VESSELS / VALVES
Designed to provide the maximum capacity with the lowest ocean shipping cost.
The cAT is an induced draft, counterflow design cooling tower with a capacity range of 173 to 472 nominal tons (762 to 2,079 kW). Standard construction consists of G-235 (Z-725 Europe) galvanized steel with type 304 or 316 stainless steel available for the basin or the entire tower.
cAT Cooling Towers - Design Features
The cAT Cooling Tower product line is an Advanced Technology design which utilizes induced draft counterflow technology -the most efficient in the industry and the best design for operation in a freezing climate. The counterflow design provides the cAT Cooling Tower with inherently better operational and maintenance features.
Principle of Operation
Warm water from the heat source is pumped to the water distribution system at the top of the tower. The water is distributed over the wet deck fill by means of large orifice nozzles. Simultaneously, air is drawn in through the air inlet louvers at the base of the tower and travels upward through the wet deck fill opposite the water flow. A small portion of the water is evaporated which removes the heat from the remaining water. The warm moist air is drawn to the top of the cooling tower by the fan and discharged to the atmosphere. The cooled water drains to the basin at the bottom of the tower and is returned to the heat source.
The vertical air discharge of the AT design and the distance between the discharge air and fresh air intakes, reduces the chance of air recirculation, since the warm humid air is directed up and away from the unit. For detailed layout information please consult EVAPCO's Equipment Layout Guidelines.
Efficient Drift Eliminators
An extremely efficient drift eliminator system is standard on the AT Cooling Tower. 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 AT Cooling Tower saves valuable water and water treatment chemicals. The AT 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.
The EVAPAK® Fill
EVAPAK® fill design used in the AT Cooling Tower is specially designed to induce highly turbulent mixing of the air and water for superior heat transfer. Special drainage tips allow high water loadings without excessive pressure drop. The fill is constructed of inert polyvinyl chloride, (PVC). It will not rot or decay and is formulated to withstand water temperatures of 130ºF (54,4ºC). Because of the unique way in which the crossfluted sheets are bonded together, and the bottom support of the fill section, the structural integrity of the fill is greatly enhanced, making the fill usable as a working platform. The fill selected for the Cooling Tower has excellent fire resistant qualities. Cooling Tower fill has a flame spread rating of 5 per ASTM-E84-81a. A higher temperature fill is available for water temperatures exceeding 130ºF (54,4ºC).
Superior Air Inlet Louver and Screen Design
The air inlet louver screens on the are constructed of corrosion-free PVC . They are a "Sight-Tight" two pass design that minimizes splashout and reduces the potential for algae formation inside the tower.
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.
EVAPCO's unique louver design completely encloses the basin area. Direct sunlight is blocked from the water inside the cooling tower, 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 cooling tower.
Reduced Piping Costs
Each cell of the AT Cooling Tower is furnished with one inlet and one outlet piping connection. This design reduces the amount of external piping and thereby lowers the installed cost of the cooling tower. The water distribution system is pressurized and self balancing. Since field balancing is not required on the AT, the need for flow balancing valves is eliminated, further reducing the cost of tower installation. The wide orifice nozzles with anti-sludge ring used in the AT water distribution system helps prevent clogging, reducing the maintenance costs of the water distribution system.
Pressurized Water Distribution System
The water distribution system is made of schedule 40 PVC pipe and ABS plastic water diffusers for corrosion protection in this key area. The piping is easily removable for cleaning. The water diffusers have a minimum opening of 3/8 by 1 inch (9,5 mm by 25,4 mm) and are practically impossible to clog. They also have an anti-sludge ring extending into the headers to prevent sediment from building up in the diffuser opening In addition, the spray branches have threaded end caps to allow easy debris removal.
The spray pressure for all AT Cooling Towers is between 1 and 6 psig (6,9 and 42 kPa) at the inlet header. The actual spray pressure will be shown on the certified drawings which are prepared for each unit.
Optimum Design for Freezing Climates
The counterflow fill design used in the AT Cooling Tower is well suited for winter operation. The wet deck surface is totally encased, and protected from freezing winds thus inhibiting ice formation on the fill section.
The even temperature gradient of the counterflow fill design makes the AT Cooling Tower the ideal unit for operation in freezing climates.
The counterflow design of the AT Cooling Tower fill section reduces the chance of ice formation and with bottom support, eliminates fill collapse should ice form.
