BWW EXHIBITION 2012 Sharing of experience Kuek Eng Mong Group Engineers Malaysia Sdn Bhd
CASE 1 DO NOT OVER ESTIMATE SYSTEM HEAD FOR PUMP SELECTION Use Reasonable C value. Hf 6.78xL( m) V ( m / s) 1.165 ( ) (110) D m C 1.85
SAMALAJU RW TRANSFER PIPE, ACTUAL OPERATING HEAD 116M. Samalaju L = meter 28000 28000 28000 28000 28000 Pipe dia. mm d = 800 800 800 800 800 mm 0.788 0.788 0.788 0.788 0.788 Area m2 0.48768828 0.487688277 0.487688277 0.487688277 0.487688 Flow rate MLD Q = 40 40 40 41 40 Velocity m/sec v = 0.94930099 0.949300987 0.949300987 0.973033512 0.949301 C = Flow velocity coefficient 150 140 130 120 110 H f = (direct from formula above) 21.4468309 24.36660881 27.9471004 33.92234 38.0676 Sika Water level RL M( refer civil dwg) 23.5 23.5 23.5 23.5 23.5 Invert Level of pipe line at KM28, crest RL M 116 116 116 116 116 top of pipe apex(refer civil dwg) 116.8 116.8 116.8 116.8 116.8 static head M 93.3 93.3 93.3 93.3 93.3 Estimated Station loss M 1 1 1 2 1 Velocity head =V^2/2/9.821 M 0.046 0.046 0.046 0.048 0.046 140 45 edegree bend lost M 1.26 1.26 1.36 2.36 1.45 Total system head M 117.053 119.972 123.649 131.627 133.863
SMALLER C VALUE INCREASES H FRICTION SAMALAJU ACTUAL RUN =117M 40 38.06759931 35 33.92234 30 27.9471004 25 24.36660881 20 21.44683091 15 Series1 10 5 0 150 140 130 120 110
NEW DESIGN PIPE LINE PHASE 1 D1 -Main pipe Pipe dia in M M 1.70 1.70 1.70 1.70 L =total pipe length in meter M 75,000.00 75,000.00 75,000.00 75,000.00 Pipe internal cross section Area M2 2.27 2.27 2.27 2.27 Q= Flow rate MLD 125.00 125.00 125.00 125.00 M3/sec 1.45 1.45 1.45 1.45 V=Velocity in pipe M/sec 0.64 0.64 0.64 0.64 C = Flow velocity coefficient 150.00 140.00 130.00 110.00 standard without elbow H f = (direct from formula above) 11.23 12.75 14.63 19.92
NEW DESIGN PIPE LINE PHASE 2 New Pipe line 2 D1 -Main pipe Pipe dia in M M 1.70 1.70 1.70 1.70 L =total pipe length in meter M 75,000.00 75,000.00 75,000.00 75,000.00 Pipe internal cross section Area M2 2.27 2.27 2.27 2.27 Phase 2 Q= Flow rate MLD 250.00 250.00 250.00 250.00 M3/sec 2.89 2.89 2.89 2.89 V=Velocity in pipe M/sec 1.27 1.27 1.27 1.27 C = Flow velocity coefficient 150.00 140.00 130.00 110.00 standard without elbow H f = (direct from formula above) 40.47 45.98 52.73 71.83
SMALLER C VALUE, HIGHER ESTIMATED FRICTION HEAD 80.00 70.00 71.83 60.00 50.00 45.98 52.73 40.00 40.47 Series1 30.00 20.00 10.00-150.00 140.00 130.00 110.00
CASE 2 AVOID SELECT HIGH HEAD PUMP FOR LOW HEAD OPERATION EG: PHASE 1 (Q=50%) AND PHASE 2 (Q=100%) Friction Head of Phase 2 =360% of Phase 1
2. PHASE 1 AND PHASE 2, C=140 FLOW INCREASE DOUBLE, H FRICTION INCREASE 360% Q - 50.00 100.00 125.00 150.00 200.00 250.00 H total - 2.34 8.44 12.75 17.87 30.43 46.00 50.00 45.00 46.00 40.00 35.00 30.00 25.00 20.00 15.00 10.00 5.00-30.43 17.87 12.75 8.44 2.34 - - 50.00 100.00 125.00 150.00 200.00 250.00 Series1
SPECIFIED PUMP HEAD TO MEET PHASE 2, WHEN OPERATING AT PHASE 1 50% FLOW, LOWER HEAD, BIGGER FLOW, TOO HIGH KW, MUCH LOWER PUMP EFFICIENCY, PUMP WILL AT RUN OUT CURVE.
