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Descaling Cooling Water System

05/07/2012 6:40 AM

Hi I am an electroniv engineer mby training but my new job includes having to look after some controled environments. 6 of there cooling systems run off of a comon cooling tower we have started having problems with one of the heat exchangers cloging up and out local refrigeration guy sugested taking it out of circuit and runing a hydrocloric acid solution through it.

Is this the right solution and if so can I run it through the whole system as I noticed when I took one of the pumps out for maintanance there is scale buildup and rust in the pipes could I run a week solution through the whole system to clear it if so what concintration or ph or what other chemical could I use?

also How can I stop this from hapening in future?

I notice there was a dosing system at on point but it has long synce failed

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#1

Re: Descaling Cooling Water System

05/07/2012 9:15 PM

We used to run a long rod with a brush on the end down each tube and back. The rod had a water hose hook up on the end and sprayed water out in a circle from within the brush....Here is a link provided to a supplier..They make different kinds....

http://www.tcwilson.com/tube_cleaning/reference_charts/smart_tube_cleaning.php

http://www.tcwilson.com/tube_cleaning/small_diameter.php

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#2
In reply to #1

Re: Descaling Cooling Water System

05/07/2012 11:07 PM

Dilute HCl (5 wt% max) is probabaly the best way to go. The solutin shoudl contain a small amount of a HCl corrosion inhibitor and you shoudl follow the acid with a neutralizing passivaton rinse of 1% TSP. This is to ensure the system is at a neutral pH when you return it service. you didnt mention what the meterials of the system are. (sounds liek steel - but you have to watch if you mixed materials like copper or brass with steel. )

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#3
In reply to #1

Re: Descaling Cooling Water System

05/07/2012 11:32 PM

"Most chiller manufacturers recommend cleaning condenser tubes annually, since they typically are part of an open system, and they recommend cleaning evaporator tubes once every three years for closed systems. But if the evaporator is part of an open system, they recommend periodic inspection and cleaning.

Managers can consider two primary methods for cleaning tubes:

  • Mechanical cleaning removes mud, algae, sludge and loose materials from smooth-bore tubes and consists of removing the water-box covers, brushing the tubes and flushing with clean water. For internally enhanced tubes, managers should consult the chiller manufacturer for mechanical-cleaning recommendations.
  • Chemical cleaning removes scale. Most chiller manufacturers recommend consulting with a local water-treatment supplier to determine the proper chemical solution required. A thorough mechanical cleaning should always follow a chemical cleaning.

New chillers feature automatic tube-brushing systems, which can be retrofit onto existing chillers. These systems use small, nylon-bristled brushes that flow through the tubes for cleaning. A custom-manufactured, four-way reversing valve is installed in condenser water-piping system, and every six hours, the system automatically reverses the flow through the condenser tubes for about 30 seconds.
Coupled with proper water treatment, these systems virtually eliminate fouling within the chiller and maintain design-approach temperatures. These systems typically show payback periods of less than two years."

http://www.facilitiesnet.com/hvac/article/5-Steps-to-Chiller-Efficiency--2192

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#4

Re: Descaling Cooling Water System

05/08/2012 12:03 AM

Consult and use their expert advice to carry out the descaling of heat exchangers as it is a professional work

To reduce scaling in future check the quality of water which is used and as per the report install proper chemical dosing system in consultation with the chiller equipment supplier and water treatment expert.

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#5

Re: Descaling Cooling Water System

05/08/2012 12:42 AM

GA to #2,3 & 4, really good suggestions for OP.

"I noticed ........there is scale buildup and rust in the pipes."

You can notice either of these two, not both at a time at same place and may require different solutions.

Simply passing mild HCL without inhibitors and passivassion cycle thereafter will be dangerous for tubes. Selection of chemical & its concentration also depend on tube material.

