In this episode of Chemical Processing's Distilled podcast, Editor-in-Chief Traci Purdum talks with water treatment expert Brad Buecker about the hidden risks of remote cooling systems scattered around large plants. Buecker explains how scale formation and microbiological fouling quietly degrade heat transfer, why cooling towers concentrate impurities and complicate chemistry, and why monthly vendor visits often aren't enough. He stresses online instrumentation, reliable biocide feed and trained staff who act on data. Buecker also shares cautionary tales, including a boiler kept online to earn $30,000 that required more than $2 million in repairs, and his family's connection to Legionnaires' disease.

Transcript

(Edited for clarity)

Traci: Welcome to Chemical Processing’s Distilled podcast. This podcast and its transcript can be found at chemicalprocessing.com. You can also download this podcast on your favorite player. I’m Traci Purdum, editor-in-chief of CP, and joining me once again is Brad Buecker, frequent contributor and podcast guest, talking about all things water and wastewater, and then some.

He’ll also be our guest speaker on the Field Notes LinkedIn Lunch and Learn series on Oct. 29. Brad is a senior technical consultant with Samco Technologies and has many years of experience in or supporting the power industry, much of it in steam generation chemistry, water treatment and air quality control.

Brad has a degree in chemistry from Iowa State University, with additional coursework in fluid mechanics, energy and materials balances, and advanced inorganic chemistry. Welcome, Brad. Thanks for joining me again.

Brad: Thanks, Traci. It’s good to be back.

Early Signs Of Cooling Tower Failure

Traci: Today’s topic is an important one: remote cooling systems. Large plants may have a number of cooling systems scattered around in out-of-the-way places, and operator inattention can allow problems to fester until they suddenly become major. Although when a remote cooling system fails suddenly, it usually isn’t sudden at all. So what are the earliest, easiest-to-miss signs that one of these out-of-the-way systems is deteriorating, and why do operators so often overlook them?

Brad: In the first place, with these systems scattered around, especially at large utilities and industrial plants, it can be easy to overlook some of them, particularly the small ones. So you need good records and a procedure to inspect them.

As for early detection, some of this comes from my own experience, which I’ll get to in a few minutes. In cooling systems, scale formation and microbiological fouling obviously degrade heat transfer. With a good monitoring program and someone experienced and properly trained, you can detect these problems before things get serious.

I’ve dealt with microbes a lot, and in my opinion — and many of my colleagues agree — they can be the No. 1 problem. So, proactively, you need a good microbiological feed system that’s set up and operating properly, because conditions can get out of hand very quickly.

For several years at both of my power plants, I used a monitoring program specific to one kind of heat exchanger, the steam surface condenser. It was based on calculations developed by the Heat Exchange Institute and the General Physics Corp., which is now GP Strategies. It allowed me to detect performance changes from microbiological fouling, scale formation or excess air in-leakage very early on. In many cases, we could make adjustments to correct the problem, or, if conditions escalated, we could plan to alleviate them. That program proved to be wonderful.

So one thing I recommend is having somebody at the plant who can look for these issues and catch them before they become serious. I’ll talk about this more at the Field Notes Lunch and Learn on Oct. 29 and show a few photos that illustrate what can happen, including collapse of cooling tower fill due to microbiological buildup, as well as fouling, flow restrictions and corrosion in heat exchangers.

Some plants don’t have enough staff or sufficiently trained personnel to do these tasks. I’ve been at a number of plants like that. This gets into one of my soapbox issues: being proactive versus reactive. Much money can be saved by having staff who can catch these conditions and take care of them before they become huge problems.

Relying on a once-a-month water treatment vendor visit may not be enough. I’ve seen microbiological fouling take over within days. Water treatment vendors are very important for analyzing samples and recommending chemical treatment programs, but periodic visits often don’t cut it.

Cooling Towers Vs. Once-Through Systems

Traci: Why are potential problems often exacerbated in systems with cooling towers compared with once-through systems?

Brad: In a cooling tower, evaporation of a small portion of the recirculating water — maybe only 1% to 3% — carries away most of the heat. That water leaves as essentially pure water, so the circulating water concentrates. This is known as cycles of concentration, and both dissolved and suspended solids increase as the water evaporates.

