HVAC System

Cooling tower corrosion concerns cured

Source: PlantServices.com

Mar 30, 2006

Cameron Elastomer Technology (CET), Katy, Texas, provides engineered solutions to elastomeric material problems in the petroleum production industry. The 88,000-sq. ft. plant supports Cameron's elastomeric components and develops new products to meet stringent operating and environmental conditions. Products include ram packers, top seals and wellhead compression seals.

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CET had been operating a closed-circuit, single-cell, “all-in-one” fluid cooler with steel serpentine tubes at the top of the unit, a PVC water distribution system, PVC drift eliminators and TEFC centrifugal fan and sump pump motors. This cooling tower configuration can be difficult to service and impossible to expand if load increases.

At CET, the cooled water supply is either fresh or deionized (DI) water. The flow rate on both sides is 275 gpm with a 10° F [delta]T on the DI water side. Cooling tower water moves from the sump to the top of the tower, where it flows over the tubes to cool the DI water inside. The tower water is cooled and recirculated.

Cooling tower water can destroy metal components. The water is open to the atmosphere, so it can become contaminated with particulates and dissolved gases. Because it’s warm, it promotes growth of microflora. These contaminants, unless treated and removed, become corrosive and cause plugging.

Sooner or later, the cooling tower heat exchange surfaces will require overhaul or fail, resulting in intermixing of cooling tower water with the cooled water supply feeding expensive chillers, injection molding cooling circuits and process equipment.

It can be economically attractive to place a heat exchanger between the cooling load and the cooling tower. This isolates the expensive heat exchange equipment from the low-grade cooling tower water in the event of a tube leak.

CET’s unit needed repairs several times to correct corrosion of the housing and the galvanized metal tower. Access to the serpentine tubes in the tower was limited, making eventual tube repairs difficult.

Tranter PHE (www.tranterphe.com) replaced the existing tower with a combination plate heat exchanger (PHE) and evaporative cooling tower system comprised of its Superchanger Model GXD-042-H-5-UP-103 and a Paragon Model T-100I cooling tower from Delta (www.deltacooling.com). CET approved the Tranter PHE proposal based on the materials of construction:

  • Stainless steel PHE plates versus monolithic mild steel, bent-tube coil.
  • All-plastic HDPE cooling tower shell with 15 year warranty versus galvanized steel shell.
  • Other components made from PVC, aluminum and stainless steel.

CET also favored the PHE isolation system’s lower purchase cost and its flexibility, including the ability to upgrade capacity of both the exchanger and the cooling tower. The units also are easily cleaned and more efficient than shell-and-tube units because of their close temperature approach characteristics.

The isolation circuit is offering CET a higher measure of uptime security for its critical chillers and mold cooling circuits. The PHE is installed at ground level, so maintenance is easier compared to the top-mounted steel tubes in the former system. The isolation-circuit approach has proven to be the right one for CET’s cooling needs.