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#6
In reply to #5

Re: Descaling Cooling Water System

05/08/2012 2:49 AM

thank you for all your input I will try find a local expert to do the relevent cleaning and get our system back on track.

when I removed the ceased pump I noticed on the inlet side there was scaling and on the outlet pipe there was rust this may be due to it being out of service for the last 3 years though.

a bit of further info this system part of a university reaserch facility which has not had anyone maintaining it for the last 4 years. I have now been apointed to maintain the whole system and am now on a steep learning curve when it comes to refrigeration on the controle system side I am verry comfortable as this is the industry I have come from. so I apreciate all the help in pointing me in the right direction on this.

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#20
In reply to #6

Re: Descaling Cooling Water System

02/03/2014 12:19 PM

We use desaling products from Delta Products Group in Aurora, IL in the United States. These chemicals can be held in human hands and do not present any danger to my staff or my equipment like the use of acid does. They restore our equipment to like-new condition and extend its lifespan. Acid only does damage in one way or another. When we clean our equipment, we wear normal work clothes, circulate through the system and done in a day or less. They do ship internationally as well and have for some of our other locations. Just a thought.

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#7

Re: Descaling Cooling Water System

05/08/2012 8:07 AM

Mupwi, Greetings from Florida, USA

In response to your post, let me be very clear on this, whenever you induce acids or alkalines into water loops you sacrifice the internal components to some degree. This damage is irreversable. Great care should be exercised when attempting this. There is another way to do this without chemicals such as acids or alkalines along with then ability to end solids blowdown and chemical use at all. Please forward me your email and I will share a detailed technical study to you. This documentation will be very instrumental in assisting you in your quest to remedy your condition but to also create a return on investment (something not usually avaliable when treating cooling tower water)

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#9
In reply to #7

Re: Descaling Cooling Water System

05/08/2012 8:27 AM

Also one more thing, my method of water treatment doesn't involve "chasing water" after it misbehaves, it involves pretreatment BEFORE it goes into the tower. Clean, green and sustainable treatment of water. Look forward to hearing from you Mupwi!

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#8

Re: Descaling Cooling Water System

05/08/2012 8:13 AM

We have a 300T Chiller that we mechanically (as shown by Solar Eagle on Post 1 - brushes/water) clean the tubes on an annual basis. Part of the value of the mechanical cleaning is that while the unit is open you can make a visual check on the tubes and the ends of the Chiller. A couple of years ago we noticed some wear on the tube ends and had those areas repaired while the unit was open.

We also treat the tower with chemicals with scale inhibitor and also to keep the proper ph in the water.

Just remember "problems don't get better with age or neglect."

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#10

Re: Descaling Cooling Water System

05/08/2012 8:57 AM

Unfortunately our heat exchangers are sealed units and would not be able to axess them with the brush method I think that pretreatment of the water will be the key for future.

For now we will just have to try chemical methods of cleaning and hope we dont need to replace any of them.

Wwhen will finance departments ever learn thas saving on maintanance just ends up costing in the end

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#11

Re: Descaling Cooling Water System

05/08/2012 9:31 AM

Your best bet is to contract with a professional to (1) mechanically clean the condenser tubes, remove any debris from the tube sheet, and assess whether it is best to retube the condenser (and thus start over), or to chemically clean, etc.

The contractor will need all the information on the system in its original format, and you may elect to contact the manufacturer for their recommendations.

If neglected, open cooling circuits will ruin equipment every time. You might even want to investigate the possibility of using closed loop cooling, with the water loop being circulated through a large "air coil" to radiate the heat, but the applicability of this depends on system and ambient temperatures at your location, and it might be necessary to use a pure water spray (from a reverse osmosis system - see Microcool) to further lower the approach temperature.

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#12

Re: Descaling Cooling Water System

05/08/2012 3:56 PM

Contact a local water treatment with a good reputation. They will be able to recommend, design and install a system that continously feeds the proper chemical treatment plus establishing a constnt bleed to prevent this in the future. To begin, they would have to clean out the scale you've built up. This is not a DIY project...for the pros only!

