HFL

1.0 Hybrid Closed Circuit Cooling Tower

1.0 General: Furnish and install ____factory assembled, forced draft, centrifugal fan, hybrid closed circuit cooling tower(s) with vertical air discharge, conforming in all aspects to the specifications and schedules as shown on the plans. Overall dimensions shall not exceed approximately ____mm long x ____mm wide x ____ mm high. The total connected fan kW shall not exceed ____kW. The total connected pump kW shall not exceed ____kW. The hybrid closed circuit cooling tower(s) shall be Baltimore Aircoil Model(s) ________________.

1.2. Thermal Capacity (water as heat transfer fluid): The hybrid closed-circuit cooling tower(s) shall be warranted by the manufacturer to cool ______lps of _______ water from ____°C to ____°C at ____°C entering wet-bulb temperature and from ____°C to ____°C at ____°C entering dry bulb temperature.

(Alternate 1.2.) Thermal Capacity (aqueous glycol solution as heat transfer fluid): The hybrid closed circuit cooling tower(s) shall be warranted by the manufacturer to cool ________lps of _____% by volume ethylene/propylene glycol solution from ______°C to _____°C at _____°C entering wet-bulb temperature and from ____°C to ____°C at ____°C entering dry bulb temperature. Coil pressure drop shall not exceed ________bar.

1.3. Corrosion Resistant Construction: Unless otherwise noted in this specification, all steel panels and structural members shall be constructed of heavy-gauge hot-dip galvanized steel, with all sheared edges given a protective coating of zinc-rich compound.

(Alternate 1.3.) Corrosion Resistant Construction: Unless otherwise noted in this specification, all steel panels and structural members shall be protected with the BALTIBOND®Corrosion Protection System. The system shall consist of hot-dip galvanized steel prepared in a four-step (clean, pre-treat, rinse, and dry) process with an electrostatically sprayed, thermosetting hybrid polymer fuse-bonded to the substrate during a thermally activated curing stage and monitored by a 23-step quality assurance program.

1.4. Quality Assurance: The hybrid closed circuit cooling tower manufacturer shall have a management system certified by an accredited registrar as complying with the requirements of ISO-9001 to ensure consistent quality of its products and services. Hybrid closed circuit cooling tower manufacturers that are not ISO-9001 certified shall provide an additional year of warranty to the customer at no additional cost.

1.5. Warranty: The manufacturer’s standard equipment warranty shall be for a period of not less than one year from date of startup or eighteen months from date of shipment, whichever occurs first.

2.0 Construction Details

2.1.Tower Structure: The hybrid closed circuit cooling tower shall be constructed of heavy-gauge steel utilizing double-brake flanges for maximum strength and rigidity and reliable sealing of water-tight joints. All sheared edges shall be protected with a coating of zinc-rich compound.

2.2. Casing Assembly: The hybrid closed circuit cooling tower shall include a coil casing section consisting of a serpentine coil, spray water distribution system, and drift eliminators, as indicated by the manufacturer. Drift eliminators shall be removable in easily handled sections. They shall incorporate a minimum of three changes in air direction.

2.3. Coil Assembly:

2.3.1. Prime Surface Coil: The cooling coil shall be fabricated of continuous lengths of all prime surface steel at the manufacturer’s own facility, and hot-dip galvanized after fabrication. The cooling coil shall be pneumatically tested at 10 bar. The cooling coil shall be designed for low pressure drop with sloping tubes for free drainage of fluid.

2.3.2. Finned Discharge Coil: The cooling coil shall be fabricated of copper tubes with corrugated aluminium plate fins and seamless copper tube headers with connections. The cooling coil shall be pneumatically tested at 10 bar. Fins with full drawn collars to maintain consistent fin spacing and a continuous surface contact over the entire tube. Staggered arrangement of minimum 4 circuits. Coils with heavy-duty aluminium frame shall be installed in a casing from galvanised steel. Casing includes an access plenum with access doors.

