Pump Designing

Hello Michael,

Are all these pumps part of one pump station? 

You can model these pumps in parallel, where downstream pipes of pumps are meeting at one junction and pumps are part of one pump station. 

If pumps are not parallel as shown above, then please elaborate the pump situations further or provide a sketch if possible, 

Hello Michael,

It would help if you provided a schematic of the system you are proposing. Maybe share a snapshot of the model?

Each pump / pump station which is delivering to the common node should be modeled as per the demand and head requirements.

Also, this depends on your operation as well. Are the pumps running simultaneously or are pumping at different times? As my colleague Sushma suggested, are the pumps setup in parallel?

Some addition information about what you are trying to achieve would help.

This is what you wanted in a schematic plan, not actually. All pumps pump water from reservoir at suction side and transfer to 'Final Res' reservoir. I want to know how can select (design) pumps in this complicated plan. I need the method of doing that, not designing these pumps actually one by one.

This is only a sample and I want to learn how to calculate Head of each pump to select good pump.

Hello Michael,

 Pump head selection depends on static head and frictional head. Static head is level difference between pump suction point to pump delivery point. In your case difference of elevation of reservoir on suction side to the reservoir on discharge side of pump. Generally, 10% frictional losses are considered while designing the pump.

And design discharge of pump is the amount of water you want to be lifted from one reservoir to another reservoir.

There is tool is WaterGEMS which will help you with pump selection process, which is System head curve. Based on system it will give you required pump head.

Please go through below mentioned wiki’s which talk about pump selection process and detailed note on how to use system head curves respectively.

General Pump Selection Process 

Understanding System Head Curves in WaterGEMS, WaterCAD, and SewerCAD 

Estimating a pump curve for a model 

This looks like a system with a single pressure zone with multiple sources and a single tank. I’ll assume that this is a water supply system (either domestic or irrigation) as opposed to a pressurized sewer system/force main.

The pumps need to work efficiently over a wide range of conditions

Peak hour vs. Average hour vs./ Minimum hour

Whether one pump running will meet demands vs. Multiple pumps will always need to be running

Constant speed pumps vs. Variable speed pumps

Flat or steep system head curves

Is most of the demand between the pumps and the final tank or beyond the tank

You need to consider various pump combinations. There are two approaches

1. Set up one scenario for each pump combination
2. Set up an EPS run where each time step a different combination of pumps is running

Generate system head curves for each combination.

Right click on pump and look at the graphs to see efficiency.

Run the scenario energy cost tool and look at efficiency for various combinations ($/MG pumped is usually a good indicator).

If most of the energy goes into lift (felt system head curves) then the pumps won’t be as likely to fight with one another. If the energy goes into overcoming friction in a small pipeline, then combinations that work well together will need to be identified and others should be avoided.

Once you’ve picked pumps that meet your needs, run some low, average and high days to see how things will work. You should treat the final tank as a tank rather than a reservoir for these runs. You’ll want to determine how the tank level will fluctuate and how to set up controls.

One trick that can get you started if you know the flow you want for each source: In a copy of the model, replace the pump and suction tank with a negative demand equal to the flow you want. This will give you the HGL needed at the discharge side of each pump.