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Centrifugal Pump Efficient Equipment Operation blog contains power optimization in pumping by following way

Centrifugal Pump Efficient Equipment Operation


1. Pump control by VFD and VSM is always efficient than Discharge control valve.

2. Pumps in Parallel switched to meet demand.

3. On Off control in pumping

4. Flow control valve

5. By Pass control

6. Ensure adequate NPSH of pumping system.

7. Continuous monitoring on pumping.

8. Impeller replacement by smaller or trimming should be placed in the case of discharge valve throttling.

9. For Small loads with high pressure requirement boosted pumps are required.

10. For Heat exchangers Maximize temperature difference so minimize flow requirement. Heat exchanger bypass system should be placed in the case of exceed temperature difference.

11. In continuous system over flow line is connected to step back tanks. Maintain levels around 95% so double pumping avoided.

12. Avoid pumping with free fall effect use siphon effect for beneficial effect.

13. Frequent Inspection and Preventive maintenance.

14. Line sizing of circulation line.

15.  Pump should be operated near BEP : Best Efficiency Operation. 

1. Pump control by VFD and VSM is always efficient than Discharge control valve.

Highlights
  • It is gives lower power consumption.
  • Lower speed creates lower pressure on impeller and other internal parts.
  • Lowering   shaft stress, bearing load, vibration and noise in pumping.
  • Increases pump seal and bearing life.
  • Increasing life of piping and installations, Instruments.
  • Bearing life is inversely proportional to 7th power of speed
Pump discharge valve must be fully open, if pump discharge valve is in partially closed condition [throttled] then lower pump size should be installed Impeller must be trimmed. If possible Variable frequency drive must be installed.

VFD : Variable Frequency Drive is speed adjustment by controlling its Frequency of power.
VSM : Variable Speed Motor has winding function which is operating in 25% 50% 75% and 100% Generally found in Reciprocating Compressor.

Read more :  
VFD : Variable Frequency Drive
VSM : Variable Speed Motor

2. Pumps in Parallel switched to meet demand.

Parallel pumping is efficient in following case

System 1 : High Static Head loss system

System with high static head loss and parallel pumps are installed.
Variation in flow is occur and for limited time flow is higher is required.

Pumps in Parallel switched to meet demand.



Continuous operation will increase energy consumption
 
System 2 : Static head loss + Friction loss system

System curve is not affected when combine loss of Static head loss and Friction head loss.

In combine loss system it will result in Higher head and less flow rate per pump. 

If we double pump in operation will not double the flow.

Static head loss + Friction loss system



It is possible to operate Small pump with bigger pump but the condition is they have same Discharge pressure and Head.

3. On Off control in pumping

On Off control should be installed in following systems

A. Continuous fluid dosing system.

If there is a system which has pressure is equal to atmospheric pressure and fluids are dosing with dosing pump.

Dosing pump is not required in this system.

For this type of system Elevated tanks [ Head Tank ]  is best option. From this tank dosing is energy free operation.

Pumping is only required when head tank level is low.

Pumping cost and pump maintenance cost is prevented by this system

B. Batch Processes

For any batch process where fluid required for certain time On Off control must be placed.

4. Flow control valve

This is system in which pump running continuously and discharge flow is controlled by FCV - Flow Control Valve.

Here we are considering 2 systems.

Flow control valve


Flow 1 System : Discharge valve is fully open.

When Flow 1 system is there efficient operation is there. 

Flow 2 System : Partially Close valve.

When less flow required Flow 2 system will be placed. 

It increases additional pressure drop in system.

To over come this pressure drop energy is wasted but still minor reduction in energy consumption.

Losses: 

1. Pump Efficiency loss Power is consumed is almost there and discharge flow is reduced

2. Maintenance cost of pump and lines in between pump and discharge valve increases.

3. Initial installation cost of FCV its maintenance cost and its replacement cost is still there.

5. By Pass control

In pumping system permanent line is placed which returns fluid flow to its suction source.

By pass line is provided for safety of pump and line in case of sudden shut discharge flow.

This system is less energy efficient than FCV installation because pumping fluid is same. [FCV Installation is even some energy reducing]

6. Ensure adequate NPSH of pumping system.

Suction available is more then than required.

NPSHA > NPSHR

Head is proportional to square of NPSHR.

H ∝ NPSHR²

7. Continuous monitoring on pumping.

Install Local Pressure Gauges, Flow meters, and 

Install Instrumentation for pump Monitoring

Pressure Transmitter

Flow Transmitters

Radial Displacement and Axial Transmitter, 

Winding temperature Transmitters

A meter for Current Monitoring

Flow Circulation Control valves

Seal water Pressure switch and Flow Switch

8. Impeller replacement by smaller or trimming should be placed in the case of discharge valve throttling.

9. For Small loads with high pressure requirement boosted pumps are required.

10. For Heat exchangers Maximize temperature difference so minimize flow requirement. Heat exchanger bypass system should be placed in the case of exceed temperature difference.

11. In continuous system over flow line is connected to step back tanks. Maintain levels around 95% so double pumping avoided.

12. Avoid pumping with free fall effect use siphon effect for beneficial effect.

Free fall return in pumping

Free fall return

It pushes liquid in opposite direction and more efforts should be taken by pump

It increases power consumption

Siphon effect benefecial due to it sucks liquid
Siphon effect

Siphon effect beneficial due to it sucks liquid.

Sucking liquid will reduce load on pump and reduces power consumption.

13.  Frequent Inspection and Preventive maintenance.

Here is some check points
  1. Oil level in Oil seal indicator.
  2. Vibration.
  3. Abnormal sound.
  4. Alignment.
Preventive maintenance will reduce breakdowns and loss of any part of pump.

14. Line sizing of circulation line.

If Pump circulation line is over sized and valve is fully or partially opened then Small line or orific should be installed, Pump replacement, Impeller replacement or trimming, VFD installation, Multiple speed motor installation should be done.

15.  Pump should be operated near BEP : Best Efficiency Operation. 

If pump operate far away from BEP it will increase maintenance cost.

Overview


Efficient pumping operation

Thanks for reading -  Centrifugal Pump Efficient Equipment Operation
Naitik Patel
Industrial Guide

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