Industrial water intake generalizations
Industrial water intake generalizations
(OP)
I need to determine avg cost for each user for every one foot drop of pool given only normal pool elev., intake elev. and permitted withdrawal amount (and general energy costs) - no pump info, pipe size, or anything about the system above the normal pool. What generalizations can I use, which I will state as given or assumptions, to accomplish this? I also have a few sideline questions, though they are actually a part of this.
1. At what level of water above the intake should I consider cavitation a problem?
2. As pool level falls, the head increases and the pump output decreases. How is this normally handled for minor fluctuations? Can power be increased to compensate?
3. My experience is minimal in this area. Can I just use the given head (normal pool minus intake elev) and given withdrawal amount to determin WHP, then use that constant WHP to determine output changes per foot differences in head?
Any help will be greatly appreciated.
Thanks!
1. At what level of water above the intake should I consider cavitation a problem?
2. As pool level falls, the head increases and the pump output decreases. How is this normally handled for minor fluctuations? Can power be increased to compensate?
3. My experience is minimal in this area. Can I just use the given head (normal pool minus intake elev) and given withdrawal amount to determin WHP, then use that constant WHP to determine output changes per foot differences in head?
Any help will be greatly appreciated.
Thanks!





RE: Industrial water intake generalizations
1. the pump type and installation configuration.
2. pump performance curve
3. the design parameters - static head - total head and flowrate at the design point.
Given this info we could make suggestions on possible cavitation, output in terms of flow at various inlet levels and power requirements.
RE: Industrial water intake generalizations
As the pool level falls, you lose suction pressure and discharge head tends to experience a correspondingly similar loss. If flow reduces, the pump will back up on its curve, thereby reducing flow. Suction pressure (pool level) or pump speed will have to increase to maintain flow. You can do that as long as you don't overspeed or begin to lose suction pressure again. If your pump is constant speed, you have no increase of speed option and will be forced to allow pool level to increase, if it can do so, to regain flowrate.
Look at the pump curve and determine over what flow range it is operating based on the above variation in suction pressure, then look down at the power consumption between the hi and lo flow range. Figure the cost of power at somewhere near the average of the hi and low power consumption rates.
Be sure the intake is below low water level enough such that vortexing is avoided and NPSH is always above what is required.
If you were plowing a field, which would you rather use? Two strong oxen or 1024 chickens?" - Seymour Cray (1925-1996), father of supercomputing
***************
http://virtualpipeline.spaces.live.com/
RE: Industrial water intake generalizations
Thanks!
RE: Industrial water intake generalizations
If you were plowing a field, which would you rather use? Two strong oxen or 1024 chickens?" - Seymour Cray (1925-1996), father of supercomputing
***************
http://virtualpipeline.spaces.live.com/
RE: Industrial water intake generalizations
To establish anything worthwhile - pump curve/s are required and 2 things must be know to approximate power input and change to power input from variable inlet levels.
1. the flow rate/s
2. the head - preferably as - nominal inlet head,static discharge head and friction head at maximum flow rate (32MGD).
With the above data a system curve can be drawn and changes in inlet head and change in friction head for the various intermittent flows and power input can be approximated.
As for NPSH, are the pumps installed with negative or positive inlet head, ie, "suction lift" or "flooded suction" - this also makes a big difference to likely outcomes in terms of NPSH.
I see the problem you are faced with as the same as going into a store to purchase an item, the sales person hands it to you but doesn't know the price - you hand then $100 - how much change do they give?
RE: Industrial water intake generalizations
If you were plowing a field, which would you rather use? Two strong oxen or 1024 chickens?" - Seymour Cray (1925-1996), father of supercomputing
***************
http://virtualpipeline.spaces.live.com/
RE: Industrial water intake generalizations
"The purpose of this work is to provide an economic impact analysis of 'loss of pool level' effects as a justification for maintenance and improvement work on the locks and dam."
Maybe I am way off the mark with this assumption.
RE: Industrial water intake generalizations
Regardless, this is what I have to work with. It's not the kind of engineering we like to do, but it comes close to being appropriate for this small $$ component of the economic impacts I'm looking at. Thanks to both of you for your help.
RE: Industrial water intake generalizations
That should be his limiting factor in my opinion. Put the field and let him chase his pump information for the limiting criteria.
rmw
RE: Industrial water intake generalizations
The following link will put you into Gould pumps who have a range of large vertical and horizontal pumps suitable for these applications - not sure if you can get curves but worth a look.
http://www.gouldspumps.com -
These pumps are from what was Allis Chalmers Custom Pumps - no contact names unfortunately as I have been out of the pump business for quite some time.
Good luck - I think you will need it.