Principle of Operation
Efficient Drift Eliminators
Superior Air Inlet Louver
Reduced Piping Costs
Pressurized Water Distribution
cAT Cooling Towers - Maintenance Features
Designed for easy maintenance, the cAT cooling tower leads the industry in service friendly features. The two most critical areas for cooling tower maintenance are the basin and the drive system. The cAT basin section is designed to allow quick and easy access from outside the cooling tower. Just like the basin, all service to the drive system can be safely performed from the side of the cooling tower. This eliminates the need to stand in the cold water basin or add costly fan deck handrails and safety cages for routine service to the bearings, belts, or electrical equipment. Evapco's Power-Band drive system is the easiest belt drive system to maintain in the industry!
The cold water basin section is easily accessible from ground level by simply removing the (2) two Quick Release Fasteners on the inlet louver assemblies surrounding the cooling tower and lifting out the lightweight louver.
The basin can be accessed from all (4) four sides of the cooling tower. The bottom of the fill section is a minimum of four (4) feet (1,2 m) above the basin floor. This open basin design enables the AT basin to be easily cleaned.
Stainless Steel Strainers
The EVAPCO standard for many years, the stainless steel strainer is one component of the cooling tower subject to excessive wear and corrosion. With stainless steel construction, this component will last the life of the cooling tower.
Easy, Removable Air Inlet Louvers with Quick Release Fasteners
The AT features a Quick Release Fastener design consisting of (2) two large thumbscrews and a latch system. By loosening the thumbscrews, the latch pulls up and out of the louver frame.
Clean Pan Basin Design
The AT features a sloped basin from the upper to lower pan section. This “Clean Pan” design allows the water to be completely drained from the basin. The cooling tower water will drain from the upper section to the depressed lower pan section where the dirt and debris can be easily flushed out through the drain. This design helps prevent buildup of sedimentary deposits, biological films and minimizes standing water.
Models cAT 17-49 through AT 17-912 Motor Mount, Power Band Belt Adjustment and Bearing Lubrication
The fan motor and drive assembly are designed to allow easy servicing of the motor and adjustment of the belt tension from the exterior of the unit. The T.E.F.C fan motor is mounted on the outside on these models and is protected from the weather by a cover which swings away for maintenance.
A large hinged access door is located on the side of the unit for easy access to the fan drive system. The belt can be adjusted by tightening the J-Bolts on the motor base and the tension can be checked easily through the access door, all while standing at the side of the unit. The bearings can also be lubricated from the side of the unit. The bearing lubrication lines have been extended to the exterior casing and are located by the access door, thus making bearing lubrication easy.
Stainless Steel Strainers
Removable Air Inlet
Clean Pan Basin Design
Motor Mount, Belt
cAT Cooling Towers - Drive Systems
The cAT Cooling Tower 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 cooling tower applications,
All AT Cooling Tower models utilize heavy duty totally enclosed (T.E.F.C.) fan motors designed specifically for cooling tower applications. In addition to the standard motors offered on each cooling tower, EVAPCO offers many optional motors to meet your specific needs, including:
•Premium Efficiency Motors
•Inverter-Duty Motors for VFD Applications
The T.E.F.C. motors are located on the outside of the unit and are protected by a hinged, swing away cover.
Fan Shaft Bearings
The fan shaft bearings on the AT cooling tower 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 cooling tower 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 cooling tower service, and is constructed of neoprene with polyester cords. The drive belt is sized for 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.
Fan Shaft Bearings
Power Band Belt Drive
Drive System Sheaves
cAT Cooling Towers - Optional Equipment
The standard design of the EVAPCO cAT provides the customer with the easiest cooling tower to maintain in the industry. There are additional options which can make maintenance easier and extend the life of the cooling tower. These options are listed below.
SECTION 23 65 00 - FACTORY-FABRICATED COOLING TOWERS
PART 1 - GENERAL
1.1 RELATED DOCUMENTS A. Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division 1 Specification Sections, apply to this section.
1.2 SUMMARY: A. This Section includes factory assembled and tested, open circuit, induced draft counterflow cooling tower.
1.3 SUBMITTALS A. General. Submit the following: 1. Certified drawings of the cooling tower, sound data, recommended steel support indicating weight loadings, wiring diagrams, installation instructions, operation and maintenance instructions, and thermal performance guarantee by the manufacturer.
1.4 QUALITY ASSURANCE A. Meet or Exceed energy efficiency per ASHRAE 90.1.
A. Motor/Drive System: Five (5) year comprehensive warranty against materials and workmanship including motor, fan, bearings, mechanical support, sheaves, bushings and belt.
