catwb closed circuit cooler EVAPCO distributed by Clark Johnson Co.

The cATWB is an induced draft, counterflow design closed circuit cooler with a capacity range of 1,080 to 5,015 MBH (316 to 1,470 kW). Standard construction includes the patented, high efficiency Thermal-Pak® Coil and G-235 (Z-725 Europe) galvanized steel casing and basin. Type 304 or 316 stainless steel construction is available for the basin or the entire unit. cATWB has been designed to deliver the maximum capacity and fit inside of a standard shipping container.

evapco distributed by Clark Johnson Co

   Design Features

     Maintenance Features

      Drive Systems

      Optional Equipment

        Unit Specifications

cATWB Closed Circuit Cooler - Design Feature


The cATWB Closed Circuit Cooler is an Advanced Technology, induced draft counterflow design closed circuit cooler featuring EVAPCO’s patented THERMAL-PAK® COIL – the most efficient in the industry. The counterflow design provides the cATWB Closed Circuit Cooler with inherently better operational and maintenance features.



Principle of Operation Evaporative Mode  The process fluid is circulated through the coil of the closed circuit cooler. Heat from the process fluid is dissipated through the coil tubes to the water cascading downward over the tubes. Simultaneously, air is drawn in through the air inlet louvers at the base of the cooler and travels upward over the coil opposite the water flow. A small portion of the water is evaporated which removes the heat. The warm moist air is drawn to the top of the closed circuit cooler by the fan and is discharged to the atmosphere. The remaining water falls to the sump at the bottom of the cooler where it is recirculated by the pump up through the water distribution system and back down over the coils.    Efficient Drift Eliminators An extremely efficient drift eliminator system is standard on the ATWB Closed Circuit Cooler. The system removes entrained water droplets from the air stream to limit the drift rate to less than 0.001% of the recirculating water rate. With a low drift rate, the ATWB Closed Circuit Cooler saves valuable water and water treatment chemicals. The ATWB Closed Circuit Cooler can be located in areas where minimum water carryover is critical, such as parking lots. The drift eliminators are constructed of an inert polyvinyl chloride (PVC) plastic material which effectively eliminates corrosion of these vital components. They are assembled in sections to facilitate easy removal for inspection of the water distribution system. Superior Air Inlet Louver and Screen Design   The air inlet louver screens on the cATWB are constructed of corrosion-free PVC. They are a two pass design that minimizes splashout and reduces the potential for algae formation inside the cooler. In single pass louver systems used by other manufacturers, circulating water droplets tend to splashout, especially when the fans are shut off. With the two pass louver system, the water droplets are captured on the inward sloping pass, minimizing splashout problems. This unique louver design completely encloses the basin area. Direct sunlight is blocked from the water inside the cooler, thereby reducing the potential of algae formation. Water treatment and maintenance costs are substantially reduced. While effectively containing the recirculating water and blocking sunlight, the louver design has a low pressure drop. The low pressure drop results in lower fan energy consumption, which reduces the operating costs of the cooler. Pressurized Water Distribution System  EVAPCO's Zero Maintenance ZMII® Spray Nozzle remains clogfree while providing even and constant water distribution for reliable, scale-free evaporative cooling under all operating conditions. The heavy duty nylon ZM® Spray nozzles have a 1-5/16" diameter opening and a 1-1/2" splash plate clearance. Furthermore, the fixed position ZM® nozzles are mounted in corrosion-free PVC water distribution pipes that have threaded end caps. Together, these elements combine to provide unequaled coil coverage and scale prevention, and make the industry's best performing non-corrosive, maintenance-free water distribution system.Thermal-Pak II Coil EVAPCO's Thermal-Pak® coils feature a patented design which assures maximum cooling capacity. The airflow through the coil is counter to the fluid flow, providing the most efficient heat transfer process. A special coil design is utilized to reduce the air pressure drop through the unit while maximizing tube surface area and increasing its heat transfer capabilities. The uniquely shaped tubes of the coil are staggered in the direction of airflow to obtain a high film coefficient. The coils are manufactured from high quality steel tubing following the most stringent quality control procedures. Each circuit is inspected to assure the material quality and then tested before being assembled into a coil. Finally, the assembled coil is pneumatically tested at 400 psig (2758 kPa) under water to ensure it is leak free. To protect the coil against corrosion, it is placed in a heavy steel frame and then the entire assembly is dipped in molten zinc (hot-dip galvanized) at a temperature of approximately 800°F (427ºC). Note: Closed circuit coolers should only be used on sealed, pressurized systems. Continual aeration of the water in an open system can cause corrosion inside the tubes of the cooler leading to premature failure.Principle of OperationEfficient DriftEliminatorsSuperior Air Inlet Louver and Screen DesignPressurized Water Distribution SystemThermal Pak II Coil