Lou Bindner

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#13
In reply to #12

Re: Descaling Cooling Water System

05/09/2012 6:48 AM

This is exactly the problem with the current technologies available to us in the water treatment industry!!!!! CONSTANT BLEED!!!! Really!!!

Doesn't anyone feel that sending chemicals to the sewer is a waste of water and very taxing our our water system?

The method of loading up the water with chemicals until the chemicals fail then blow them down the drain and starting over is archaic at best. Certainly we can develop a better way than this.

I can send you a technical paper explaining the lets say more intelligent way of treating water, never having scale or micro biological growth and no constant bleed.

Pleeeeese!

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#14
In reply to #13

Re: Descaling Cooling Water System

05/09/2012 3:28 PM

I am well aware of some of the more recent treatments that claim no cooling tower bleed is needed with their technology/process. Basically, one has to change the basic chemical species in the water that produce scale and/or corrosion (many times a corrosion problem is linked to either biological fouling or to under-deposit corrosion beneath mineral scale).

So, the choices are either remove the bicarbonate, carbonate ions, and supplant them with something else - (see HiCycler from Chemico, International), or use well controlled water softening to remove Calcium and Magnesium (also Barium, etc.) and the high salt content in the system will limit bactieral growth, while the dissolved reactive silica in the water becomes a powerfully effective corrosion inhibitor. (search NACE publications for references to high efficiency softening).

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#15
In reply to #14

Re: Descaling Cooling Water System

05/09/2012 5:30 PM

Correct the silica is the key , well along with the calcium and magnesium removal. It's just the theory and application of not chasing water, but being proactive. We have several installations in very large applications that have not utilized their blowdown in two years.

Cheers!

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#16
In reply to #15

Re: Descaling Cooling Water System

05/10/2012 8:53 AM

My final comment on the matter: If high efficiency softening is utilized, diligent care must be given to the maintenance of the softeners, monitoring of regeneration, etc.

Fortunately, even this can be computerized.

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#19
In reply to #16

Re: Descaling Cooling Water System

05/12/2012 12:17 PM

Agreed, there are no water treatment solutions that do not require care. However to the initial generator of this string, mupwi, high efficiency zero discharge softening systems will remove all of the scale without chemical cleaning, period. AND it will develop a return of every cent that you spend. No other system can do that! Along with no blow-down.

I realize that change and new technology makes humans curl up and hide. When Galileo discovered the moons of Jupiter, the astronomers of his time thought he was insane. When Thomas Edison demonstrated the first incandescent light bulb the fellow that was in the gas lantern business said he was insane.

What is more insane than using chemicals to treat cooling tower water when we do not need to do this any longer!!!!!!!

We allow our formal training to destroy our creativity. We become so satisfied with what and how we always did things that when better technology comes along we simply don't take notice. My God, this is an engineering forum!!!!

You are either eyes wide open or eyes wide shut, you decide.

Ok, I'm off of my soapbox!

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#17

Re: Descaling Cooling Water System

05/10/2012 9:20 AM

well had all the experts here to look at the system and they have decided we need to do a chemical flush and install a new dosing system as the old one is non functional planing to do this all in june our coldest month of the year acording to the weather beuro

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#18

Re: Descaling Cooling Water System

05/10/2012 10:28 PM

I assume your cooling tower is of the 'open' variety. That is, the water that collects in the basin is pumped to your cooling units.

If the heat exchangers come apart, clean them by mechanical means. If they don't, clean them chemically as recommended by the manufacturer. Circulate the cleaning solution through the heat exchanger ONLY.

Don't run acid through the whole system. It will ruin the cooling tower's corrosion protection system- presumably galvanized steel- and cause premature failure of the piping.

Find a competent water treatment specialist and follow his/her recommendations.

Start by flushing all the dirt and debris out of the tower. Get on a water treatment program. Consider adding a centrifugal separator or strainers to protect the heat exchangers.

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