iron ductile pipe corrosion

[wildi81]

We have a 4" iron pipe that carries ground water from a submersible pump to the water distribution pipes in our plant.
The first 4" elbow from the pump fails twice a year from corrosion.

The pump runs 24/7.

The ground water is high in iron.

what type of corrosion is occurring? Is this electroysis corroding the pipe?

Will replacing this iron pipe with stainless prevent this?

I will appreciate any comments or suggestions to correct this problem.

Thanks

Tom

 

[rconner]

Was just curious what is the flow rate of your pumping operation? Is it possible the "groundwater" containssand from the ground? Is the holein the el by any chanceon the "outside" of the bend?

 

[wildi81]

Additional info.

The pressure on the line is 80psi.

The wells pump very little to no sand.

The iron content is 2ppm.

Usually the corrosion occurs on the outside radius.

Thanks

Tom

 

[rconner]

If you do not know the flow rate (in e.g. GPM or ft/sec etc.), would it be possible to provide some physical description such as the length of pipe and the discharge condition in the plant so that this could be approximated? In other words where is the 80 psi measured, and is it pushing the flow from the "wells" through a specific length of 4" piping to some open ended discharge or tank etc. in the plant? From your description, unless there is some stray current discarging at this precise location this sounds suspiciously more like wear (for some reason) than "corrosion". While a more detailed water analysis might be a little more enlightening, I cannot imagine 2 ppm iron in water, or for that matter virtually any water, eating holes in an iron fitting in six months! Have the fittings been provided with any sort of lining?
If some mechanism of wear on the back of the ell fitting is however involved, I also am not sure "stainless steel" ell/piping would solve the problem, as I suspect the SS fittings are normally promoted with a thinner wall, and the stainless steel might even be some softer than the ductile iron you have now!
In any case I believe ell fittings or linings where particularly abrasive effects occcur may be available from some sources (and might even be adaptable in some fashion to your set-up), and I have even seen in the past even some quite special elbows with special sort of bolt-on/removable/replaceable wear pads on the outside of the bend where wear occurs in extreme services.