98-Mar-B5 May 2016 Page 3 of 22 QUESTION 2 PUMP APPLICATION Refer to the Examination Paper Attachments Page 11 Pump Char

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98 Mar B5 May 2016 Page 3 Of 22 Question 2 Pump Application Refer To The Examination Paper Attachments Page 11 Pump Char 1 (70.51 KiB) Viewed 28 times

98-Mar-B5 May 2016 Page 3 of 22 QUESTION 2 PUMP APPLICATION Refer to the Examination Paper Attachments Page 11 Pump Characteristics and Page 12 Cavitation Parameter. Use the SI units on these charts. A centrifugal pump is required to pump potable water from a water treatment plant to a reservoir for subsequent distribution. The required flow is 85 L/s and the head 30 m. The pump will be driven by an induction motor operating at 60 Hz and 400 V with a slip of 3% and electrical losses of 4%. To ensure satisfactory operation basic preliminary design information is required. Assuming that the head loss in the pump inlet piping is 1.0 m and that the vapour pressure under the prevailing conditions is 2 kPa, determine the flowing: (a) Pump specific speed (b) Type of pump and sketch of impeller (c) Diameter of impeller (d) Critical cavitation parameter (e) Desired net positive suction head (1) Maximum elevation of pump relative to supply level (9) Efficiency of pump (h) Electric power consumption Show on the attached diagrams on Page 11 and Page 12 where data has been obtained and return these pages with your answer booklet. (10 marks ]
98-Mar-B5 May 2016 Page 11 of 22 EXAMINATION PAPER ATTACHMENTS NAME QUESTION 2 PUMP CHARACTERISTICS w.vo (N)SI = (gh)34 1.0 1.5 0.2 0.3 0.5 2.0 3.0 4.0 100 95 η n -1-1 90 ZA 85 80 75 Efficiency n. % Radial-flow Mixed-flow Axial- flow 70 2.5 65 2.0 60 de 1.5 de 1.0 55 50 0.5 45 DJ 0.0 10,000 Coo'c n. Vgpm N, = h34 1 Axis of rotation BER Optimum efficiency and typical values of d, for water pumps as a function of specific speed.
98-Mar-B5 May 2016 Page 12 of 22 NAME QUESTION 2 CAVITATION PARAMETER WVO (Ne)sı - (sh) 0 1.0 2.0 3.0 4.0 1.6 1.4 1.0 Critical cavitation parameter 04 – (NPSH). 0.8 0.6 0.4 0.2 0 2000 4000 6000 8000 10,000 12,000 gpm Specific speed based on gpm, N, - ne h34 Approximate values of critical cavitation parameter o as a function of specific speed.