Pump Design In WaterCAD 6.0 4

[prasadvenkat]

Can anybody please,tell me how to design a pump in WaterCAD 6.0.Our project site has 130 ft of elevation difference.

When iam trying to use standard extended method for the pump.It is showing me fields to input shutoff head, design head and discharge, and Max operating head and discharge.What are these fields exactly.

Your help is greatly appreciated.

 

[DMcGrath]

You will have to start by picking a pump and getting the manufacturer's pump curve data. Shutoff head is the head (in ft) where the flow (in GPM) is zero, typically the far left of the pump curve. Design head is the head at which the flow is where you want the pump to operate. Max operating head is the far right (head & flow) of the pump curve. Watercad will use this information to build a pump curve that it will use in its calculations.

 

[francesca]

As DMcGrath said, you have to start with an actual pump. In order to pick your pump(s) from a manufacturer's catelog, you first have to define your flow conditions that you're designing for. That is, the elevation difference, residual pressure required (unless you're pumping to an elevated tank), and the flow rate. The pipe size and material (and age/condition of the pipes) will also affect your head loss during operation.

Build your network in WaterCAD, include appropriate minor losses (bends, Ts, expansions/contractions, etc.) and try out various real pump configurations.

You will probably have to design for some fire flow and the local authority and/or State will have rules for this. You may be required to provide fire flow in addition to normal peak flow, with some residual pressure, at the highest point.

 

[prasadvenkat]

Thank You so much for your help

Mr. McGrath and Mr. Francesca.

How can I find out the design head.My project is a residential custom homes on the hill. We need to feed the water from existing reservoir tank which is appr. 130 ft lower from the highest finish floor using a pump.Minimum pressure required is 45 psi and max is 95 psi.Velocity of the pipes should not exceed 20fps.These are the agency criteria.

Can you suggest any manufacturer manual for this kind of situation.

Thanks

 

[quark]

what criterion sets the limits for maximum and minimum pressures? Is it the varying consumption rate or something else? 130ft of elevation corresponds to 56.35 psi, so your pump discharge pressure should always be higher than this.

Check the average flowrate required (you can find some details on residential consumption from past threads). 20 fps is a high velocity, though not very bad. I would consider not more than 10 fps. Once you fix the pipe size corresponding to the required flowrate and the design velocity, you can check the pressure drop by Darcy's equation or any other formulae comfortable to you.

This software will be of much use to you,

http://www.xs4all.nl/~kostermw/dP/

Add the pressure drop in the pipe to the discharge elevation and you will end up with the head requirement of the pump.

Crane Technical Paper 410 is an excellent reference for pipe sizing calculation.

 

[francesca]

WaterCAD software is adequate for this application. (The original question asked how to do it in WaterCAD.)

The velocity limit will set the pipe size. You need to come up with some demand flows -- fire flow, if required by the agency, and consumption, with appropriate peak factor.

Smith & Loveless is a popular pump manufacturer and their engineers will work with you to check your design.

Really, if you don't know how to design a pump, you should hire an expert. Pump stations are expensive, and purchasing the wrong pump because you made a small error in the calculations (forgetting to add minor losses, using too high of a Hazen-Williams coefficient, etc) will cost far more than the services of an experienced engineer to design the pump.

 

[sokos]

I suggest that you size your pipes based on the design criteria that you are working on. I have noticed that your values are relatively high. Usually we size a pipe for a max. velocity 2.5 to 3m/sec and max headloss gradient 15 to 20 m/km.
then you will get the friction losses. Add the friction loss to the head loss to get the total head. Multiply it by a factor approx 10% to get the design head of the pump.
Having obtained the design head and already you have the flow that the pump has to deliver you have to fill them in WaterCad.
If it is not clear, use the help in WaterCad or have a look on Haestad Book, "Advanced Water Modeling..."