Exploitable??

Waste water pumps are often open impellors to avoid clogging and can be pretty inefficient.

Not much to go here....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Ummmmm.... word usage issue here ?

"Exploitable" can mean "easily fooled" as well as many other things ...

https://www.merriam-webster.com/thesaurus/exploita...

Can you tell us what you are trying to do ??

MJCronin
Sr. Process Engineer

Are you asking why is it 32%?

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.)

Only 27 more questions before we can sort through the broken english to find out the real issue !!!

HUZZA !!!!

MJCronin
Sr. Process Engineer

Submerged wastewater pumps are very inefficent as noted by LI. 32% is on the low side.

Are you talking about a 5 Hp pump or 300 Hp pump? The inefficiency is not a bother on the small pump, but may be an issue with a larger pump.

Hi
It's 40 HP with open impeller to transfer wastewater from a sewage lift station to another (2500 meters).
My question was: Using a pump with 32% efficiency for this operation (Is it the optimum choice ?) if NO, What should I do (Changing pump type ?.....)
Mr. MJCronin : I'm sorry for my broken English.

First you need to create a pump data sheet with required duty point with head and flow and then send it to different pump suppliers.

Then if this duty is continuous or operates a lot then start to look at the efficiency of the pump and calculate the OPEX costs and not look just at the price.

Is your pump operating at its best efficiency point? Is it too big or too small?

Have you got the pump curve? And the process conditions?(flow, head)

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

LittleInch : the pump I talk about is one of the supplier propositions.
I sent him the datasheet with the operating conditions.

yousseff,

You need to put out all the information you have and not just drip feed information. How was I supposed to know that?

Then it's part of your evaluation. Look at power consumed over say a 5 year period and then include the CAPEX cost for different options.

Often a vendor will give you the best choice he has available. Which may not be the best available in the market.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Thank you so much Mr. LittleInch

Hi Youssouf,
I agree with all the comments above. I just want to remind you that you may need a much bigger Capex if you need a spare pump installed to guarantee the operation 24/7.
Make it clear with the operation and maintenance teams.
Normal practice is to get several quotes from different suppliers (at least 2) to make a comparison.
My 2 cents
Pierre

3
Then you can toss the hi and the lo.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

Since this is a wet pit type pump, guess you'll need to take a good look at the shaft seals. What alarms are provided for seal failure?
Also check and compare materials of construction, % excess power available.

As usual too much info way-off from the original question of why low efficiency. Without a lot more detail from the OP it's all wheel spin.

To youssouf, how about posting the data you you sent to the pump supplier so that those of use who know how to select pumps can make some sense of your question.

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.)

georgeverghese : Thank you for giving me this observation about shaft sealing, It's really important.
Artisi : Please find attached the datasheet I sent to the pump supplier.

• https://files.engineering.com/getfile.aspx?folder=4c126bdc-c621-4ebf-bac8-6

Hi Youssouf,
Consider the document attached to support your work.
To me this is a company to consult for your application.
Pierre

• https://files.engineering.com/getfile.aspx?folder=2e03c3be-49d5-43b1-8859-a

Hi pierreick;
Very helpful doc. thank you

youssouf

Without a good search of the internet and not having any pump curves available, I think finding a pump rated at 18m3h @ 79 metre head pumping waste water with a decent efficiency will probably be impossible. As it is pumping waste water it should be running at maximum 4 pole speed - this will mean a large pump running well to the left of the curve at very low efficiency.

Can you post the pump selection you have showing the 32% .

PS. Changed possible to impossible (typo error)

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.)

At the OpCo I used to work at, there were problems with swelling and chemical degradation of the rubber sheath for the water wetted section of the electrical power supply cable - caused by incompatibility of this rubber with traces of petroleum in the caisson. If your waste water is acidic, check this sheath and cable gland materials also.

That sounds like EPDM rubber jacket, typical for SOW cord.

One trick I have learned is to run the cable in a plastic tubing as use compression fittings instead of cable glands. It's much less expensive to by chemical resistance in tubing than in cable. FEP tubing covers a very broad range and works well with compression fittings.