98 Mar B5 May 2012 Page 5 Of 20 Question 4 Pump Application Refer To The Examination Paper Attachments Page 14 Pump Ch 1 (70.34 KiB) Viewed 35 times
98-Mar-B5-May 2012 - Page 5 of 20 QUESTION 4 PUMP APPLICATION Refer to the Examination Paper Attachments Page 14 Pump Characteristics and Page 15 Cavitation Parameter. 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 Ls 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 (0) Maximum elevation of pump relative to supply level (g) Efficiency of pump (h) Electric power consumption [ 10 marks ]
98-Mar-B5 - May 2012 - Page 14 of 20 QUESTION 4 PUMP CHARACTERISTICS . VO (N.)si = 0.2 0.3 0.5 1.0 1.5 2.0 3.0 4.0 100 95 90 85 80 75 Efficiency 77,% Axtal- Radial-flow Mbred-flow 70 flow 2.5 65 2.0 60 1.5 pe 55 1.0 50 0.5 45 LIEU 0.0 1000 0,000 N, -Vepm ii Axds of rolation Figure 15.11 Optimum efficiency and typical values of , for water pumps as a function of specific speed.
98-Mar-B5 - May 2012 - Page 15 of 20 QUESTION 4 CAVITATION PARAMETER VO (N.) - (eh) 34 0 1.0 2.0 3.0 4.0 1.6 1.4 1.2 1.0 Critical cavitalon parameter o== (APSH). 0.8 0.6 0.4 02 2000 4000 6000 6000 10,000 12,000 /gpm Specific speed based on gpm, N, - ne Figure 15.12 Approximate values of critical cavitation parameter qe as a function of specific speed.
Join a community of subject matter experts. Register for FREE to view solutions, replies, and use search function. Request answer by replying!