centrifugal pump booster 3

[cb92]

I've worked with pumps for years, and always felt that a lot of electricity was used to get the last 5 pounds of pressure, although not much water was pumped. Has anyone seen a fixed displacement booster running off a bleed line feeding back to the intake? I always liked the old piston pumps. For every revolution, you pumped the same amount of water, they would get the last 5 pounds quickly.

 

[Artisi]

cb92 (Mechanical)
".....and always felt that a lot of electricity was used to get the last 5 pounds of pressure, although not much water was pumped."

This will depend on the pump being used, you cannot blame equipment for faulty selection on your part.

 

[cb92]

Artisi- I'm talking about centrifugal pumps 1/2 to 2 hp, that have a pressure tank. From my experience waiting for one to cycle off so I can check the pressure switch setting, it seems that as these pumps enter the edge of their curve, efficiency drops off. I'm proposing an energy saving device that would improve the curve, similar to the benefit that a shallow well adapter adds to a well pump.

 

[Compositepro]

The shallow well adapter for a centrifugal pump is an ejector that simply allows the pump to operate at a lower suction pressure to draw water to a greater height. It reduces the energy efficiency on the pump. It would be hard to improve on the energy efficiency of the old hand lever pumps which had a piston at the bottom of the well, but I don't think too many people want to go that route.

 

[cb92]

Well said, Compositepro. I guess the shallow well adapter does steal some efficiency from the pump, but it does improve the performance of the pump. What I am discussing is improving the upper end of the pump's performance with an add-on that uses flow from the pump to pump higher pressure. That higher pressure would feed into the outlet line to the pressure tank. Return from the add-on would go to the suction side of the pump.

 

[agmotes]

seems like a splendid idea to me. Centrifugal pumps dont seem very efficient at high head, but are awesome for high flow...as where displacement pumps are awesome for high head, but relativily bad at flow for their size... With this setup it seems like, since ur getting a low flow to begin with due to lost efficiency, the displacement pump would be very beneficial.

agmotes

 

[TheTick]

How about a gear pump? Positive displacement, continuous flow, simple.

 

[EngineerTex]

Using multiple pumps is pretty common in the hydraulic power industry in order to achieve higher overall system efficiency.

I use a lot of diesel-powered hydraulic power units with multiple stacks of positive displacement pumps. The system that you're talking about is a mix of centrifugal and positive displacement, but the theory is the same. At low pressures and high flow rates, I have four pumps running at a total of about 300 gpm at 500 psi. At higher loads, one of the pumps kicks out at about 1000 psi so that all the power from the engine is put into the remaining three pumps. Flow rate is decreased, of course, but this is intuitive -- the system is requiring higher demand because of the higher load, so the system is moving slower. As pressure (and load) becomes greater and greater, additional pumps kick out until only one is left at full 3,000 psi and only 50 gpm. The system is designed so that the pressure-flow curve is matched to the power curve of the engine.*

So, what you're talking about is a tried-and-true means of of matching power to the system and I'd say that you might have an opportunity to save some money.

-T

*As an aside: My power curve could be matched much more closely through the use of variable-displacement pumps, obviously, but since this is mobile equipment that is subject to a ridiculous level of contamination, we don't use VD pumps, since they're much more sensitive to that than gear pumps.





Engineering is not the science behind building things. It is the science behind not building things.

 

[cb92]

I want to thank everyone for their input, it's been very helpful. This is just a theoretical exercise, something I enjoy.
Adding to this Rube Goldberg device, I've been made aware the startup amps of a house pump is the real consumer of electricity. What if the pressure tank were capable of handling higher pressure? A pressure reducing valve could drop pressure down to safe levels for the house. The two-stage pump could put more water into the same size tank. I know a larger tank would be more practical, but sometimes space is limited, and bigger tanks cost more. The net gain from this would be longer pump runs with fewer startups.