As Herbert Henry Oxidane, P.I., walked across the Acme Frisbee powerhouse floor, he dodged the leaks from the pouring, relentless rain outside the aged walls. Known to the metropolis of Waterville as Detective H2O and to his friends as Ox, the water detective considered himself the best water treater this side of the Ohio who liked to solve problems drop by drop. Passing the four 100,000 lb/hr watertube boilers on the way to the powerhouse office, Detective H2O heard his name covertly called.

“Psssst! Ox! Over here!” Melvin, the boiler operator, loudly whispered.

“Whatcha got, Melvin?”

“One of the night shift operators, Tony, keeps messing with the works, Ox. Real bad. He keeps chokin’ off the vent line on the deaerator. Each morning, there’s barely a wisp coming out of the DA. I open the vent valve backup, but he turns it back down every night, see. Like a seesaw. He’s singin’ like a canary to the bosses that we’re wasting steam and money! I think he’s nuts, Ox! If I’m wrong, I’ll own up to it, but what’s the lowdown on what’s right, Ox? What do you say?”

Detective H2O cracked a smile because he knew these two operators. Both good guys. Both proud of and passionate for their profession. Both confident in their abilities. Both competitive. Only one was really correct, of course. Detective H2O would have to do his best to let the incorrect one down gently.

“Well, what does a deaerator do, Melvin?”

“It scrubs the water of oxygen and other gases such as carbon dioxide. Otherwise, the boiler will pit and the condensate lines rot from the inside out,” replied Melvin.

“That’s right,” said Detective H2O. “Now, you could try to treat for oxygen and carbon dioxide chemically, of course, but the American Society of Mechanical Engineers recommends, ‘Where a choice is available, the reduction or removal of objectionable constituents by pretreatment external to the boiler is always preferable to, and more reliable than, management of these constituents within the boiler by internal chemical treatment.’ That’s my favorite line from their guidelines, so I memorized it.”

“Right, Ox,” replied Melvin contemplatively.

“So, the plan is to remove these dissolved gases before they get into the boiler to cause headaches. Deaerators do this by heating up the water to 2 to 4 degrees Fahrenheit of saturation temperatures…or the boiling point,” he added when he saw Melvin’s eyes glaze a bit. “Here, look at this graph.” Detective H2O pulled out his pocket handbook, flipped it open to a dog-eared page and showed Melvin.

“As you can see, the hotter the water gets, the less dissolved oxygen it can hold. The same holds true of other dissolved gasses, such as carbon dioxide. So the first thing is to keep the temperature at setpoint. Tony’s not changing the temperature is he?”

“No, Ox, that holds steady.”

“Good. Once the noncondensible gases are driven off, they have to go somewhere. They can’t just stay there or else they will end up back in the boiler regardless. They have to be vented off. A little steam will sneak out with them, but this is a small price to pay to keep a boiler and all its piping from falling apart around you,” said Detective H2O. “So the white elephant in the room is how much to vent. Industry rules of thumb say the deaerator vent should typically be 15 to 33 inches of actively moving plume. Another rule of thumb is an invisible area should be seen between the end of the vent line and where the plume begins to be visible,” commented the water detective as he sketched it out in his notebook for Melvin to see.

“That’s it, Ox! The wisp of steam Tony keeps making the DA vent can’t be anywhere near enough! He said it was, but it isn’t. I knew it!”

“How are the sulfite levels behaving in the boilers, Melvin?”

“Hmmm…I have to turn down the sulfite pumps at the end of each of my shifts. Next morning, I find that Tony has turned them back up with notes telling me not to mess with the pump settings,” replied Melvin.

“That makes sense. If the deaerators are removing less dissolved oxygen because of inadequate venting, it will take higher sulfite levels to react with it. In the morning, you increase the venting, less dissolved oxygen is in the water, and by the end of your shift, you notice the sulfite levels are climbing beyond set points. That’s why you have to turn down the sulfite pumps. When Tony gets in, he turns down the venting, more dissolved oxygen makes it through to the boiler, and sulfite levels drop by the end of his shift. That’s when Tony turns the sulfite pumps back up. It’s as predictable as Old Faithful,” said Detective H2O.

“That makes all the sense in the world, Ox. Tony ain’t going to take this well. I can’t wait to tell him. You got time to talk to the bosses?”

“Let’s go,” replied Detective H2O.

At an impromptu meeting over coffee and donuts, the water detective laid out what Max and he had just discussed. The bosses listened and nodded, knowing the credentials of Detective H2O were impeccable. With decades of experience and licensed as a Professional Engineer and Certified Water Technologist, when Detective H2O spoke, people listened.

At the end of the meeting, one of the bosses inquired, “There’s a big difference between the 15 to 33 inches of plume you mentioned, Ox. How do you know what the truly correct setting for the deaerator is?”

“That’s a good question you have there. The exact venting requirements may fluctuate as incoming water temperature and dissolved gas content change with the seasons. Plus, the deaerator can change as well with jumbled trays and changes in makeup demand and percent condensate return. There are many variables that come into play. But as a starting point, and to answer your question, what we can do is a dissolved oxygen study on the deaerator. Deaerator manufacturers design for removing oxygen to as a low as 7 parts per billion. Practical experience has shown a more realistic number may be as high as 24 or 40 ppb, depending upon the deaerator design. We’ll need to turn off the sulfite feed and give it sufficient time to flush through the deaerator storage tank. Then we can take a tap off the feedwater line and test dissolved oxygen. It’s not an easy test, and the test procedure must be performed nearly perfectly, but this isn’t my first rodeo. Any testing I do will be a snapshot in time, of course, but we can take the system operating conditions into consideration.”

“That’s a good idea,” replied the boss. “Work with Melvin here to make the arrangements you need. I’ll post a memo so the shifts know we’re going to scientifically prove the venting requirements of the deaerator. No one can argue with that.”

* * *

Later that week, Detective H2O was back at the Acme Frisbee Company early in the morning to perform the dissolved oxygen study on the sulfite-free deaerator. Starting at the wisp of steam that Tony liked, they incrementally increased the venting until the dissolved oxygen content stabilized. Detective H2O studiously graphed the results detailing operating conditions at each data point. By the time they were done, they had a complete profile of the deaerator’s oxygen removal capabilities for that day. The deaerator did a good job removing dissolved oxygen when vented properly, down to 15 ppb when the plume was in the 20-25 inch range with a quarter-inch invisible area above the vent.

“Now, these are not exact numbers written in stone. Like I said, there are several factors that can influence the efficiency of a deaerators, but they do show the impact of too little venting. Not only does the sulfite feedrate increase, as you’ve seen, but the risk for corrosion also increases. Yes, some steam is lost in the process, but the money you save by protecting your boiler system from corrosion far outweighs this,” Detective H2O told Melvin and the bosses.

“You’ve done it again, Ox,” enthused Melvin. “I can’t wait to tell Tony…”

“Why don’t you let me tell Tony. I’ll bring donuts,” smirked Detective H2O.

* * *

In the underbelly and penthouses of the metropolis of Waterville, where the boilers percolate and cooling towers fog, there is one man who works tirelessly to end corrosion, stop scale, fight lowlife microbes, and conserve water. That man is Detective H2O. Best water treater this side of the Ohio. Solving water problems drop by drop.