Pump Type Replacement for Submerged Motor Centrifugal Pump (Sanitary Water Service)

[Tilas]

Hi Guys,

We currently have an existing 30 m3/hr submerged motor centrifugal pump for a water service (Density 1000 kg/m3) with suspended solids 4-5 gram/liter. It was pumping the liquid from the pit to a differential pressure of 0.90 kg/cm2.

Now our Operations people again want's to have the pump changed to an above ground installation which will not give them maintenance problems as the submerged motor centrifugal was giving(the submerged pump has a lifting chain on the top of the sump where it is pulled up during maintenance but the chain got corroded and was broken and now they cannot lift the pump nor they empty the sump because of some restrictions). The suction lift from the bottom of the pit to the ground is approximately 5 meters. We only need manufacturer standard pump for this application as this is just for water treatment process.

With this , could you advise me if which could be of best pump type option to replace the vertical submerged motor pump for this application and what is its merit over the other :

a. Self Priming Centrifugal Pump
b. Vertical Centrifugal Pump (like VS4 motor on the top).
c. Vertical Progressive Cavity Pump (as there are some solid particles 4-5 g/l in the pumped liquid)
c. Any other pump type that you can think of which would work.

Thanks in advance.
Tilas

 

[Tilas]

Hi Guys,

As follow up to the above , I have attached the sketch of options for the pump replacement.

Please give me your thoughts on this , which one is the best replacement type and why.

https://files.engineering.com/getfi...0e7&file=Vertical_Centrifugal_Pump_Option.PNG

https://files.engineering.com/getfi...02fe4&file=Self_Priming_Option_Above_Sump.PNG

https://files.engineering.com/getfi...e&file=Self_Priming_Option_At_Grade_Level.PNG

Thanks in advance,
Tilas

 

[Artisi]

I would opt for the first one, if you can find one suitable for the duty in terms of flow, head, solids handling, and corrosion resistance ( seeing as how the chain on the submersible fell apart).

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.)

 

[LittleInch]

ditto.

The less issue you have with priming the better.

The vertical pump sometimes likes to have a fresh water flush to clean out the bearings and seals rather than the gritty stuff you have.

Beware the length of a prog cavity unit. Most I have seen are 4-5 m long but great pumps for handling sludges, grit etc

On all your options be careful about vortexs at low level sucking in air.

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

 

[Tilas]

Hi Artisi, LittleInch,

In this case I would go with the self priming pump.

However, I might have problems on putting the pump directly on top of the sump due to some space constrains.
I could put the pump on the grade(which is lower than the sump see attached sketch) but I don't know if this sketch will work with the self priming pumps.

Please see attached sketch.

https://files.engineering.com/getfi...9&file=Self_Priming_Option_At_Grade_Level.PNG

Thanks,
Kristian

 

[Artisi]

Really no need for the pump to be self-priming if the discharge point is higher than the top of the tank - the drop leg over the sump and the discharge pipe work will retain sufficient product to keep the pump fully primed. Initial prime and reprime if ever necessary could be via a pipe /valve arrangement from an external water source.

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.)

 

[LittleInch]

I agree,

Especially if you size the down pipe from the top of the tank at say two pipe sizes bigger than the suction lift pipe, you should be able to pull water up the lift pipe providing you can keep the down leg full of water, or provide a water supply to "prime" it.

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

 

[Tilas]

Hi Artisi / LittleInch,

Thank you so much for the recommendations. Noted for the pipe valve arrangement for initial prime and re-prime(as necessary).

And noted also that we don't need to have a self priming pump for this arrangement(only make provisions for initial/re-prime).

Tilas,