Cooling Tower - Water Treatment ? ? ?

[MrSlim]

Sulfuric Acid - good or bad???
We use Sulfuric Acid (25%) to maintain our pH level (8.0) in our Cooling Tower and have since 2005. We also run 3 cycles with conductivity being 2100 and controlled by bleed-off. We add an Inhibitor plus 2 biocides. Our makeup water source is Well water with a pH of 7.1 and conductivity of 700.
Our "new water guy" wants to make changes, the first being; no acid....which is great, but what other options do we have and is the acid as bad as he makes it out to be???

[tunaguy]

Acid programs have been used for decades. Keeping the PH lower helps reduce treatment chemicals. You can substitute phosphates and polymers with just as good results. Your water treatment professional should be able to provide a good program.

Many treatment companies are getting away from acid programs because of liability. The tower galvanizing, piping and chillers can be destroyed if the acid injection or sensing gets out of hand. I've seen insurance companies pay small fortunes for replacing entire systems when the acid goes wild.

Do you have apparatus to measure corrosion such as a coupon corrosion rack? They should be used normally, however they're absolutely necessary with acid programs.

Personally, I'd stay away from the acid programs. The liability exceeds the benefits.

[chilliwilly]

I must say I've never heard of adding sulphuric acid to water to balance its ph. I understand the theory of it from school, but I thought you could add other chemicals to water that aren't corrosive to maintain it ph level. I suppose if its worked since 2005 you could say its tried and tested.

Just as a matter of interest in the unlikely event of the water level dropping or drying up due to the top up system not working. Won't this increase the concentration of acid? And in doing so cause other potential problems?

[MrSlim]

We added a coupon corrosion rack recently and I'm waiting for results and will post. I don't know about the possible increase in concentration of acid if we lose water........due to bleed; no..........evaporation; good question.

[INTECHBILL]

Water treatment for all water systems has advanced greatly over the past few years with new wetting agents, oxidizers , glycols and many other.. , best bet is always to remember or keep in mind that your always maintaining a swimming pool, no matter what it's always gonna be the same principles. TDS, Algae eating agents, PH, and all others... Be very careful on new companies with new products that havent been tested extensively.. Chemical demand on a tower in New York will be much different in Los Angeles. :pop:

[tunaguy]

We added a coupon corrosion rack recently and I'm waiting for results and will post. I don't know about the possible increase in concentration of acid if we lose water........due to bleed; no..........evaporation; good question.

I'm not that sure posting corrosion rates would be constructive. You need a few coupon tests along with a dozen other water chemistry levels in order to develop a good corrosion trend. You really need a qualified water treatment professional on site that's familiar with the local water chemistry.

It sounds like you liked the old water treatment company personal and now they hired a new company. The new company is making suggestions that make you uncomfortable. I would give the new company a fair try.

Why didn't the old company install or suggest coupon corrosion racks? These corrosion tests are absolutely necessary on an acid program. Were there loud audible alarms if the PH exceeded a certain level? Did the PH controller add water to the tower basin if PH level is to high? It may be a mute point now if you're going to change programs, however I'd be very nervous using an acid program without constant monitoring and safety devices. Suggesting a non-acid program sounds like good advice to me.

Your original post asked two questions. Do acid programs have inherent risks and if so, are there viable options? I believe almost every qualified person would answer yes to this question. They will however give you varying opinions concerning alternative programs.

You can always monitor your new company by recording chiller performances, taking pictures of tower(s), and having the corrosion coupons tested by an independent laboratory. Be sure that coupon racks have the correct flow too, not too high or too low. Good luck with your decisions.

[dgruber]

Total Dissolved Solids

We always had to keep TDS in check.

City or County water will vary in all locations.

Alkaline for corrosives could be a issue in some areas.

Hydrochloric acid may be an option in some areas to keep PH in check.

[MrSlim]

The options we have been given is to soften the make-up water for the Cooling Tower (existing well water is 450 ppm) or switch to city water, which has 300 ppm hardness.
A few years ago we had to use city water due to a Well problem, the conductivity dropped which stopped the bleeding, but the pH was still maintained by acid.
We do have a high pH alarm, but it isn't connected with the make-up or bleed valve.

[snipe70e]

Me I am opposed to using acids on cooling towers!

I know acid systems can be set up to run higher cycles and that means less chemicals and water used. Ie less money. If the system is monitored through out the day.

My opposition is due to safety. The benifits do not out way the dangers.

Let me give two examples that happen in plants where I worked. Both towers had 99% H2SO4 and a Unilock chemical control system.

In one of the stores that I maintained I changed the 100# carboy one day. The next time I was in the store 2 days later and the carboy was empty. Tower PH 4.0.

The second case was in the boiler chiller room of a state university. The tubing from the acid pump to the injection point broke. The acid was pumped onto the smooth cement floor. When the boiler operator noticed it, he ran to the unilock to turn off the pump. Slipped on the acid and fell on his back. Got up ran to the shower in the locker room. He lost all his clothes in the shower. He was lucky.