IN ORDER TO OPERATE THE SELECTED PUMP AT EXPECTED DUTY POINT AT PHASE 1 : A. Throttled valve to induce artificial head. The Worst B. Trim impeller. Improve slightly. Not applicable if H1 is substantially LOWER than H2. C. Better solution : Use VFD. ( If reduced running frequency is NOT less than 42 Hz)
D. OTHER GOOD SOLUTION FOR MUCH HIGHER HEAD FOR PHASE 2, Use vertical multi stage centrifugal pump couple to VFD. Size motor, VFD, MCCB, MCC and cable according to Phase 2 requirement. Select multi stage pump to meet Ph 2 duty head, remove nos of impeller to meet phase 1 duty head. VFD to fine tune the actual system head against Estimated system head for Phase 1 and 2 Keep same flow, add head by adding more impeller stages
CASE 3 DO NOT OVER ESTIMATE PUMP HEAD BY 10%, OTHER WISE PUMP OPERATING EFF. SHALL BE MUCH LOWER
CASE 4: ONLY SPECIFY VFD WITH PRE LOADED STANDARD INTELLIGENT PUMP CONTROL LOGIC FOR WATER WORK MULTI PUMP CONTROL
DO NOT RELY ON SOFTWARE PROGRAMMER WHO ONLY USE SIMPLE INDUSTRIAL VFD PLUS PLC,
CASE 5 ADD MONITORING DEVICE IF YOU CAN AFFORD Vibration sensor : Alarm for missed alignment of pump and motor shaft Alarm for Damaged bearing on pump and motor Pre alarm for major failure Bearing temperature RTD : Alarm to change bearing Motor winding Temperature RTD : Prevent motor over heat
CASE 6 HOW TO MINIMIZE MISSED ALIGNMENT Always use leveling nuts to set the right level: Pump base skid pipe support
BASE OF STEEL PIPE SUPPORT MUST BE JACKED UP TO BOTTOM OF PIPE. TO AVOID PIPE BEING BENT BY TIE DOWN.
CASE 7 FOR NEGATIVE PUMP SUCTION, INSTALL FOOT VALVE, OVER HEAD PRIMING TANK, AND INDIVIDUAL SUCTION PIPE. EASY FOR GROUP AUTO CHANGE OVER OF DUTY PUMP.
CASE 8 WHEN PUMP MOTORS ARE DRIVEN BY VFD, Genset size can be smaller Starting current =110% FLA MCCB size can be smaller Cable size can be smaller Power factor is >0.95 Power factor correction capacitor is NOT NEEDED
GENSET SIZING WITH VFD DRIVEN PUMPS 2 x 400kw motor pump on duty with VFD Pump 1 in full load FLA1=660 Amp Pump 2 start Starting Max =110% only for 0.5 second) x660=726 Amp MCC maximum current inrush =660+726=1386 Amp. Gen set KVA needed =1386x415x1.732 /1000x110% =1095KVA.
GENSET SIZING WITH PUMPS OF AUTO TRANSFORMER STARTER 2 x 400kw motor pump on duty with A/T starter Pump 1 in full load FLA1=660 Amp Pump 2 start Starting amp =2.6x FLA (6-8 sec) Current inrush 2 nd pump start =2.6X660=1716 Amp =660+1716=2376 Amp Gen set size KVA=2376x415x1.732/0.7( step load of Genset )/1000 =2439 KVA
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