Water Well Journal
Issue link: https://read.dmtmag.com/i/767379
Table 1. Design Notes and Rules of Thumb Suggested Checklist for Submersible Pump System Design to Wellhead Estimated eff. = 65% at flows < 200 GPM 1. System analysis: Verification of preliminary design or final COS Estimated eff. = 75% at flows > 200 GPM a. Determination of the primary design flow (Q) and/or alternate(s) Q TDH = sum of 1, 2a, 2b, 3, 4 b. Determination of total dynamic head (TDH) from item nos. 1-4 (below) 1. Well lift + sum of pump losses, riser pipe/check valve/wellhead H f 2a. + system static pressure no. 1 (i.e., typical [normal] closed-loop pressure) -and/or- 2b. + system static pressure no. 2 (i.e., elev. from well to highest point in system) Typical inline devices 3. + Miscellaneous TDH components: (vel. H d , inline device(s), piping, grid h f , etc.) Pressure filters/screens 4. + Future: Reserve H d (wear? well lift? system/piping h f ? pressure?) Sand separators, etc. 2. Pump: Final COS to various bowl diameters/designs (Q usually governs) Use consistent units: Q = capacity a. COS Q —Pump capacity (in flow units, such as GPM, CFS, m 3 /hour, etc.) COS = Conditions of service b. COS H —Pump head-TDH (in head units, such as feet, meters, etc.) c. Pump bowl: If possible, examine up to 4-5 different units? from 2-3 manufacturers Best: Use largest diameter of bowl > 3 stages 1. Pump bowl: Model/diameter from Q/no. of stages/efficiency window? With VFD: Use steep pump curve 2. Pump curve details: HP, BEP range, runout and/or Q/H shutoff issues? Is efficiency reduction required < 3 stages? 3. Is bowl a preassembled factory unit or built as a "per stage" unit? Use NEMA fit motor when possible 4. NEMA fit onto motor? Motor HP and diameter required? Is it available? Use for high head or crooked well 5. Alternate bowl features: (wear rings, static/dynamic balanced impellers, Verify alternate features are available stage O-rings/gaskets, discharge head size and connection, thrust transfer)? HP = kW × 1.34/kW = HP × .746 d. Submersible motor: Required motor horsepower/kW? Rem. largest dia. of motor = high eff. 1. Motor model: Diameter options: 4, 6, 8, 10 inches > 12 inches/NEMA fit? Common 3VAC: 208,230,460,575 2. Required/available voltage and phase?/avoid tandem construction Use soft start/stop: VFD w/RPM rejects 3. Start considerations: VFD/soft start/stop?/inrush amps and ramp U/D times? Minimum VFD frequency = 30 Hertz 4. Miscellaneous considerations: Motor thrust ratings/50 Hz derate/genset rated? WATER WORKS from page 33 waterwelljournal.com 34 January 2017 WWJ