Newbie with a big problem
Newbie with a big problem
(OP)
Hello all,
Thank you for taking time to help. I am faced with in my mind the impossible. A customer of mine needs me to increase water supply and demand without doing any type of piping. Here is the situation: You have a 10 thousand gallon storage tank with a existing 7.5 hp booster pump trying to feed a total of 1500 fixture units, with a total developed length of approximately 1600 LF of 1 1/2 PVC ran underground. What they are feeding is barns at a race track, and each barn has about 18 hose bib's and a total of four complete bathroom groups. Their reason for doing this is to get off the city water supply and get back on their well supply. I have offered variable speed drives, but my concern is that you can only push so much water through that size of line. I apologize for the stupidity I am spewing out here, but I can't wrap my head around this one. Am I off base by wanting to increase line sizes? Or is there something that could work here? Please help, I am desperate. Thank you in advance again.......
Thank you for taking time to help. I am faced with in my mind the impossible. A customer of mine needs me to increase water supply and demand without doing any type of piping. Here is the situation: You have a 10 thousand gallon storage tank with a existing 7.5 hp booster pump trying to feed a total of 1500 fixture units, with a total developed length of approximately 1600 LF of 1 1/2 PVC ran underground. What they are feeding is barns at a race track, and each barn has about 18 hose bib's and a total of four complete bathroom groups. Their reason for doing this is to get off the city water supply and get back on their well supply. I have offered variable speed drives, but my concern is that you can only push so much water through that size of line. I apologize for the stupidity I am spewing out here, but I can't wrap my head around this one. Am I off base by wanting to increase line sizes? Or is there something that could work here? Please help, I am desperate. Thank you in advance again.......





RE: Newbie with a big problem
RE: Newbie with a big problem
The pipe system needs to be entirely identified.
VFDs can't increase the capacity, without overspeeding the pump you have now. Probably not the best idea to start with.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Newbie with a big problem
How about installing some large expansion tanks in each barn?
RE: Newbie with a big problem
RE: Newbie with a big problem
y is the head required
x is the flow rate
m is the friction loss factor in the sytem
b is the static head
So, you need to solve for m and b to know the curve. "b" is easy. You just figure out the elevation difference between the water level in the suction vessel and where water is discharging (plus the static system pressure if the pipes were discharging into a pressurized vessel). If the suction vessel level is higher than the outlets, this will be a negative number.
"m" can be more tricky. If you know the current flow rate, and the differential pressure of the pump, you can convert the differential pressure to ft of head and solve the equation for "m".
Alternatively, you can measure the length of pipe, count all the elbows and bends (being sure to note what kind of fittings they are) and use a reference like "Crane's Flow of Fluids" to calculate the total friction loss.
When you are done, you will see that the system curve is a parabola.
If you are currently operating where the curve is not yet vertical, a bigger pump will produce more flow. If you are operating where the curve has gone "vertical" you will need a huge pump to produce more flow, and you might create unintended problems like broken pipes. If this is the case, installing larger piping will almost certainly be cheaper than the big pump.
Once you have an idea of what the system curve looks like, your answer should be pretty straight forward. Good luck.
RE: Newbie with a big problem
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Newbie with a big problem
It sounds like you need to feed the existing system from multiple locations. An expansion tank (or a second pump) at the far end of the piping system would feed from both sides, effectively halving the peak flow thru the existing pipe system.
Mtngreen's suggestion of several smaller expansion tanks spread thru the system may be more cost effective way to handle peak flows.
RE: Newbie with a big problem
RE: Newbie with a big problem
Steve
RE: Newbie with a big problem
David
RE: Newbie with a big problem
how about installing low-flow nozzles to reduce consumption?
regardless, good luck!
-pmover
RE: Newbie with a big problem
So the best approach is to have pumps in parallel if possible to gain in flexibilty and all equipped with VFD.
If you succeed to develop enough flow capacity, on the other side probably you will run overdesign of the pipe network size. That means even if your Pipe Nominal Design Pressure cover your duty, at least you will significantly increase losses and system resistance. Then typically you will also need to go with pumps with one size higher.
So in summary, if you have some margin with pipe design pressure, use higher sizer pump, VFD and eventually operates pumps in parallel.
I think there is some tradeoff between changing/improve or adding lines to pipe network (Capex) and keep network while runing with higher losses (Opex)..
Rgds
Wimple
RE: Newbie with a big problem
Sorry, but you've got several problems you're ignoring.
The OP does not want to add pipe.
We already know that the system curve is maxed out, so how will another pump help that situation?
Its not people using water for domestic use; its at a race track, so use is not random.
How do you get more flow with a VFD? Is the VFD needed so you can buy a too big pump, then slow it down?
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Newbie with a big problem
RE: Newbie with a big problem
RE: Newbie with a big problem
The suggestion was to increase flexibility in order to accomodate variable demand/consumption. Maybe I did not get it means the demand is stable?
So if the point is only increase capacity from Flow A to Flow B. Then you could keep same pump size and use VFD (I think appropriate only for moderate increase of flow)
In case jump of flowrate is significant, I suggest to add pump in parallel then either combine with VFD or increase pump size as you need to have a single pump operating at the right of BEP.
In any case, the Pump discharge head will increase.
As there is constraint with pipe size because they dont want to change it, they you check if they have some margin with actual pipe design pressure. I think it is the limiting factor, dont you agree?
Rgds
Wimple
RE: Newbie with a big problem
sorry I meant at the left of the BEP
RE: Newbie with a big problem
RE: Newbie with a big problem
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Newbie with a big problem
RE: Newbie with a big problem
The addition of one or more tanks seems to be the easiest way to handle the periodic higher demand. But, instead of chlorine, UV treatment on the tank(s) fill side would probably be better for the horses and whoever has to maintain the system.