Pressure Reduction with the Pump as turbine in drinking water pipeline 1

[hansforum]

Hello,

Local drinking water supply company has problem with high pressure in the pipeline. Reservoir is located 100m above the valley so the pressure inside the pipeline at the bottom is 10 bar and it is supposed to be 4 bar. Average water flow through this main pipe is around 80 l/s. I am thinking about using pump as turbine to reduce some of this pressure, but flow is fluctuating through the day/year so some kind of pressure reducing valve has to be used so that pressure around 4 bar can be achieved in every flow condition. My question is at what elevation this pump as turbine has to be and where pressure reduction valve has to be placed (immediately behind the turbine ?). In that arrangement with pressure reducing valve how do we estimate head for power calculation (neglect pipeline loss)?

Thanks

 

[LittleInch]

Hydro turbine (not a pump) should be at lowest point with valve downstream of turbine with a fixed downstream pressure to maintain. This way if the turbine takes all the 6 bar the control valve will be full open.

If you search on this site for hydro power turbine, you'll find quite a lot of useful info. You would nerd some sort of variable resistance to be able to maintain a fixed speed and frequency but with variable power output. That's the theory anyway...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[JJPellin]

Actually, you can use a standard pump as a turbine. There was a paper presented at the Texas A&M Pump Users Symposium that described how to estimate the performance. You can search their site for the paper. It was probably presented 6 or 7 years ago.

Johnny Pellin

 

[BigInch]

There are inverters/converters now that accept variable frequency input and produce constant frequency and voltage output, as used on newer wind turbines. Kind of a reverse VFD.

http://www.google.ae/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CGoQFjAJ&url=http://

http://www.icrepq.com/PONENCIAS/4.2...9bIJbFRnvuEim7KzDe5b2Kw&bvm=bv.51773540,d.Yms

Independent events are seldomly independent.

 

[JJPellin]

I have attached a link to the paper that I referenced.

Johnny Pellin

 

[ccfowler]

About 30 to 40 years ago (mid-1970's), some pump manufacturers actually published some performance data for some of their pump models when being operated as turbines. I was interested in the possibilities at the time for an odd application that never developed. Some of this information may still be available. If I recall correctly, some of this information was published in their standard catalogs with additional information in supplementary literature. It was part of the energy efficiency and energy recovery excitement of the time.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[DubMac]

ccfowler you are correct sir! Johnston Pump and Byron Jackson both made and sold vertical turbine pumps into the hydroelectric market out West. Herman Greutink of Johnston was a master at designing them; I remember him telling me there was virtually nothing different in designing a VTP as motor as opposed to a pump, which used to puzzle me...

As a result of those companies being "absorbed" by Sulzer and Flowserve respectively, those Engineering files are most likely gone forever; they were all on paper and probably chunked.

 

[BigInch]

Thanks JJ. Don't often see those curves.

Independent events are seldomly independent.

 

[hansforum]

Does anybody know how pressure drop across the turbine changes when the flow is changing? Does it change like the turbine mechanical efficiency? If we have 60m head with the rated flow flowing through the turbine there will be 60m head drop (or 6 bar pressure drop) across turbine or it will be lower? what happens when we have lower flow through the turbine, does head drop across turbine also drops? Turbine speed would be controlled by the grid.

If we have 100m head available how can we use just 60m?