Material choice for water pump impeller

[gmh265]

Hey Guys,

I have been tasked with replacing the damaged impellers of a group of water/slurry pumps that are used in the mining industry. They do see a fair bit of nasty fluids including sea water.

The impellers are currently cast iron, and the failure mode is the impeller blades wear away. I was thinking a replacement of 1020 steel fully machined, however I have little experience in material selection, particularly when it comes to corrosion.

What am I overlooking here?

Stainless is not an option unfortunately.

cheers,

Joel

 

[KENAT]

Why were they cast - is it a shape that will be difficult/costly to machine? (Though with modern multi axis machines that's a less common issue.) Would your volumes now preclude casting as a cost effective solution?

What finish was used originally, and are there any new surface treatments that might be better?

Not quite the same requirement but take a look at thread330-295440 for ideas.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[EdStainless]

Often they use Ni-Resist for cast pump impellers. This is a high Ni cast iron that has very good corrosion resistance and fair wear resistance.

What is the original producer offering you? If they are worn then you can't reverse engineer the blade shape.

Fabricated impellers are usually difficult. Even if you can get the geometry correct they tend to have issues with fatigue at welds.

You should not use a plain steel. If you really want better life then you need to look at alloys like 3CR12 or other straight Cr stainless grades.

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Plymouth Tube

 

[MikeHalloran]

1020 is definitely not the hot setup.

You need to do some industrial archaeology. Dig through the purchase records of the company until you find what material was originally specified for the pumps, and whatever was specified for the previous set of impellers.
You will probably find that the extant impellers are not generic 'cast iron', but a high tech abrasion resistant alloy that costs even more than stainless steel.

Whatever it is, work from there.


Mike Halloran
Pembroke Pines, FL, USA

 

[rmw]

Nagle Pumps had a 28% Chrome hard iron impeller material that they used for slurry and mining pumps. Pretty doggoned tough stuff. I remember one nationally recognized pump repair company at a loss of what to do with it because they had never seen a CI impeller that hard.

rmw

 

[Pumpsonly]

So your pumps see some thing more than just water..
Warman pumps used Ni-hard for their slurry pumps.

 

[strider6]

I agree that carbon steel is not an option and you should go at least to the Ni resist, or improve to higher alloy, but you should define better what you mean with "nasty fluid" if you want to make a good material selection

http://corrosionist.blogspot.com/2010/10/selecting-pump-for-seawater-service.html

hope this help

S

Corrosion Control

 

[clay87]

Erosion or Corrosion is main problem? You could always coat the impellers to improve the life of them.