Centrifugal pump and hard water

[Aqua_man]

Hello everyone, I'm new here so please pardon any errors I make for now.

The problem that we're having is scale buildup inside our water booster pumps as well as ending up in our end product;
Water gets pumped from a well into a 6000 gallon storage tank. From there it goes through a primary 2" centrifugal pump plus a secondary booster pump farther down the line. After that the water gets injected with Anhydrous Ammonia, goes through a cooler, than out to storage. The primary pump gets scale buildup and needs tore down and dipped in acid every few weeks, the secondary pump also needs this treatment about every month. Our end product also has evidence of scale/calcium and causes problems in our site tubes. Looking for any possible solutions!

Also, its important to note that we don't have problems with scale buildup in any other water processes we have that are pumped from the well. It seems that we only get scale buildup after the water runs through a centrifugal pump. Any ideas there?

Thanks in advance!

 

[pennpiper]

Have you considered changing the process sequence by adding a mixer to the 6000 gallon tank and introduce the Anhydrous Ammonia in that Tank?

Sometimes its possible to do all the right things and still get bad results

 

[Aqua_man]

Thanks for the reply. But ammonia and water make a violent reaction, so that process must be done inside a special chamber in a converter/cooler unit. The pumps are used to push water in and through the converter and back out into storage tanks.

 

[itsmoked]

Please post the results of the chemical analysis of the water running thru the pumps.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[bimr]

Install a water softener.

I expect that the well water contains carbon dioxide. The carbon dioxide is released to the atmosphere in the 6,000 gallon tank. The release of the carbon dioxide in turn, causes the pH of the well water to increase. Higher pH is associated with scale forming.

 

[georgeverghese]

Sketch of this system, which also shows feeds to these other pumps which dont scale up will help.

 

[ashtree]

Ammonia injection systems can have problems with the formation of Calcium and Magnesium scale in hard water , particularly when injecting into a carrier water line. If using carrier water such water should be softened to bel0w 30-35mg/l as CaCO3. This is a common problem when doing chloramation using anhydrous ammonia.

Probably you will need to set up a softened carrier water line to inject into rather than directly into the pump feed.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[EdStainless]

Either lower the hardness or lower the pH by acid injection.
Loss of CO2 will increase pH and a little bit of heating in the pump will combine to push you into scale formation conditions.

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P.E. Metallurgy, Plymouth Tube

 

[georgeverghese]

From your description, there is no explanation why this centrifugal, which is upstream of the NH3 injection point, scales up while the others taking feed from this same well dont - there is something you havent told us. Could it be that the other pumps take feed straight from the well (without this intermediate low pressure tank where the the HCO3⁼/CO3⁼ balance is shifted)?

 

[SandCounter]

OK, here is an "out there" thought. . .

Factors that encourage precipitation of solids from a solution include surface area on which to nucleate and reduced temperature. So here are some things I would consider. Presumably your pump's ratio of wetted area to volume is higher than the tank. Possibly the water source is warmer and the water is cooling below the super-saturated temperature somewhere between the tank and the pump, encouraging the calcium to precipitate out.

Going on this theory, perhaps insert some sort of high-surface area medium into the tank to attract solids precipitation before it arrives at the pump and cool the tank to encourage the scale to drop out of the water. Maybe heat the water on the way to the pump.

Finally, is your pump cavitating? The instantaneous vaporization of water may cause the solute to drop out.

I used to count sand. Now I don't count at all.

 

[bimr]

Seems the poster is long gone.

The poster does not appear to be having an issue with the well pump scaling up. If that is true, then it is should be obvious that the well water is losing dissolved CO₂ to the atmosphere while the water is in the tank. Loss of the dissolved CO₂ will increase the pH of the well water and increasing the tendency of the well water to scale.

 

[Aqua_man]

Sorry it's taken me so long to get back, work has been crazy.

Thank you everyone for the replies, they have helped a lot. The diagram that BIMR posted is spot on. The 2" centrifugal pump and the secondary pump are scaling up, while other pumps that are fed directly by the well pump before the 6000 gallon tank do not scale up.

It seems the solution would be to soften the water? If we put a water softener between the well pump and the 6000 gallon water tank will that solve our problem? Or do the centrifugal pumps have anything to do with breaking the calcium out of the water?

 

[bimr]

You need a water softener. Don't worry about the pump.

 

[Aqua_man]

Great! Thank you very much for the confirmation.

 

[georgeverghese]

Agreed, without water softening or demineralisation, you'd also get insoluble Mg and Ca hydroxides dropping out of solution after NH3 injection.

 

[itsmoked]

So, the Anhydrous Ammonia has nothing to do with the pump scaling.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Aqua_man]

Has anyone ever had any experience with the "scale blaster"? As I understand, it's a coil with an electrical charge that wraps around the pipe before and after a water pump. It's supposed to disrupt the calcium as the water passes through the field of charge. But it only lasts for a certain distance so we would need a coil before and after pretty much every pump. Anybody heard of this contraption?

I've also run across magnets that are supposed to do the same thing

 

[EdStainless]

Yes I have experience with various magnetic water treatment equipment.
If you accurately control conditions they do nothing.
Most people that try them and think that they work have actually made changes to the system when they installed it and that is what caused the changes.

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P.E. Metallurgy, Plymouth Tube

 

[bimr]

Complete waste of time. If you like, I will be happy to make you the same guarantee.

First, send me the $1,500. Then do nothing. If you are still having the problem, you can ask me to send the money back to you.

These foolish gadgets have been around and sold for at least 50 years.

This site lists some of the common scams:

Water Treatment Scams

 

[Aqua_man]

Awesome! Thanks for the help, this forum is great!