I also had a janitor mistake the acid carboy for a floor wax drum. Lucky we headed him off and no one got hurt.

I DO NOT LIKE ACID SYSTEMS.

[MrSlim]

Total Dissolved Solids

We always had to keep TDS in check.

City or County water will vary in all locations.

Alkaline for corrosives could be a issue in some areas.

Hydrochloric acid may be an option in some areas to keep PH in check.

If we switch to city/county water, what are some of the issues we will need to deal with?

[waterworld]

Mr. Slim-

300 ppm of hardness? Man O Man! Sulfuric acid would help, sure; but the safety concerns are legit. If you go with a softener, then your next issue would be Chlorides. You need to talk to your Water guy. There are special Zinc and Phosphonate based chemicals that you need when using soft water on a tower. Chloride levels are going to be high because of the ion exchange reaction- this will result in high corrosion rates if you don't have the right chemical program.

Another option would be to use a phosphonate-polymer chemical program with a CaCO3 stripper (cathode unit inside a reaction chamber on a sidestream). These claim to work without chemicals but trust me, they don't protect against corrosion. That's what the chemical program would supplement.

Let me know if you have any other questions!

[waterworld]

I forgot to ask. Do you know what the Silica levels are in the well and/or city water?

[tombeaux]

As a plant operator alone at night . I too dont like acid for the FUBAR possibilties. I have had tubing fail and have gotten sprayed before . I was lucky I had my FFR on while simply doing a visual first shift check of the chem station . MURPHYS LAW

[MrSlim]

I forgot to ask. Do you know what the Silica levels are in the well and/or city water?

I'll have to research the "Silica levels". Since my first post we have decided to go with non-softened city water. We have stopped pumping acid and are still using an Inhibitor and 2 biocides.

[MrSlim]

Let me know if you have any other questions![/QUOTE]

Sure, all I have are questions...........Inhibitors??? As a result of cold weather and low load, we are not bleeding much water from our systems (3,000 gallons in 14 days). I've always been told that we lose inhibitors, due to bleed and that is why we must continue to add inhibitors. I have not made any adjustments and we are adding the same amount of inhibitor as we did when bleeding almost 2,000 gallons of water a day, yet with almost no bleed we are still losing Inhibitor. Am I wrong about Inhibitor building in a system or do I need to start looking for a cause?

[waterworld]

Sure, all I have are questions...........Inhibitors??? As a result of cold weather and low load, we are not bleeding much water from our systems (3,000 gallons in 14 days). I've always been told that we lose inhibitors, due to bleed and that is why we must continue to add inhibitors. I have not made any adjustments and we are adding the same amount of inhibitor as we did when bleeding almost 2,000 gallons of water a day, yet with almost no bleed we are still losing Inhibitor. Am I wrong about Inhibitor building in a system or do I need to start looking for a cause?

I'm sorry, I really dropped the ball on my reply. Did you still have questions about this?

The reason(s) you are likely using the same amount of inhibitor per day regardless of bleed could be two things:

1. The tower is overflowing and therefore the bleed meter is not registering the bleed and in combination with this, the inhibitor is set to pump with the makeup. This would keep inhibitor usage consistent throughout the year as well as waste water and chemical.

2. The more likely is that the controller is set to feed on a percentage of run time. If the tower is circulating 12 hours a day in the summer or winter, (to prevent freezing) then the controller will still feed or if the tower is off for the majority of the time during the winter, then the flow switch on the sample line could be stuck open or the flowswitch could be bypassed by a jumper in is registered as 'Always On'

Organic inhibitors, like phosphonate do degrade. However it is a slow process and even at 3,000 gallons in two weeks, you should not see it drop that fast. Most Phosphonate inhibitors like PBTC and HEDP, (check your MSDS) are fairly stable. You could use a polymer only program if your water conditions are right. But it is not normal to use the same amount of inhibitor year round because evaporation is so low in the winter and therefore bleed is lessened.

Solutions:
Check your controller when the condenser pump is off. If it says 'Flow' then open the flowswitch housing and clean it out. If the flowswitch is bypassed in the guts of the controller, then make the flowswitch the primary lockout, (usually a jumper inside the controller).

Check the overflow drain. It should be dry. If it is wet, then check the float and make sure it is off, (when the condenser pump is off). If it is running, then adjust the float or, the better solution is to replace it with a conductivity contacting switch and makeup solenoid.

Check the controller for how it is setup to feed. If it is percentage of time and your condenser pumps run constantly, change it to 'Bleed then Feed'. This will feed chemical only after the system bleeds. You should also change the feed time percentage to '50% of bleed' and make the speed and stroke on the inhibitor pump both to '50'. You can then test over the next few days and adjust the speed dial down or up based on your inhibitor levels. DO NOT adjust the stroke. Below 50% will likely cause the pump to lose prime, especially if it does not run very often in the winter.

If you post your makeup water chemistry, specifically the Total Hardness, Total Alkalinity, Chlroides, Silica (if you can get it) and conductivity, I would be happy to let you know what the ideal setpoints on the controller should be in order to maximize your system.