In my experience, a very common range is four to six cycles of concentration. That doesn’t allow the water to concentrate too much, yet it reduces blowdown requirements a fair amount. I have a graph in the Lunch and Learn presentation that shows the relationship among evaporation, cycles of concentration and blowdown.

Here’s a simple example that shows how the chemistry can change and problems can occur. Take a hypothetical cooling tower operating at five cycles of concentration, and say the inlet water has 100 parts per million each of calcium, bicarbonate alkalinity and chloride. At five cycles, those concentrations all increase to 500 ppm. That could easily exceed the saturation limit of calcium carbonate, and other scales could potentially form too — calcium sulfate, silicates and so on. Plants use chemical treatment and blowdown from the cooling tower basin to control the chemistry, but it adds complexity, requires closer monitoring and can increase chemical costs.

Going back to chloride, I saw something interesting when I was with one of my engineering firms. For a number of years, I was part of a team that reviewed specifications for new combined-cycle power plants with heat recovery steam generators and cooling towers. The engineering firms that specified these systems would almost automatically call for 304L or 316L stainless steel condenser tubing. But when we looked at the water quality data, in many cases cycling up in the cooling tower would push chloride past the concentration that causes pitting corrosion. I don’t think the firms that designed the specs had chemistry people on staff who understood this. So we’d get a project that said, “You’re going to build it like this,” and we’d be telling our construction and engineering people, “You’re going to run into problems here.”

We occasionally saw the same thing with raw water sources that could enhance microbiological fouling. That can occur in any cooling water system without additional treatment, and engineering staffs often don’t have people who recognize it. So those are big issues with cooling towers.

Traci: Were you able to resolve that? Did they switch out the materials of construction?

Brad: In some cases, yes. It involved talking with the client and pointing out the problems with what had been designed and what needed to be done.

On one project — this was on the microbiological side — we realized the initial raw water treatment for the entire plant, including the cooling system, would not remove the nutrients that enhance microbiological fouling. We explained the trade-offs to the client: Without a treatment system to remove those materials, the cooling tower would have to be much larger and less efficient. The economics clearly favored the treatment system over a much larger cooling tower. So yes, some people do understand the need for adjustments.

Monitoring And Walkdown Rountines

Traci: I want to dial back a little. We talked about staffing issues, and large plants may have many cooling systems, both open and closed, with perhaps not the best coordination regarding which department monitors them. How should a plant assign accountability for these systems, and what’s the minimum monitoring and walkdown routine you would insist on?

Brad: Those are good questions, with a number of potential answers. It’s not always black and white. There are gray areas where you could do things one way and be in decent shape, or be a little more proactive and have a better system.

From my own experience — and this covers not only cooling water but steam generation chemistry — I’d want online instrumentation that provides immediate feedback, so operators and technical personnel can monitor conditions and make adjustments promptly. For open cooling systems with cooling towers, I’m looking at specific conductivity, pH, oxidizing biocide residuals and possibly corrosion and biofouling monitors. Again, it’s about early detection — catching things before they get out of hand.

If there were one item I’d insist personnel examine consistently, it’s the biocide feed system. At the plants where I worked, auxiliary operators walked around each shift and checked equipment. I’d have them check the operation and performance of the biocide feed system on the units that need it, because if that system goes down, microbes can really go to town in a short time.

The top water treatment companies have software programs that, if the online instrumentation is in place and producing good data, will track that data and flag conditions that might be getting out of line. Some companies offer services where the data also goes to their facility, and their people review it regularly and offer suggestions. That’s an option, too. But in my mind, it comes down to good instrumentation — and, to get back on my soapbox, personnel who understand what the data means and act on it.

Case Studies

Traci: Can you walk us through any real cases — you don’t have to name names — where neglect of a cooling system upset escalated into a big event? What was the root cause, and what single change would have prevented it?

Brad: Oh yes, I’ll give you one. It’s maybe not quite down the straight path we’re discussing, but it’s very close, and it shows the need to act when things happen. Actually, I’ve got a couple.

The first was at a power plant, on one of the smaller units, which operated at only 1,250 psi boiler pressure — and many large industrial plants have boilers that operate at or near that pressure. This was early in my time at the facility. The unit had just come off a regularly scheduled maintenance outage, and we noticed a condenser leak allowing raw water into the condensate going to the boiler.

You don’t want cooling water impurities going into a boiler, because they cause scaling and corrosion, which can be very severe, as we’ll see.

