Winston Engineering Case Study 11

Case Study 11

Product: EMV64-60-1FC2370T (2 units)

 Problem: One unit of pump can achieve rated pressure but another unit (same model) cannot achieve!                                                                                        

  

Possible Cause Analysis: 1. Pump not reach rated speed                                 

                                             2. Pump one or two stages impeller missing                                 

                                             3. Wrong direction of rotation                              

                                             4. Pressure gauge not working

Remedy/Recommendations: 

1. One pump is using for water can achieved 13 bar, another pump is for oil only achieved 10.8 Bar

2. The pump for water (S.G.1) can achieved 13 bar (13 bar x 10.2 / SG1) = 132.6m (as per curve) 3. 

3. The pump for oil (S.G.0.83) only achieved 10.8 bar it because of S.G. (Specific Gravity),  
    For Oil actual result: 10.8 bar x 10.2 / SG0.83 = 132.6 m (same as pump curve but take note is only 10.8 bar)     
    During selection of pump curve, must Calculate at 13 bar x 10.2 / SG0.83 = 160 m (as per curve), so that in actual   
    operation can achieved 13 bar. The factory pump curve head is in m, tested with water, SG 1.
    To be understand again, we work back calculation 160m / 10.2 x SG0.83 = 13 bar (For oil)
4. Recommendation: To change the pump, add stages if a multistage or increase the pump speed (with inverter)    
    Customer is installing with inverter so we can suggest increasing the speed and advising as follows:
    RPM required to achieve 160m (S.G.0.83), When Y is RPM. Current pump speed at 50Hz is 2900rpm
    (Y/2900)^2 x 130m = 160m (Affinity Law) Y = 3216 rpm              
    Absorb power @130m (SG1) is 33kw (pump curve), So Power absorb @ 160m (3216 rpm):
    (3200/2900)^3 x 33kw = 44.28kw (Affinity Law) 44.28kw x 0.83 = 36.75kw (Supplied motor is 37kw so is sufficient)

5. you can compare that 10.8 bar (Oil) divide 13 Bar (SG1) = 0.83 (SG)

6. Note: if run at 3216 rpm (37.28kw at SG0.83), the motor power is under size and we limit at 3200 rpm

WINSTON ENGINEERING CORPORATION

1 Joo Koon Way, 628942 Singapore

Our mailing address is: marketing@winstonengineering.com.sg