×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Water Well Impeller Damage

Water Well Impeller Damage

Water Well Impeller Damage

(OP)
Anyone out there hear of damage to bronze impellers in water wells due to chlorinated pre-lube water? Or leaking check valves allowing chlorinated distribution water to enter the well and corrode the impeller?

RE: Water Well Impeller Damage

Not familiar with that, but high levels of dissolved salts will do the same thing.

RE: Water Well Impeller Damage

Yes, but it depends on the the composition of the bronze and the chlorine residual in the water.  The manufacturer would need to give the composition of the bronze and recommended limits of chlorine.

RE: Water Well Impeller Damage

bronzes are used in seawater service. It would be necessary to define exactly the type of bronze  and the type of corrosion. It could be also an erosion related mechanisms. I suggest u to make a Failure Analysis to defnie exactly the causes of the damage

Copper alloys corrosion

S.

 

Metal Corrosion
 

RE: Water Well Impeller Damage

What you are referring to is de-zincification.  Many pump manufacturers changed the makeup of their bronze due to lead regulations.  The lead content was eliminated and a higher zinc content was used.

Chlorine will attack and dissolve the zinc thereby pitting and eroding the bronze impeller.

I've not seen it on raw water well impellers; but, I have seen it numerous times on high service pump impellers and also on solenoid valves for chemical feed piping.  The chlorine levels don't have to be that high depending on the TDS content of the water.

I've made recommendations to several clients and changed my specifications to include cast iron impellers where I think this could be a problem.  Some manufacturers have different bronze alloys for this reason as well; but, it isn't always easy to find in their literature.

RE: Water Well Impeller Damage

I think that Semo is correct.  I've seen the same thing in well pumps.  It dons't much and if the prelube leaks or the check leaks your replacing inpellors and bearings.  I know that you can specify leaded bronze for some manufactuer, but you have to special order.

RE: Water Well Impeller Damage

Cannot see that the minute amount of water from the prelube is in any way the cause of what will be de-zincification of your bronze? impellers, it could well be your second thought of leakage from the distribution system - but even this is a long shot,how much is leaking back and surely it will be diluted by the standing water in the well.

I would suggest getting an analysis of the ground water you are pumping.

RE: Water Well Impeller Damage


 There are impellers available for use where the liquid medium has harsh effects on the normal bronze alloys. They are made of a composite fibre material and are resistant to the usual scouring and cavitation. I do not have the info to hand but an internet search should produce a result.

Offshore Engineering&Design

RE: Water Well Impeller Damage

Cannot see how a composite material is able to withstand the destructive energy of cavitation when even 28% chrome iron with a hardness of 700+ BH cannot. If you are discussing erosion corrosion when this is a different matter altogether.

RE: Water Well Impeller Damage

Are you sure that the well(s) have not ben disinfected by shock chlorination/slug dosing ?

 

RE: Water Well Impeller Damage

De-zincification of the impellers is common in well pumps. It has more to do with the salinity of the water than with corrosion. The well drillers around here use the same metal and get 7-10 years of service life out of the impeller. It is not economically justified to spend more for the impeller.

RE: Water Well Impeller Damage

De-zincification actually only occurs with Brass, not Bronze. Bronze metal does not include zinc in the alloy.

Graphitization is a process where iron leaches from cast iron and weakening the cast iron.

  http://www.hghouston.com/coppers/brass75.htm

Bronze is an alloy of copper, tin, zinc, phosphorus, and sometimes small amounts of other elements. Bronzes are harder than brasses. Brass is an alloy having copper (55%–90%) and zinc (10%–45%) as its essential components. The properties of brass vary with the proportion of copper and zinc and with the addition of small amounts of other elements, such as aluminum, lead, tin, or nickel.

In talking to a well driller today, it is more common to experience corrosion of the stainless shaft of the well pump rather than with the bronze impeller. This would be pitting of the stainless steel.

Wells are annually disinfected for a period of 8-24 hours with a solution of 200 to 400 mg/l of chlorine. Again, this is just one time per year disinfection. After 7-8 years of annual disinfections, there will be evidence of corrosion on the pump shaft, not the bronze impeller.

The chlorination of the water supply would consist of approximately 2 mg/l of chlorine and it would be difficult to see how this would affect the bronze when the 200-400 mg/l of chlorine does not corrode the bronze.


 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources