Anode on only one pump is corroding

[engineer49]

I have a condition with vertical turbine pumps in a wetwell pumping chlorinated water. Chlorine residual is 3-5 mg/L. TDS is about 1200 mg/L. All the pumps are fitted with anodes on the pump column. The anodes on the jockey pump (1 of 4) shows extensive corrosion on anode(fully crusted over). Anodes on other pumps show only minor corrosion. The pump with the corroded anodes has significantly more run time than the other pumps. The pump columns and bowls on all the pumps look to be in excellent condition so there is no concern at this time about pump corrosion. We just don't know why these anodes corrode more than the other anodes. What would cause the anodes on the jockey pump to corrode more than the other pumps?

 

[strider6]

i think that you have the answer. where the pump run there is more corrosion due to the high flow of water vs the optehr pumps where the water is stagnant.. if you have a flowing water there is more oxygen trasnsport and higher corrosion rate.

S

Corrosion Prevention & Corrosion Control

 

[engineer49]

Thanks. We've thought of that, however, in an adjacent wetwell we have some pumps that run constantly and the anodes show no corrosion (same water).

 

[EdStainless]

but are your constant run pump identical to the one with anode corrosion? It still my be seeing higher local velocity.

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Plymouth Tube

 

[MikeMet]

You also need to look at stray electrial current. Sometimes they can induce high corrosion rates in equipment and you anode may be corroding in response.

 

[SJones]

Are all of the anode materials identical?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[engineer49]

The anodes appear to be all the same (same supplier). However, the jockey pump was supplied at a different time than the other pumps.

 

[EdStainless]

One anode is covered with a crust? Does it have greater weight loss? It may be that it is NOT corroding. Normally as they are consumed the surface stays fairly clean.
It may be that this one is not connected properly and it is not working.
Take a good look and see if the crust is anode corrosion product or not.

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Plymouth Tube

 

[engineer49]

It may be that case that we have an encrustation on this anode rather than corrosion. We haven't verified the weight but dimensionally the anodes are the same after we scrape away the crust.