Water Treatment Questions Welcome!

[waterworld]

Thanks. Yes it is a very useful manual. The best part is that it is free. You can print it, share it with as many people you want, or whatever.

For those that have questions about chemical free devices, somewhere in there it says something about how the 'Military does not recongnize the validity of chemical free devices and they are not to be used on D.O.D. owned equipment at any time' I am paraphrasing, but essentially that's what it says. It really pissed the Dolphin people off!

[soonerfan]

I have something that I would like to pick your brain about. I have a site that I take care of that uses well water as the primary condenser water make up and the city water is secondary. Basically, it always makes up with well water unless for some reason the well pump is down. Over the last couple of years the condenser approach temps on the chillers have been climbing even with good maintenance. When the heads are dropped to punch the tubes a whiteish substance seems to be stuck to everything. Brushing doesn't seem to help. I have called the chemical treatment guy a couple of times to come look at this. He checks everything, even takes samples to a lab, and all he can come up with is that it is the quality of the well water that is causing this. They have chemically cleaned the tubes a couple of times and the approach is slowly coming back down, but is there something that they can do to prevent having to chemically clean the tubes? I'm not a big fan of that as it can affect the copper tubes if not done properly. Just don't know if there is something that I should be asking them that they are not thinking of perhaps.

[waterworld]

I have something that I would like to pick your brain about. I have a site that I take care of that uses well water as the primary condenser water make up and the city water is secondary. Basically, it always makes up with well water unless for some reason the well pump is down. Over the last couple of years the condenser approach temps on the chillers have been climbing even with good maintenance. When the heads are dropped to punch the tubes a whiteish substance seems to be stuck to everything. Brushing doesn't seem to help. I have called the chemical treatment guy a couple of times to come look at this. He checks everything, even takes samples to a lab, and all he can come up with is that it is the quality of the well water that is causing this. They have chemically cleaned the tubes a couple of times and the approach is slowly coming back down, but is there something that they can do to prevent having to chemically clean the tubes? I'm not a big fan of that as it can affect the copper tubes if not done properly. Just don't know if there is something that I should be asking them that they are not thinking of perhaps.

It could be silica scale that is forming. Especially with well water. Do you know if silica has been eliminated as a possibility? What does the stuff look like? Does it look sort of shiney? Silica scale looks like white rough glass, which is what it is essentially. When you chemically clean it, does it come right off or is a lot of it stay on the tubes even after chemical cleaning?

Even if your chemical guy says it's from the well water, he should be able to tell you what it is, Calcium Carbonate, Calcium Sulfate, Silicate, etc. Whatever it is, there is a solution for it I assure you. There is always a solution.

[soonerfan]

Honestly, I don't think I have heard him say what the test results said that it was. Guess I should ask huh? It is a white, almost grey rough substance that is very hard and is really noticeable on the heads and the tube sheets as well as the bottom of the cooling towers. You really can't even scrape this stuff off very easily, not to mention inside the tubes. Sort of sounds like what you are describing as silica. No, it doesn't come right off after chemically cleaning, but the approaches are getting better.

[waterworld]

Yeah, it kind of sounds like silica. Silica is bad. It blocks heat transfer even moreso that calcium. The maximum amount of silica that water can hold is 150 ppm. Any higher than that will scale. The only way to get rid of it is to descale with Hydroflouric Acid, and that is the most dangerous acid to handle there is. The reason some of it may go away with chemicals is because not all of it is probably silica. There might be some chemical, calcium, and bio traped in the craters of the scale. Bottom line though, if it's Silica, your electricity bill is a lot higher than it would be even if it were calcium scale not to mention how much higher it would be if it were 100% clean!

I would do this. Have your water treatment company test the well water for Silica (SiO2) ASAP. Then, have them test the condenser water for the same. Then, run a quick calculation:

Condenser water Silica / Well water silica = Silica Cycles

then comapre it to:

Condenser water Chlorides or TDS / Well water Chlorides or TDS

The should be the same, especially with Chlroides. If the Silica cycles are lower, then you have 'missing' silica. The missing silica is what is on your tubes.

You can do the same equation for Hardness as well. Your water guy should do a water balance test for hardness on all service visits. He runs Chlorides (Salt) first which is dead on accurate and doesnt fall out of solution ever and compare those cycles with everything else. If there is missing hardness, there is scale.

