affinity law Impeller DiameterImpeller Speed
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13 Example of performance curves
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14 Example of performance curves
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15 Speed of induction motor polesSynchronous speed (rpm) Possible Operating Speed (rpm) 230002850 415001425 61000950 8750712 10600570
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16 Standard motor size hpkW 1/80.09 1/60.12 1/40.18 1/30.25 1/20.37 3/40.55 10.75 1.51.1 21.5 2.51.85 32.2 hpkW 43 5.54 7.55.5 107.5 1511 2015 2518.5 3022 4030 5037 6045
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17 Effect of Fluid Viscosity
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18 Net Positive Suction Head
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19 Net Positive Suction Head Required At low pressure, water can become vapor, causing cavitations. Temperature T ( o C) Vapor Pressure (kPa)** 00.87 50.92 101.18 202.29 304.27 407.43 5012.36 6019.89 7031.10 8047.32 9070.16 100101.3 Suction pressure must be maintained above NPSHR to avoid cavitation
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20 Net Positive Suction Head Available z Suction lift Vapor pressure Pressure drop in suction piping MUST Maintain NPSHA > NPSHR
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21 2. Operating Point Pump performance curve System pressure drop curve Operating point
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22 Filling a tank from bottom Pump performance curve
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23 Filling a tank from bottom vs. from top Which way fill faster?
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24 Throttling the discharge valve Pump performance curve Fully open valve Throttled valve
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25 Variable speed drive vs. valve throttling Pump performance curve N1 Throttled valve Fully open valve Pump performance curve N2 Feedback signal
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26 VSD for pressure control Valve 1 and 2 open Pump performance curve N2 Pump performance curve N1 Pressure set point All valve open Pressure signal
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27 Limitation of VSD Cannot reduce speed System curve Feedback signal
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28 Parallel and Serial Connection
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29 Response to Parallel Connection
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30 Parallel Connection of Pumps with Different Size
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31 Utilization of Pressure Tank Pressure Switch Pressure Tank Air Water time Pressure in tank Pump operate Pump stop
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32 3. Pump Selection Best Efficiency Energy cost is far beyond the pump cost
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33 Example 6.1 Select the suitable pump for Example 5.1 200 lpm @ 50.85m.WG.
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34 Example 6.1 (2) 200 lpm 50.85 m Possible selections: NM12 and NM25/20
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35 Example 6.1 (2) Select NM12: Trim Diameter to 198 mm
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36 Example 6.1 (3) Select NM12: Trim Diameter to 198 mm Pump has efficiency of 49.5% Power consumption 3.2 kW Max power consumption 4kW Select Motor size: 5.5kW Note: follow standard motor size
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37 Example 6.1 (4) hpkW 1/80.09 1/60.12 1/40.18 1/30.25 1/20.37 3/40.55 10.75 1.51.1 21.5 2.51.85 32.2 hpkW 43 5.54 7.55.5 107.5 1511 2015 2518.5 3022 4030 5037 6045
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38 Example 6.1 (5) Dimension of NM12
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39 Example 6.2 Back to example 5.3, if two identical pump of the following curve is installed, predict the operating point. 900lpm@23.1m.WG.
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40 Example 6.2 (2) 23.1m.WG. = 21.6m.WG Variable with flow rate + 1.5 m. WG. Elevation Constant
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41 Example 6.2 (3) 2 pumps in parallel Single pump
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42 3. Pump Installation
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43 Typical Installation
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44 Suction Lift More suction lift = Less NPSHA Cavitation 5 Meter lift is the maximum possible value Foot Valve Submersible pump
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45 Pumping from Tank Vortex prevention plate Drain Mak-up Vent Overflow
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46 Eccentric Reducer INCORRECT CORRECT
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47 Installation photos
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48 Installation photos
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49 Homework Exercise 6.1 and 6.2
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50 Case Study
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