Pumping hard water 1

[rcooper]

We have a 160kW pump which is pumping very hard water. It has seized twice, and on inspection it was found to have build up of lime scale. The only part of the pump where there are close enough static/rotating components is between the wear ring and the impeller. This is a high efficiency pump designed for clean water so the clearance is very small.

Can lime scale build up on a pump sufficient to stop it from starting or should we be looking else where.

 

[Artisi]

simple answer is yes - lime can build upto such a point that it will cause interference with close tolerances - and is most cases with wide tolerances overtime.

 

[cvg]

yes, hard water can damage all components of the system. We are facing similar situation where depth to groundwater is approximately 4,000 feet. Even if we could afford to drill a $2 million dollar production well, the water quality is so low that it corrodes everything.

 

[arguellesmanuel]

Not only the hard water can bring any problem in the impeller...silice too..!! the temperature have a importan factor...
what is the amount of silice that you have.??

use a bypass use a softener.. o use a dispersant in a cocentration of 10-15 ppm. (poliacrilate or poliacrilamide)


Chem. Tech. Manuel Arguelles
Quality Analist
Venezuela

 

[Artisi]

What temperature is the pumped liquor.

Rubber lined pump have been used as an alternative where there has been a problem of lime build-up - the thinking is that because the rubber is flexible it is probably "fretting" while the pump is running and therefore the lime cannot adhere to the rubber.

Sorry I can't give you any direct reference to this however you might be able to get some info' from one of the major slurry pump manufacturers.

 

[techie5455]

Have you explored electronic scale control systems? Some of the products are not effective and the distributors don’t always know how to implement it correctly so the industry has a bad rap. However, I’ve come across a few solid companies who stand behind their product. I think it’s worth exploring.

Regards,

Doug J. Edwards

 

[bimr]

techie5455,

The "bad rap" will be to your reputation after installing one of these gadgets and then seeing your equipment ruined because of it.

Not one of the gadget makers offers consequential damages for good reason. Money back promises on water treatment gadgets are worth just a pittance while the consequential damages of destroying your facility will be a small fortune.

Here is a bad rap on the gadgets:

http://www.wbdg.org/ccb/ARMYCOE/PWTB/pwtb_420_49_34.pdf

 

[rcooper]

Thanks for all the replies. The water is ground water pumped from a bore hole in a chalk aquifer and then boosted by the problematic pumps.

Coming to this job from a soft water area, I have not come across major scaling before. I knew it fouled pipes but didn't know it could bring large pumps to a stop. Our process engineers are looking at how to soften the water.

 

[bimr]

From your answer, it appears that you have a well pump operating with no problems and a booster pump that is problematic.

If that is true, then you are probably releasing the pressure on the well water, allowing the natural CO2 to be released, which is then causing the water pH to increase.

The least expensive solution is probably to add acid to lower the pH. Lowering the pH will reduce the scaling tendency of the water. To find the best pH, one would use the langelier's index calculation.

The best water treatment solution would depend on the intended use for the water. And you have not said what you are using the water for. A complete water analysis would also be helpful.

 

[rcooper]

We are bringing the pressure down to atmospheric at the top of the well, before re-pumping it. This is for historical reasons. The water is potable water and goes into the local distribution network. I'll have a look at the langelier's index calculation.

 

[techie5455]

I forwarded your comments to a company that I know and I’d like to share their reaction:

Bimr, You sound like you are involved in the chemical industry. I assume this because in our experience, only a reactionary against non-chemical treatment would make the comment you did.

While it’s true that many products do not work well and many of the ones that do work are often not applied properly (which explains the results found in that report you linked) there are definitely companies who have a good product and know how to use it.

There are many studies which prove this:

http://www.trentatron.com/Adobe/heatexchanger.pdf

http://www.conservationsolutions.com/pdfs/studies/f_biological_control.pdf

http://www.cuwcc.org/uploads/tech_docs/PBMP_Report_Year_2_Ind_Cooling_Systems_2006.pdf

and there are many more.

We are also just successfully concluding a pilot with the Navy. We’ll share the results when we can.

But that is all beside the point.

Rcooper has a lime scale problem. How can placing an electronic device on his system, in an attempt to descale it, ruin his equipment? The only way this could happen is if he stopped a chemical treatment program currently in place. So, the way around this is to… NOT TO STOP THE CHEMICALS. If you don’t stop the chemicals, then you risk nothing. Unless you are afraid to see a non-chemical product work. So…

For the benefit of the members of this forum, we’d like to offer rcooper a FREE demo of out product. Don’t discontinue chemical treatment and risk your equipment. Simply allow us to install our device and see if it solves your scale problem…

And then we can publish the results and let the forum members judge for themselves…

Rcooper, please let me know if you are interested.

 

[aquaseaulutions]

Instead of non-proven electronic device, I suggest Filtersorb SP. It is an efficient no salt system than can remove hardness EFFECT. See that article for another similar product. Those products have been validated by well recognized organizations.