You can even to the opposite with heavy metals. Test the city or well water for iron or copper, then test the condenser water. If there is 'extra' iron or copper, something is corroding.

Sorry, I can be long winded sometimes!

[sigma]

As for the temperature of the sulfite test. This is debatable, but in my opinion, below 100 degrees is where you want to be for the most accurate reading. Here is why; Sulfite is unstable and wants to become sulfate, but in order to become sulfate, it needs something to force the reaction, the something is heat. When you take your boiler sample, you must fill the sample bottle all the way to the top to ensure that all the air is gone. Then cap it. Take the sample to a faucet and cool it off. If you leave it open to atmosphere to cool off, the sulfite will consume the oxygen and you will get a low reading on the test. The same goes for testing a hot sample. The short time the hot sample is exposed to air, you are converting SO3, sulfite to SO4, Sulfate.

I always cool the tightly caped water sample to room temperature. My calibrating solution is also in room temperature, so if I want to check accuracy of my conductivity meter I don't have to wary about meter's temperature compensator working correctly.
Speaking about minimizing exposure of sample water to atmosphere during sulfite test, my water treatment rep suggests not to stir water sample after adding acid starch, just do it while drops of iodide are being added.
Do you agree that boiler water sample should be obtained from the lowest port on boiler?
Very thin coat of scale supposed to help protect tubes from pitting. What is your take on this? Scotch marine boilers have large volume of water so after inspection, filling them up with soft water, takes a long time. How much scale would be deposited on tubes if boiler was initially filled with tap water and after that supplied with soft feed water. Let me mention that present treatment does not include phosphate.

[waterworld]

I always cool the tightly caped water sample to room temperature. My calibrating solution is also in room temperature, so if I want to check accuracy of my conductivity meter I don't have to wary about meter's temperature compensator working correctly.
Speaking about minimizing exposure of sample water to atmosphere during sulfite test, my water treatment rep suggests not to stir water sample after adding acid starch, just do it while drops of iodide are being added.
Do you agree that boiler water sample should be obtained from the lowest port on boiler?
Very thin coat of scale supposed to help protect tubes from pitting. What is your take on this? Scotch marine boilers have large volume of water so after inspection, filling them up with soft water, takes a long time. How much scale would be deposited on tubes if boiler was initially filled with tap water and after that supplied with soft feed water. Let me mention that present treatment does not include phosphate.

Everything you said sounds fine, except the "very thin coat of scale" part. No scale is what you want. I going to try and be diplomatic about this, but I have to say that if your water guy said that, well... get a new water guy.

It is true that scale blocks corrosion from oxygen pitting, but a much, much more sever type and almost undetectable form of corrosion is likely to take place. It is called underdepost corrosion. The metal underneath the scale gets no treatment whatsoever, and the tube could very well corrode and rupture. Also, the amount of heat insulated by the scale could very well cause the tube to rupture just from overheating. There is no such thing as good scale, ever. Pitting is caused by oxygen. To avoid this, make sure the DA temperature is at least 212 degrees and use an oxygen scavenger.

As for your question about the soft water. If you use city water, then you have to excpect that nearly all of the hardness will scale the first time you fire the boiler. How much will it be, well if a steam boiler holds say, 5,000 gallons of water (41,700 lbs of water), and that water has 200 ppm of hardness, then by a very rough calculation, you will be leaving 8.3 lbs of CaCO3 scale inside the boiler. That may not sound like a lot, but even a very minute amount on the tubes is bad.

Attachment 138031

The above picture is from a 30 year old water tube boiler that is still in service. As you can see, there is no scale at all, you can also see the blackish-red magnetite layer on the metal. This is what your boilers should look like when inpected. If they don't there is something not right. It could be softener problems like channeling, or leaking heat exchangers, or improper chemicals being used. You said you are not using Phosphate. Are you using Phosphonate? If not, then why? Phosphonate/Polymer programs are excellent and they can be very forgiving if softener problems arise and aren't caught right away.

