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WA9302-CS 950612 SHIMEK, JACOBS & FINKLEA CONSULTING ENGINEERS 8333 Douglas Avenue,//820 Dallas, Texas 75225 (214) 361-7900 Ross ,AcoBs. b , O } RONALD V. CONWAY, P.E. JOHN W. BIRKHOFF, P.E. JOE R. CARTER, P.E. GARY C. HENDRICKS, P.E. June 12, 1995 C. L. SHIMEK, P.E. I. C. FINKLEA, P.E. JAMES E. LAUGHLIN, P.E. Mr. Howard Pafford Water Uti ' ~es Superintendent City of oppell }~"t/~tY°r~~~758019 Re: Village Parkway Pump Station Expansion Pump Selection Dear Mr. Pafford: As you are aware, and as provided in our engineering services agreement for this project, the final selection of the pumps for the Village Parkway Pump Station Expansion is the responsibility of the City of Coppell. However, since we have converted your water system analysis database to the Cybernet format, we were easily able to prepare system curves for your use and aid in the selection of the proper pumps for the hydraulic condition and design parameters specified. We are enclosing one copy each of system-head curves we developed for the Village Parkway Pump Station Expansion project. The system curves were developed using the Cybernet Hydraulic model and the water system data we converted from the recent Kimley-Horn water system report. These system curves were developed on the basis that the pump station expansion is to serve as a system operational enhancement rather than to add system pumping capacity. For that reason, when evaluating the system head curve, we assumed in all alternatives and design years that the following conditions applied: 1) No other pumps in the system are running. This includes the 3-450 horsepower pumps at Village Parkway Pump Station and the future Belt Line Road Pump Station scheduled to come on line in the year 2004. If the proposed pumps (pumps no. 5 & 6) are to provide operational flexibility and not system capacity, then this seems to be a reasonable assumption. Basing the pump selection on this condition will assure a pump that has the highest efficiency under the most probable operational situation. This is not to say however, that the proposed pumps will not operate properly when the other pumps are running, just that they won't likely be operating at their most efficient point. 2) That the proposed pumps would primarily be operated during off-peak times. This generally applies to minimum hour demand periods during the summer time when the elevated storage is not being re-filled, and during the wet months of late fall, winter and early spring. Using this assumption, a system-curve was develop for each design year utilizing the minimum hourly demand period data set. This data set was Mr. Howard Pafford City of Coppell June 12, 1995 Page No. 2 developed from the average day demand data contained in the Kimley-Horn Report and is roughly equivalent to 80% of the average day demand. Another reason for using the minimum hourly demand period as the basis of the system curve development is that during this period of the system operation the highest system heads are normally experienced. We have also made a preliminary pump selection based on the system curves we developed and on the information we were able to derive from the City' s water system analysis report. Reviewing the output data from the hydraulic analysis of the distribution system, we found that for most operating conditions the proposed pumps were delivering in the range of 2,600 to 3,000 gallons per minute. This delivery rate was based on proposed pumps rated at 250 horsepower each. Using the delivery rate as a basis of pump selection, we reviewed several Worthington horizontal split case pumps and found the model 8LR-20 with a 17-inch impeller, or the model 10LR-14 with a 14.17-inch impeller, to be best suited for this application. Based on the system curves we developed and the Worthington pumps identified above, we recommend the either one (but not both) of the design requirements shown below be included in the pump specifications for this project: Village Parkway Pump Station Expansion Proposed Pumps No. 5 & 6 Operating Points Based on Design Year 1995 Worthington 8LR-20 Worthington 10LR-14 Duty Point Duty Point Duty Point Duty Point Duty Point Duty Point Q (gpm) 3, 100 3,500 3,700 2,000 2,700 4,200 Total Dynamic Head (fi) 217 200 184 220 210 185 Minimum Efficiency 80% 78% 76% 65% 78% 86% Pump Speed: 1,770 rpm 1,770 rpm Shutoff Head - Maximum 315 Ft. 260 Ft. Shutoff Head - Minimum 290 Ft. 240 Ft. Maximum BHP 250 Hp. 250 Hp. We have plotted both the Worthington, model 8LR-20 and model 10LR-14 pump curves on the system curve for each design year. The Worthington pumps were used as the basis for pump selection due to their existing service in the Village Parkway Pump Station, however many other pump manufactures have pumps that offer similar operating characteristics. We recommend the specifications for this project allow no less than three pump manufactures of equal experience, quality and service capabilities. Mr. Howard Pafford City of Coppell June 12, 1995 Page No. 3 Please review the enclosed system-head curves and the operating points we have chosen as the basis of pump selection for this project and notify us of your findings. We are available to discuss this project further at your convenience. Sincer y y, urs, ks, P.E. Enclosure cc: vK~neth M. Griffin, P.E.