B. Unit (cAT): One (1) year from start-up, not to exceed eighteen (18) months from shipment on the unit.
C. Unit (SST cAT): Five (5) year comprehensive warranty against materials and workmanship for complete unit.
PART 2 - PRODUCTS
A. Manufactures: Subject to compliance with requirements, provide cooling towers manufactured by one of the following: 1. EVAPCO, Inc. 2. Approved Substitute
A. Galvanized Sheet Steel complying with ASTM A 653/A 653M and having G-235 designation.
B. Optional Type 304 and/or 316 Stainless Steel as specified.
2.3 INDUCED-DRAFT, COUNTERFLOW COOLING TOWERS
A. Description: Factory assembled and tested, induced draft counterflow cooling tower complete with fill, fan, louvers, accessories, and rigging supports.
B. Cooling Tower Characteristics and Capacities: Refer to the Cooling Tower schedule.
C. Fan(s): 1. Type and Material (cAT): Axial propeller, individually adjustable wide chord blade extruded aluminum installed in a closely fitted cowl with venturi air inlet for maximum efficiency, covered with a heavy gauge hot dipped Galvanized fan guard. (optional Type 304 stainless steel) 2. Maximum sound pressure level of _____dB(A) measured at 5 feet above the fan discharge during full speed operation in accordance with CTI Standard ATC-128.
D. Water Distribution System: Non-corrosive materials. 1. Evenly distribute of water over fill material with pressurized spray tree. a. Pipes: Schedule 40 PVC, Non-corrosive Materials b. Nozzles: Non-clogging, ABS Plastic, threaded into branch piping. 2. Maximum pressure at inlet shall be ____ psig.
E. Collection Basin Material: Galvanized Steel (cAT - Type 304 Stainless Steel Optional) or Type 316 Stainless Steel (cAT):
1. Removable stainless-steel strainer with openings smaller than nozzle orifices.
2. Joints: Bolted and sealed watertight or welded.
3. Overflow, makeup and side drain connections
4. Flume plate between cells (for multiple-cell units) or Equalizer connection (for multiple-cooling-tower system).
F. Casing: Galvanized Steel (cAT) or Type 304 Stainless Steel (Type 316 Stainless Steel Optional):
1. Casing panels shall totally encase the fill media to protect the fill from damage due to direct atmospheric contact.
2. Fasteners: Corrosion resistance equal to or better than materials being fastened.
3. Joints: Sealed watertight.
4. Welded Connections: Continuous and watertight G. Fill Media: PVC; resistant to rot, decay and biological attack; formed, crossfluted bonded together for strength and durability in block format for easy removal and replacement; suitable for use as a working surface; self extinguishing with flame spread rating of 5 per ASTM E84-81a; able to withstand continuous operating temperature of 130�F; and fabricated, formed and installed by the manufacturer to ensure water breaks up into droplets.
H. Drift Eliminators: Same material as Fill. 0.001% drift rate.
I. Air Inlet Louver Screens: Formed PVC mounted in G-235 galvanized (or Type 316 stainless) steel frames for easy removal; designed "Sight Tight" to completely block direct sunlight from entering and water from splashing out of the cooling tower.
J. Water Level Control: Brass mechanical makeup water valve and plastic float with an adjustable linkage.
2.4 MOTORS AND DRIVES
A. General requirements for motors are specified in Division 15 Section "Motors".
B. Enclosure Type: TEFC
C. Motor Speed: Single Speed (Option: VFD Duty, 2-speed)
D. Drive: Power Band Belt designed for 150% of the motor nameplate HP.
1. Belt: Mutli-groove, solid back V-belt type neoprene reinforced with polyester cord.
2. Sheaves: Aluminum alloy if located inside the airstream.
3. Bearings: Heavy duty, self-aligning pillow block bearings with lubrication lines extended to side access door. Minimum L10 life for bearings shall be 75,000 hours. Provide extended grease lines and fittings.
4. Vibration Cutout Switch: Mechanical switch to de- energize fan motors if excessive vibration in NEMA 4 enclosure.
2.5 MAINTENANCE ACCESS
A. Internal Working / Service Platforms: Provide a complete internal working platform and ladder system for service of all drive components. A suitable working platform may be constructed of the fill media for counterflow cooling towers. If a crossflow tower is used, provide an internal walkway with ladder and elevated working platform to allow for service and maintenance to motor and drive assembly.
B. Handrails/Grabrails: Galvanized steel pipe complying with 29 CFR 1910.23. If access to fan deck is required, supply a perimeter handrail with ladder from grade to fan deck. C. Ladders: Aluminum, sloped "ships type" with grabrail or vertical complying with 29 CFR 1910.27.