[waterworld]

Honestly, I don't think I have heard him say what the test results said that it was. Guess I should ask huh? It is a white, almost grey rough substance that is very hard and is really noticeable on the heads and the tube sheets as well as the bottom of the cooling towers. You really can't even scrape this stuff off very easily, not to mention inside the tubes. Sort of sounds like what you are describing as silica. No, it doesn't come right off after chemically cleaning, but the approaches are getting better.

Soonerfan-

I thought of something after my post last night... this may be a stupid question, but does the fan on your tower work? What is the temperature of the condenser water? I have had towers where the VFD failed and the water temperature climbed to 120 degrees plus. Calcium scales like a champ at that temperature when you are cycled up and the scale it makes is damn hard because of the heat. You may want to check that out.

[sigma]

Everything you said sounds fine, except the "very thin coat of scale" part. No scale is what you want. I going to try and be diplomatic about this, but I have to say that if your water guy said that, well... get a new water guy.

I think that I've red somewhere about scale blocking pit corrosion. It was not my rep's idea.
The only thing is, he did not disapprove initial filling up the boiler with hard water.
I will push him to add phosphate to the treatment.

[waterworld]

Sigma,

Okay! BTW, it will block pitting but it is not the desireable nor cost effective way to do it. Ask your water guy about using a Phosphonate, not phosphate. I would specify a single product that contains the following:

PAA -Polyacrylic Acid (Polymer)
HEDP - 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (Phosphonate)
OH - Sodium Hydroxide (Caustic)
Gluco - Sodium Glucoheptonate (Iron Chelant)

If your OH alkalinity remains low, add a supplemental amount of Sodium Hydroxide (Caustic) directly to the chemical tank that has the above product in it to get the OH Alkalinity between 200 and 800 ppm.

You will still need an oxygen scavenger for to avoid pitting. If it is for HVAC or standard steam production use Sodium Sulfite. If it is for power generation, use DEHA. Your water treater should be familiar with both.

For Condensate protection, that depends on the length of the steam line system. Also depends on the pressure of the steam. Let me know the average pressure (psig) and roughly the extent of the condensate system AND whether or not the steam comes into contact with food or surgical instruments. I can recomend an amine based on that.

Hope this helps! Feel free to ask if you need anything else!

[sigma]

Hope this helps! Feel free to ask if you need anything else!

Thanks WW. I appreciate it.
There are two low pressure boilers 400 HP each. Steam pressure is 6-9 psi. All heat exchangers are in mechanical room so are condensate lines. There is no DA just plain condensate receiving tank. Feed water is not heated. Oxygen from makeup water has to be removed by sodium sulfite. All condensate comes back to the tank except from two steam oil heaters mounted on boilers.
I think that treatment guy was planning to use amines for condensate lines protection but changed his mind because feed water lines are made of copper,or maybe he meant different chemicals but for sure, copper pipes were the problem.

[Shophound]

Mr. Waterworld,

Wow. I began reading your OP at around four AM this morning while bringing up my standby boiler after the initial one failed and woke me up around 1 AM.

I think my water chemistry guy is great, but I've been wanting to learn how to independently monitor our plant's water quality for some time, now. We already do this to a certain extent: daily I measure boiler conductivity and sulfite levels, and make-up water hardness (city water ran through a softener). In the chiller room there's an electronic monitor for the tower water conductivity. Once a month I bring down samples from our building hydronic loop, steam condensate, and a water cooled condenser for my guy to test. Each time, more or less, he says things are well, but if not he tells me what to add to correct it.

However I don't have kits available, nor know what to purchase, so I can independently monitor tower water pH and other parameters apart from conductivity. I'd also like to monitor steam condensate pH and etc. independently...all of which would require I know what the acceptable parameters are and what to do to correct any abnormalities.

I will read the links you have provided over the next several days...perhaps the info there states what I should look for in test kits, and what I need to measure. If you already know a good test kit for each area of concern, I'd appreciate any info you might have.

[dandyme]

did i miss the username & password for asereports?

[waterworld]

I think that treatment guy was planning to use amines for condensate lines protection but changed his mind because feed water lines are made of copper,or maybe he meant different chemicals but for sure, copper pipes were the problem.