cATWB Closed Circuit Cooler - Maintenance Features


Designed for easy maintenance, the cATWB Closed Circuit Cooler leads the industry in service friendly features. The three most critical areas for closed circuit cooler maintenance are the basin, drive system, and coil. The cATWB basin section is designed to allow quick and easy access from outside the cooler. Just like the basin, all service to the drive system can be safely performed from the side of the cooler, and EVAPCO's Power-Band drive system is the easiest belt drive system to maintain in the industry!


cATWB Closed Circuit Cooler - Drive Systems


The cATWB Closed Circuit Cooler features the highly successful EVAPCO POWER-BAND Belt Drive System engineered for heavy-duty operation. The POWER-BAND Drive System has consistently provided trouble-free operation in the most severe duty closed circuit cooler applications.

  •     Fan Motors
  •     Fan Shaft Bearings
  •     Drive System Sheaves
  •     Power-Band Belt Drive


Fan Motors



All cATWB Closed Circuit Cooler models utilize heavy duty totally enclosed (T.E.F.C. or T.E.A.O) fan motors designed specifically for closed circuit cooler applications. In addition to the standard motors offered on each cooler, EVAPCO offers many optional motors to meet your specific needs, including:


  • Premium Efficiency Motors
  • Multi-Speed Motors
  •  Inverter-Duty Motors for VFD Applications


3', 4', 8.5' & 17' (0,9; 1,2; 2,6 & 5,2 m) wide ATWB models feature T.E.F.C. motors are located on the outside of the unit, protected by a hinged, swing away cover. 12' & 24' (3,7 & 7,3 m) wide ATWB models have T.E.A.O. motors located inside the fan section on a heavy duty motor base which swings to the outside for repair or removal.





Fan Shaft Bearings


The fan shaft bearings on the cATWB Closed Circuit Cooler are specially selected to provide long life, minimizing costly downtime. They are rated for an L-10 life of 75,000 to 135,000 hours, making them the heaviest duty pillow block bearing in the industry used for Closed Circuit Cooler duty.


Power-Band Belt Drive


The Power-Band drive is a solid-back multigroove belt system that has high lateral rigidity. The belt is designed for closed circuit cooler service, and is constructed of neoprene with polyester cords. The drive belt is sized for 150 percent of the motor nameplate horsepower ensuring long and trouble free operation.




Drive System Sheaves


Drive system sheaves located in the warm, moist atmosphere inside the cooling tower are constructed of an aluminum alloy. Those located externally are protected by a hinged cover.

cATWB Closed Circuit Cooler - Optional Equipment


The standard design of the EVAPCO cATWB


  •     Motor Davit
  •     Sloped Access Ladders
  •     Stainless Steel Water Touch Basin
  •     Extended Surface Coil
  •     Electric Heaters
  •     Electric Water Level Control
  •     Evapco Manufactured 304 Stainless Steel Coils
  •     Other Options

Unit Specification

cATWB Specification Sheet

Closed Circuit Coolers

cATWB Closed Circuit Coolers

Clark Johnson Company, Inc.       2016