Heat Exchangers / Reliability & Maintenance

Energy Saver: Don’t Neglect Spring Cleaning Duties

A cooling tower’s rapid performance decline stemmed from a surprising culprit.

By Earl Clark, Energy Columnist

Rob and Jake started out their careers together. Rob was younger and attended night school while working as a designer with Jake during the day. Once he had his degree, Rob was transferred to one of the construction sites where he was the on-site project engineer. He and Jake maintained contact as they both moved from site to site and through a series of development assignments. Jake took an equipment specialist role and Rob moved into a field engineer role in Jake’s group.

Jake, the fouling is wiggling!

One day early in the spring, Rob called Jake, “I need your help. One of our chillers is losing performance quickly and we want to avoid taking it offline.” Rob described the problem. They had just started this chiller. It ran fine for a few weeks, but recently performance started declining. The performance loss escalated rapidly. Jake told Rob to start troubleshooting the problem per the course he had just taken. Rob checked the condenser flow rate and pressure drop. They seemed a bit high. He also ran a test on the heat exchanger for fouling. It was inconclusive.

Spring time usually was when “stuff” in the river water seemed to block condensers. So, Jake told Rob to take down the unit and open it up. It had lost so much capacity that it wasn’t helping with the plant cooling load anyway. Rob broke the news to upper management, who agreed to the additional work involved. Once opened, Jake expected the team would find a lot of vegetation blocking the tube sheet. Cleaning this would be easy, bringing the unit back online quickly.

Jake got a call from Rob later in the week. “Jake, the tubes are completely packed. And the fouling is wiggling!” Jake was speechless; he had never seen or heard of this. “Rod out some of the tubes and see what it is,” Jake advised. Rob called back later to say they discovered the identity of the fouling: eels, small ones from a spring hatch. Jake said, “Well that’s a first for me — you had me stumped for an explanation, but I will put that down in the experience book. Do you know how they got in there?”

Rob and Jake continued their investigation at the river pump house. The maintenance group opened the pump strainers and found damaged strainer elements. After replacing these, the pumps returned to service. All condensers were opened and rodded out, and chillers put back online. The problem chiller turned out to be the first one on the river water line — so it had collected more of the eels, enough to nearly block off all the flow. Once the condensers were cleaned, Rob conducted performance tests and registered a new baseline. He also added new maintenance guidance to the annual schedule so the plant would check the strainers during the spring timeframe.

So, have you checked out your cooling system this spring? Do you use river water? Springtime brings all sorts of “stuff” into the cooling water. Winter snow thaws and spring flooding picks up various plant material and dirt, some of which can get past even the best river water screens and strainers. Springtime also brings hatchings of marine animals, which also can end up in the river water intakes. Eels are not the only plant life affecting condensers. The spread of Asiatic clams has also resulted in springtime disasters in cooling systems. So, check and ensure your river water systems aren’t hiding a potential disaster.

River water systems are not alone in this regard. If you have cooling towers, it’s time to inspect and perhaps clean out the system. If the towers were offline, you could have algae growing in the fill and plugging the distribution basins and headers. Sometimes, wooden fill dries out, increasing mechanical failure as the dry rot can cause the fill to lose strength and fail when water passes over it. This, in turn, can result in blockage in the tower and condenser.

So, the time is now to do your checks. Happy energy savings hunting!

earl bionote imageEarl M. Clark, PE, – Engineering Manager, Global Energy Services. Clark retired from DuPont after a career of 39 years and 11 months and joined Hudson’s Global Energy Systems Group as Engineering Manager. During his over 43 years in the industry, he has worked in nearly all aspects of the energy field; building, operating and troubleshooting energy facilities for DuPont. He began his energy career with Duke Power and Clemson University during the energy crisis in the 1970s.

 Active in both, the American Society of Mechanical Engineers and the American Society of Heating, Ventilating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Clark was chairman of ASHRAE's task group on Halocarbon Emissions and served on the committee that created ASHRAE SPG3 - Guideline for Reducing Halocarbon Emissions. He has written numerous papers on CFC alternatives and retrofitting CFC chillers. He was awarded a U.S. patent on a method for reducing emissions from refrigeration equipment. He has served as technical resource for several others.

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