I would still use amines even if the system is all copper. The danger of corrosion in the steam system is from carbonic acid (H2CO3). Steam is almost pure water. The problem with pure water is it doesnt like to be pure. It wants dissolved solids and the major problem in steam lines is when the steam condenses from a gas to a liquid, it absorbes CO2. The CO2 reacts with the hydrogen in the water and forms carbonic acid. That is why the pH of condensate is so low, usually in the high 5's or low 6's. Copper is stable at a pH of 6.5 and above because of an oxide film. Unfortuantely, that oxide film gets ripped right off by the carbonic acid and the pipes begin to disolve very quickly. Then, the disolved copper comes back into the DA, or in your case the feedwater tank, and begins to corrode the mild steel walls of the tank. Then, (there's always another 'then') the corroded iron begins to plug up strainers as well as becomes iron scale on the boiler tubes.

It is so important to keep condensate pH at a minimum of 7.8, (preferably at 8.2 in my opinion) but no higher than 9.0, (again I prefer 8.8 at the high end) or copper begins to corrode again. Copper is only safe at the pH ranges between 6.5 and 9.0.

Now, you next problem is going to be that the only pH neutralizing amine that will work in a low pressure steam environment is Cyclohexylamine. The option most water treatment companies try is Morpholine, but it won't work. You need at least 20-30 psi in the steam lines for Morpholine to flash and become a vapor. Cyclohexylamine requires very little pressure and does an excellent job. It's also quite economical. But just a word of caution, feed it at a very slow rate and build it up from there, It is very potent at low levels and the pH could easily sky rocket within minutes. Start at the lowest possible dosage and slowly raise it over a period of a few weeks.

Oh yeah, for all of the Global Warming people, (I am not trying to be offensive to any of you) the process of water absorbing CO2 is not unique to boilers. When it rains, the rain literally strips the atmosphere of CO2. That's what so called 'acid rain' is. See- no worries, nature has her own filters!

[waterworld]

Mr. Waterworld,

Wow. I began reading your OP at around four AM this morning while bringing up my standby boiler after the initial one failed and woke me up around 1 AM.

I think my water chemistry guy is great, but I've been wanting to learn how to independently monitor our plant's water quality for some time, now. We already do this to a certain extent: daily I measure boiler conductivity and sulfite levels, and make-up water hardness (city water ran through a softener). In the chiller room there's an electronic monitor for the tower water conductivity. Once a month I bring down samples from our building hydronic loop, steam condensate, and a water cooled condenser for my guy to test. Each time, more or less, he says things are well, but if not he tells me what to add to correct it.

However I don't have kits available, nor know what to purchase, so I can independently monitor tower water pH and other parameters apart from conductivity. I'd also like to monitor steam condensate pH and etc. independently...all of which would require I know what the acceptable parameters are and what to do to correct any abnormalities.

I will read the links you have provided over the next several days...perhaps the info there states what I should look for in test kits, and what I need to measure. If you already know a good test kit for each area of concern, I'd appreciate any info you might have.

I will post some links to good test kits for you later this evening. Beleive me, double checking is a must. My customers trust me, (I hope) but I always provide test kits for them. I figure it's in my best interest to have them keeping an eye on the systems so there will be no suprises for me when I come in to perform testing. Unfortunately, at least in Southern California so many Engineers have stopped testng or being involved with the chemistry side of things and have left it to thier chemical guy. This has led to a lot of BS in this industry and a lot of poor quality water treatment companies that are lest than honest about things. I am glad to see your interest in making sure your systems are protected!

It's like the Great Man said, "Trust, but verify"

[waterworld]

did i miss the username & password for asereports?

No, you didnt miss it. ASeReports is our web based service report site. All of our service reports are online, as well as our customers testing logs. It's really neat, we can put together trend reports, monitor our controllers live over the web with wireless cards where we can check chemical levels on tanks, live controller readings, MODBUS, etc.

I better stop before I get in trouble for trying to be a salesman. Unfortunately the site is for our customers only, but I will ask my boss if I can post the guest username and password for this site. I will let you know.