We contacted operations right away and said, “You need to shut the boiler down. There’s too much contamination coming in.” Operations said, “Oh no, we’re selling power. We have to keep the boiler online.” So we worked as hard as we could to keep the unit chemistry in order, feeding the proper chemicals, but it was essentially a losing battle.

They operated like that for three weeks. When they finally brought the unit down, they found that cooling water was indeed getting into the boiler feedwater, but from a different source — that’s a whole separate story. The effects were the same, though. Within about two months, boiler tubes started to fail, sometimes within hours of each other.

I don’t remember the number exactly, but I heard the power sales they kept the boiler online for were around $30,000. That spring, they had to take the boiler off and have it retubed entirely. The materials cost was over $2 million.

Traci: Wow.

Brad: And that doesn’t count lost production or maintenance costs. Obviously, the return on investment for running that boiler for three weeks with a leak was very negative.

This goes back to the article I wrote for you a number of months ago about “water is water” — or water is not water. It’s one of the classic cases I’ve always used, because that was the plant operators’ attitude then: Water is water. It was an eye-opener for them. Eventually, they tasked me with being project manager for installing a comprehensive online water/steam monitoring system for the three units at that facility. Again, it’s about early detection, allowing operators and management to shut down units or make adjustments before problems become major.

The other example involved that unit and the plant’s two other units as well. The plant is in the Midwest, so in winter they don’t need to feed biocide; the microbes are inactive. But typically every year in early March, the operations crew would start up the biocide feed system to protect the steam condensers before the water warmed up. The water came from a recreational lake at the plant. One March, when they went to start it up, the system wouldn’t operate properly, and they had to order new parts, which took three to four weeks, as I recall. That gave the microbes, with the water warming up, plenty of time to settle in the condenser tubes and degrade performance. That’s a classic example of the need for maintenance — making sure treatment systems work properly before you need them.

Legionella — A Personal Take

Traci: When I think about these things, Legionella comes to mind. I know you probably have a story on that.

Brad: I do. First, going back to biocide feed systems, we did a lot of cooling water inspections in the plants, and those can be very good places to potentially contract this bacteria. I never had any problems with it, but I’ve heard of power and industrial plant personnel who may have been exposed while inspecting cooling systems.

But there’s a personal story that keeps Legionella at the top of my mind, even though I don’t deal with it that often. In July 1976, the Legionnaires were at the Bellevue-Stratford Hotel in Philadelphia, where they caught the disease that eventually got its name, Legionnaires’ disease. My parents were at that hotel at the same time. My mom called me and said, “Your dad seems to have come down with the flu.”

Traci: Geez.

Brad: They were both in their early 50s and in good health, and he got over it and came home. After the reports started coming out, we figured out what he probably had. But being in good health, he recovered well. So whenever anybody talks about Legionella, I have a personal connection to it, and I’m glad we discussed it when we were reviewing the questions.

It’s still going on. There are still Legionella problems all over. And as news reports show, it doesn’t just come from commercial or industrial cooling towers; it can be in so many different water systems. Hospitals are a great place to pick up Legionella. Potentially even the water sprays on produce at grocery stores. Now, I’m not saying you shouldn’t buy produce. You get Legionella by inhaling very tiny water droplets, not from water sprayed on something. But there are so many sources — hot tubs, decorative fountains — where water spray can be inhaled, and then the bacteria can get into a person’s lungs and start proliferating.

Traci: Do you think your parents’ experience is the reason you went into your career, or was that just a weird aside?

Brad: That was just a weird aside. I had always been interested in chemistry. But I’ll digress for a minute: While I was in college, my dad was a plumbing contractor, which is kind of ironic given that so many Legionella problems occur in plumbing systems. I worked for him long enough, including a year or two after college, to get my journeyman’s license. Plumbers make good money; I could have stayed in that business.

But I wanted to use my chemistry degree. A lab position opened up at a power plant in my hometown, and I ended up getting hired. Power plants, and industrial plants in general, are fascinating places with all the processes that go on. So I went into the power industry and dealt with water and air pollution control, process engineering and performance monitoring. At every stage, there seemed to be something new to discover.

Traci: Well, Brad, I appreciate you being our go-to water guy, often on a soapbox. I think people need to be on a soapbox, especially with everything that’s at stake. I appreciate the time you’ve put into this for us.

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Brad: Thank you, Traci.