4F19S20

[macgyver42]

Hi everyone, I have a question about water flow. I have a F&W 4F19S20 19gpm 2hp at a depth of about 360ft 1.25" pvc pipe and pumping into a open 3000gal tank, so not much head pressure. My well is supposed to be a 15GPM well. This pump is over pumpimg the well. Could I use a orifice flow restrictor to solve my issues, or would I be damaging the pump? If I can use an orifice restrictor how do I determine the size of the orifice?
any help would be greatly appreciated.

 

[LittleInch]

In simplistic trends, yes you could use an orifice plate and there are many plate calculation websites available, but I did a quick calc on your data and it looks like your pump has quite a significant inlet head which presumably can vary with rainfall and aquifer level. To go from 19 to 15 gpm will be ok for the pump but just be a bit of a waste of energy, but insignificant in the scheme of things. I would use a simple control or globe valve to regulate your flow which can then be changed if your well water level drops or rises. Try not to go below 50% of max rated flow and you won't do the pump our motor any harm

So long as you can do a simple flow measurement from time to time you should be ok.

My motto: Learn something new every day

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

 

[Artisi]

Why do you say the pump is over-pumping the well, do you have any problems with the pump not delivering flow during a pumping session -- if not then you don't really have any problem. The usual problem with over pumping a well is that the water level in the well drops below or near to the pump inlet and the pump may go-of-prime, ie stop pumping until the water level recovers in the well - the water table draw-down may well be still at a sufficient level not to result in any problem it is just that the well screen has insufficient inflow capacity to keep up with the pumped outflow.

You post doesn't really give enough real info to assist with a pumping problem, that's if one exists anyway, however your question on orifice plate is probably well covered by LittleInch but I would be looking a bit further into the well / pump performance before going the track of controlling the pumping capacity.




It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[macgyver42]

The pump has a steady flow of water for the first 2 minutes or so then it starts surging.Thats why I am assuming that its over pumping the well.

 

[Artisi]

Fair assumption. See LittleInch. However is this a new or an existing well.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[macgyver42]

its a new well. 1 of 3 actually.

 

[macgyver42]

I have thought about trying to use a VFD drive and just regulate the pump that way but the problem is that its a single phase 220v pump. I have found a couple manufacturers of single phase input and output but not very affordable.

 

[Artisi]

forget VFD, just follow what LittleInch set-out, fit a valve in the system somewhere and restrict flow until the well outflow balances the inflow, power wastage will be insignificant, probably even hard to measure it will be so little.
It could be a seasonal thing, although at 360ft I wouldn't expect the aquifer level to fluctuate very much - it could aquifer permeability, well inlet area, or the well hasn't been developed correctly.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[macgyver42]

I will give it a try. Thanks guys I appreciate it.

 

[LittleInch]

Be aware that the 19gpm pump is actually 17gpm @350ft water level with no pressure at the surface. However if you start at say 200ft water level then it pumps at up to 22.5gpm. That pump will go as low as 6 gpm if the well isn't quite as good as you thought and the steady state pumping is less than 15gpm. I would start at 10 and go upwards from there after an hour of steady flow.

Good luck.

My motto: Learn something new every day

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

 

[Artisi]

The problem is really lacking any real technical information and there could be a number of solution's to get you back to a lower flow-rate but you need to give more information. A couple of quick points for starters>

Was the well pump / flow tested at completion, any results?
Has there been any change to the standing water table?
How do you know the pump is delivering 19GPM, has this been measured or is it just an assumption based on pump data, which for some reason uses 19GPM as a reference point?

However get some meaningful advice, I suggest you throttle the discharge flow and accurately measure the output under steady flow conditions, this means a bit of trail and error until the pump can run at maximum output without losing prime (surging) this will allow some "guess work" as to where the pump might be running on its curve - from there we can re-assess what the best move is. If the pump is over capacity, I am thinking maybe long term you could think about removing 1 impeller from the stack but this requires some accurate flow measurements to make this sort of decision.

Alternately, seeing as how this is really only a "toy" pump of 2HP, just throttle the discharge to a point that the pump runs without surging and leave it at that.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[macgyver42]

Artisi, you mean I can disassemble the pump and remove an impeller and reassemble it in the same housing and it will work like normal (with less flow)? Wouldnt the void in the housing be a problem?

 

[Artisi]

macgyver42, I can only answer with an un-qualified yes as I know nothing about theses pumps, their construction and how they are assembled.
I theory any vertical pump can have 1 or more impellers removed to give less head. As for reducing flow, yes it will but flow is a function of the head imposed on the pump and without more detail there is no way to predict the flow rate.

Suggest you ask the manufacturer if 1 impeller can be removed and what is involved, they will probably ask why -- so you need some answers - same as what I have asked so they can advise you on likely flow rate.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)