[dandyme]

just interested in sticking my nose in the library


( the note at bottom of part of those docs )

[HuNGRYTeCH]

Waterworld, I have a set of Trane Intellipak II RTU's that have water cooled condensers. It is a lot like a water tower except the coils are wound up tubing in a circle about 1.5 feet thick. I have a little bit of calcium build up on the coils (about 1/16") and a lot of calcium scale in the sump. The city water in this area has a lot of hard water minerals. I have talked to Trane a few times and they keep telling me that 1. These units self manage hard water build up by the expansion and contraction of the copper coil and an auto drain and refill (about 50% of the sump every 8 hours) and 2. That I can not use convential chemicals because there is some galvanized steel in the water tower, so only organic chemicals can be used. I have tried using an orange citrus organic water treatment and it does almost nothing compared to an acid which eats the calcium in minutes. I am curious if you have an experience with these units (there seem to be very few of them, only 3 in Colorado and I have 2)? And also what your opinion is on the "harmful" effects of acid water treatment is on copper and galvanized steal vs the organic citrus treatment.

A side note, I am trying to get this customer to install a water softener to supply treated water to the RTU's.

[waterworld]

Waterworld, I have a set of Trane Intellipak II RTU's that have water cooled condensers. It is a lot like a water tower except the coils are wound up tubing in a circle about 1.5 feet thick. I have a little bit of calcium build up on the coils (about 1/16") and a lot of calcium scale in the sump. The city water in this area has a lot of hard water minerals. I have talked to Trane a few times and they keep telling me that 1. These units self manage hard water build up by the expansion and contraction of the copper coil and an auto drain and refill (about 50% of the sump every 8 hours) and 2. That I can not use convential chemicals because there is some galvanized steel in the water tower, so only organic chemicals can be used. I have tried using an orange citrus organic water treatment and it does almost nothing compared to an acid which eats the calcium in minutes. I am curious if you have an experience with these units (there seem to be very few of them, only 3 in Colorado and I have 2)? And also what your opinion is on the "harmful" effects of acid water treatment is on copper and galvanized steal vs the organic citrus treatment.

A side note, I am trying to get this customer to install a water softener to supply treated water to the RTU's.

First of all, 1/16" of scale is a lot. The fouling factor for 1/16" of an inch is roughly 60%. That means your condenser's ability to transfer heat has a reduced efficiency of 60%.

An example regarding the increased cost for running a 400 ton fouled chiller condenser at that fouling factor is:

320tons (400 tons @ 80% average load) X 0.50 (KW/ton) X 8 (Hrs per day) X 365 (Days per year) X 0.05 (Cost per KW Hour) = $23,360 per year in electricity costs IF THE CHILLER IS NOT FOULED.

To calculate the additional electricity you would spend:

23,360 x 0.60 (Roughly the fouling factor for 1/16" of scale) = $14,016 in additional electricity costs!

Okay, so how to avoid this. Galvanized systems can use acid. The key is to keep the pH up above 8.5 or so. Below a pH of 8.0, the Zinc in the galvanization begins to dissolve. The absolute biggest mistake I see when people use acid is that they run the pH in too wide of a range. Let's say your target pH is 8.3, here is the mistake so many people make-

The controller is set to turn the acid on at 8.5. So far so good. The controller however is set to turn the acid off at 8.2. That is BAD. When the acid is fed, it takes some time before the acid effects the bulk water to drop the pH, so by the time the pH probe reads the bulk water's pH at 8.2, there is still alot of acid in the system that will eventually drop the pH into the 7 range. This will kill a galvanized tower! On all the towers I take care of, I use a deadband of 0.05, in the example above, the acid comes on at 8.5 and off at 8.45. That way I am assured that even if the acid overfeeds a bit, it wont drop my pH down below the 8 mark. The key is not to shock the metals, keep the pH as close to the taget at all times, and test the pH everyday!

Now, as far as organic tower treatments, good old Phosphonat is organic. I would use a Phosphonate based inhibitor with Azole to protect copper. You may be able to run that type of inhibitor without acid as well. Just keep the total alkalinity below 500 and the phosphonate residual around 6 - 7 ppm as PO4.

What I would do first though is call a Company in Canada, (I don't work for them) called Magnus They have a two part cleaner-descaler that is excellent! It leaves the tubes and sump black, which is ugly, but it is a magnetite layer that protects everything. It really is a great product and puts Rid-Lyme to shame. My company makes descalers also, but when I need one, I get the product from Magnus.

[waterworld]

just interested in sticking my nose in the library


( the note at bottom of part of those docs )

If you are looking for something specific, I am sure I can smuggle it out for you. Let me know what you are looking for!