2.4. Water Distribution System: Water shall be distributed evenly over the coil at a minimum flow rate of 3.1 lps/m² to ensure complete wetting of the coil at all times by large-diameter, non-clog, plastic 360° distribution nozzles spaced across the coil face area in spray branches by snap-in rubber grommets, allowing quick removal of individual nozzles or complete branches for cleaning or flushing. Nozzles shall utilize a two-stage diffusion pattern to provide overlapping, umbrella spray patterns that create multiple intersection points with adjacent nozzles.

2.5. Spray Pump System: The hybrid closed circuit cooling tower shall include a close-coupled, bronze-fitted centrifugal pump equipped with a mechanical seal, mounted on the basin and piped to the suction strainer and water distribution system. It shall be installed so that it can be drained when the basin is drained. The pump assembly shall include a metering valve and bleed line to control the bleed rate from the pump discharge to the overflow connection. The pump motor shall be totally enclosed fan cooled (TEFC) type with IP 54 protection and class F insulation suitable for outdoor service,_____ kW, _______Volt, ________Hz, ______Phase.

2.6. Basin Assembly: The hybrid closed circuit cooling tower sump design includes a wet and a dry sump. During dry operation all water will drain from the dry sump into the wet sump, which is shielded from the airstream. Heaters in the wet sump are sufficiently sized to prevent freezing at temperatures as low as –25°C at full speed of the fan system.  Both sumps are compactly integrated into the design of the hybrid closed circuit cooling tower(s). The combination sump/fan section shall be constructed of heavy-gauge galvanized steel. The wet sump shall be provided with large area lift out strainers with perforated openings sized smaller than the water distribution nozzles and an anti-vortexing device to prevent air entrainment. The strainer and vortex device shall be constructed of the same material as the cold water basin to prevent dissimilar metal corrosion.

3.0 Mechanical Equipment

3.1. Fan System: The fans and motors shall be factory installed at the base of the unit in the dry entering air stream to provide greater reliability and ease of maintenance. The forwardly curved centrifugal fans shall be heavy-duty centrifugal flow types. Fan housings shall have curved inlet rings for efficient air entry and rectangular discharge cowls shall extend into the basin to increase fan efficiency and prevent water from entering the fans. Fans shall be mounted on a steel fan shaft supported by heavy-duty self-aligning, relubricatable ball bearings with cast iron housings and designed for a minimum L10 life of 40 000 hours (280 000 hrs average life). The fan shaft shall be protected with a two-part epoxy coating for corrosion protection.

3.2. Fan Motor/Drive System: Fan motor(s) shall be totally enclosed fan cooled (TEFC), IP-55, class F, selected for _____Pa static pressure. Fan motor(s) shall be suitable for _____ volts, ____ phase, ____ Hz electrical service and shall be mounted on an easily adjusted, heavy-duty motor base. V-belt drives and all moving parts are protected with removable screens.

(Alternate 3.2.) Baltiguard® Fan System: Two single speed fan motors, one sized for full speed and load, the other sized for 2/3 speed and approximately 1/3 of full load kW shall be provided in each cell for capacity control and standby protection from drive or motor failure. Two-speed motor(s) is not an acceptable alternative.

4.0 Access

4.1. Access Wet Sump: Large rectangular access door(s) shall be provided on the connection end of the cooling tower for access to the wet sump of the cooling tower, including water make-up valve, float ball and suction strainer.

4.2. Access Dry Sump: Circular access door(s) shall be provided for easy access to the air distribution plenum.

4.3. Acces Water Distribution System: Rectangular acces doors shall be provided in the plenum section under the finned coil for easy acces to the water distribution system.

5.0 Sound

5.1 Sound Level: To maintain the quality of the local environment, the maximum sound pressure levels (dB) measured 15 m from the cooling tower operating at full fan speed shall not exceed the sound levels detailed below.

Need more information? Contact your local BAC representative.