Stainless Steel and Bronze impellers
Stainless Steel and Bronze impellers
(OP)
Hello everybody:
In the Technical Specifications for the Drainage System of a small hydroelectric plant, it can be read:
“In the case of submersible pumps, the pump and motor shall be contained in the same enclosure and designed as a package, with built suction filter. For over 30 kW pumps, impeller shall be of stainless steel. For less than 30 kW pump impeller may be bronze”.
According to these Specifications, the material change of impellers can be done if there is a change in motor power (depending on the head and flow, which are causing a shift in power), but how is justified the change of material of the pump impeller if the wastewater being pumped remains the same?
Thanks in advance for your comments about this subject.
In the Technical Specifications for the Drainage System of a small hydroelectric plant, it can be read:
“In the case of submersible pumps, the pump and motor shall be contained in the same enclosure and designed as a package, with built suction filter. For over 30 kW pumps, impeller shall be of stainless steel. For less than 30 kW pump impeller may be bronze”.
According to these Specifications, the material change of impellers can be done if there is a change in motor power (depending on the head and flow, which are causing a shift in power), but how is justified the change of material of the pump impeller if the wastewater being pumped remains the same?
Thanks in advance for your comments about this subject.
El que no puede andar, se sienta.





RE: Stainless Steel and Bronze impellers
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.)
RE: Stainless Steel and Bronze impellers
Then generations of engineers in that consulting firm just copied/pasted the spec without ever thinking about it.
Probably the same reason why VFD pumps still get specified with balancing valve..... old habits die slow.
RE: Stainless Steel and Bronze impellers
All younger engineers should be encouraged to query the reasons for ANYTHING before being allowed to use cut and paste
RE: Stainless Steel and Bronze impellers
I am not saying that this is the explanation to the OP problem. But Impeller material, in my experience, is not defined strictly according to the result of the water / pumped medium analysis but also is a parameter to play with to set the total NPSH_required.
RE: Stainless Steel and Bronze impellers
Ted
RE: Stainless Steel and Bronze impellers
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.)
RE: Stainless Steel and Bronze impellers
Independent events are seldomly independent.
RE: Stainless Steel and Bronze impellers
Point is that an increase of temperature of the medium is in general not wanted from a material corrosion point of view.
This is speculative but a food for thought...
RE: Stainless Steel and Bronze impellers
but I don't think whne there is flow (even a little) this is an issue. Especially not with most likley cold wastewater.
you could do the math at what flowrate the pump would even measurably heat up the water. I really doubt this is an issue. If you have 1000 gpm pumps, and only run 1 gpm, thsi might be a problem.
thsi is even less a problem in variable speed pumps, since less rpm mean also less heat.
unless you run 200°F boiler water, i don't see a concern.
RE: Stainless Steel and Bronze impellers
I am very grateful for your points of view and your comments. Thanks.
El que no puede andar, se sienta.
RE: Stainless Steel and Bronze impellers