Submersible pump design dilemma

[Wattmiser]

New to your forums: I recently had a water pumping project thrown in my lap and had my options narrowed down until I read a few posts on the use of VFD's to run submersible pumps,since hind sights usually 20/20 I thought some insight might help.
My project involves pumping water 1,000' with a 40' rise in elevation. My customers irrigation and outside demand is 20-40gpm at a pressure range of 30-40psi. I had originally planned on installing a 5hp 230v 3phase 32stage pump and control it with a 10hp VFD,expansion tank, and a pressure transducer.I think an "on demand" type system would fit there needs but my top priority has to be longevity. My gut feeling says to operate pump with a mag starter and size pressure tanks to benefit the pump. I have one other choice and could just pump to an existing well casing for storage and use a second pump to provide the volume and pressure needed. I will appreciate any and all pointers.

 

[djs]

Perhaps not an efficient system, but you can use a pressure regulating valve at the wellhead which will get your 30-40 psi. Have to have a pump shutdown when demand goes too low.

 

[itsmoked]

Welcome Wattmiser. This forum is for people designing circuit boards so you picked a poor one for your question.
forum237
or
forum248
would've been the normal places.


What you describe can work fine if you're trying to avoid large tanks. Usually large tanks are a fire fighting requirement so they're always present and used, so the pump is fine with standard off/on controls. Large tanks also mean you have reasonable time to service the well/well-equipment when it's needed.
With a storage tank VFD pressure control is an excellent solution for supplying water to the user. There are numerous completely assembled packages available on the market for that. It eliminates all the stoopid water logged pressure tanks and the short cycling they cause the pump before someone notices.


A little concern about your 1000 feet. It's better to have short wire runs between the VFD and the pump or alternatively really long ones. In between usually requires some extra filtering between the VFD and the pump to prevent large electrical standing waves from possibly harming the motor.

Also if the power source is a thousand feet away you have much larger issues to deal with.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

You can use a VFD just fine. If you really want to protect the motor then use a sinewave type filter between the VFD and the pump.

I'm not a pump guy, but you can pick a pump with the right curve and get reasonable efficiency by using a pressure control valve on the output of the pump. The valve basically chokes the pump output off to maintain the pressure. You then need some kind of control that stops the pump under a certain demand. If this is for irrigation you might be able to trigger the pump off of the zone controls that operate the irrigation.

The starting and stopping based on flow is required for a VFD so this part is really no different. The only time the VFD can be simpler is when the VFD has the ability to start and stop itself as part of the internal PID pressure control system.

 

[lukin1977]

There is also a Pump Engineering forum 407