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Waste of Money?

Dec. 1, 2011
The contractor was about to start installing new coils to replace coils that froze when the director of engineering called to go over my design.

The contractor was about to start installing new coils to replace coils that froze when the director of engineering called to go over my design.

"Why did you add those strainers?" he asked. "That's just extra cost for nothing."

"Well," I replied, "one possible reason the old coils might have frozen is that debris in the piping could have partially blocked water flow through the coils. There is a pretty long history of dirty water in this system. These are 100-percent-outside-air coils. If debris blocks one of the small tubes, the new coils could freeze, too."

"Waste of money," the engineer growled. "Maybe there were problems before I came here, but I know what I'm doing. I watch the water-treatment program and check the chemicals myself. I've got the system running clean now."

Because the general manager was nervous about another freeze-up, the strainers were installed. The day after the coils went online, I visited the site.

"Something funny is going on," the foreman said. "When I put the coils into operation yesterday, everything looked fine, but now the pressures are all out of whack, and we're getting hardly any heat from the coils."

After a quick look at the pressure gauges, I had a thought.

"Just out of curiosity," I said to the foreman, "could you pull out a couple of strainer baskets so I can take a look?"

The accompanying photos depict what I saw. That is about half of an inch of sludge that built up in about 24 hr of operation. If not for the strainers, the sludge would have been lining the insides of the tubes in the coil, where it would have impeded heat transfer and possibly blocked flow through some of the tubes.
Gary M. Elovitz, PE
Energy Economics Inc.
Newton, Mass.

Have a "war story" to share? Send it to Executive Editor Scott Arnold at [email protected].

About the Author

Scott Arnold | Executive Editor

Described by a colleague as "a cyborg ... requir(ing) virtually no sleep, no time off, and bland nourishment that can be consumed while at his desk" who was sent "back from the future not to terminate anyone, but with the prime directive 'to edit dry technical copy' in order to save the world at a later date," Scott Arnold joined the editorial staff of HPAC Engineering in 1999. Prior to that, he worked as an editor for daily newspapers and a specialty-publications company. He has a bachelor's degree in journalism from Kent State University.