Re : Load distribution between duty and assist pumps

Pumps will find their own distribution level based on the system curve and the individual pump curve. Identical pumps will share 50-50 unless unequal restrictions exist.

Thank you Mr.Hendrik for your reply.

Sorry for the delay due to internet connection problems.

Actually i want to design a pump station of 150 lps capacity @ 70 m head. In this case how many duty assist and standby pumps will be required? what should be their capacity?.

Your situation and requirements would dictate your best configuration. Because your situation is not known this comments is only general.

It is usually better to use only one pump at a time. a bigger pump will be more efficient than 2 smaller ones. At 150 lps it might not be that critical.

If the required discharge volume however changes over time 2 or more different or equal size pumps may be the better option.

On irrigation projects with a fixed duty point we often uses only one pump but will keep the necessary spares in stock. The pump can usually be repaired on site in a few hours.

Sharing the duty between 2 or more pumps is good but it may also mean that the pumps may need repairs at the same time.

Pumping really abrasive water (where the pump may wear out in weeks) or where continues operation is critical may warrant the use of at least 3 pumps of which one should always be in new condition.

If you care to give more detail better advice may come your way.

Agreed and GA,

For these low capacity, better to pump with a single one , use the other of same capacity as standby depend on the criticality and MTBF (mean time bet failure) which will be dictated by oper. cond.

Normally in our applications (a bil on lower side) we have the standby pumps automatically turned on as the first pump is switched off (or the pressure/flow on the pump#1 reaches below a set value) the system logic takes care of this, and the pump failed is isolated and replaced (a spare pump is kept in case,) so the unit is never on a down mode.

The efficiency and other charact of a single pump is better than multiple pumps, except in some cases (they do exist under some load patterns) but that is outside this syllabus)

Thank you Mr.Hendrik for your valuable inputs and Mr.sb for assuring it.

Actually it is an irrigation application where the demand is expected to vary over a period of time. So i think i can go for 3 duty and 1 assist of 50 lps capacity @ 75m head.

I am pumping from areservoir of 2 MillionUSGallon reservoir.

I would like to go for horizondal End Suction pumps for 3 duty and 1 asst. Also i will need to place automatic irrigation filter of capacity 250 lps(with automatic backflushing based on differntial pressure).

Apart from this, i understand that we need to provide pressure switch,pressure gauges,Electro Magnetic Flowmeter,Suction Header,Discharge Header,Ultrosonic level sensor,PLC,Irrigation Controller,Pressure Release valves etc.

Now i would like to know

1.How many pipelines(of what size) we need to takeup from the reservoir to Suction Header? How to size suctionlines and suction header?.

2.How to size the delivery header?.

3.I understood that Spring loaded Presure relief valve to be placed on the return line from discharge header to reservoir. But what is the criteria to size this line and PRV?.

4.How all these components are controlled from PLC and irrigation controller?.

Thanks.

Hi I usually leave the suction line for last because the NPSH Req is only known when the pumps has been chosen.

What type of irrigation system are you going for?

What is the area? and what crop? What is the climate like? (partly curiosity)

A good policy on the discharge pipes is to (divide and rule) that is the pipes must go into different directions as often as possible.

With 2 x 85ha centre pivots (rough guess) the pipe could split to feed the individual circles.

With micro irrigation (drip) the blocks operating at any stage could be scattered all over the show.

Maybe I should stop here and wait for more info.

Sorry for the delay Mr.Hendrik(As i was on a weekend trip, Here in United Arab Emirates we have week ends on Friday and Saturday).

We provide irrigation for landscaped areas consisting of Groundcover and Seasonal flowers(irrigated by Drip irrigation),Turf area(irrigated by sprayer and sprinkler) and trees and shrubs(irrigated by bubbler).

Climate : Arid and dry

Soil : Light soil

The irrigation water demand is expected to vary.

If you need any other information i am ready to provide.

Thanks,

Hi techfutura

You need slightly more info than a post.

Have a look at http://gwis.co.za and choose the link to the software. (I think that would be the answer to your question). Maybe even apply for a demo version. Also look at the other link.

Let me know what you think.

Hello Mr.Hendrik,

I have gone through the site and gone through the tutorial. I was trying to get the software online but i could not able to get it through mail. So i have mailed to the administrator asking for the demo version.

I understood that the software is for analysing the irrigation network including booster pumps. But it doesn't give an idea about what kind of instruments and controls we have to use,where to use, how to size them.

Do you know some websites which gives a basic idea about this area?.

Thanks,

The system incorporate all the controls needed.

New / different stuff may be added if viable. (just contact Jacques with a request and some information).

Enjoy!!!!

Thank you Mr.Hendrik for your suggestions.