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 LCFX system lowers system and energy costs and saves 80% in maintenance expenses

 Project

​A medical center in Georgia, USA made the determination that some type of filtration was needed for their three 400 ton cooling towers for the following reasons:

  1. Fouling and corrosion issues at the chiller condenser water head

  2. 1” of fine silt and organics sediment build up in the basins every 6 months resulting in:

    1. Two manual basin cleanings per year

    2. Legionella habitat buildup

  3. Cooling tower fill had to be replaced because of the fouling that had plugged the fill channels which resulted from the unfiltered cooling water.

  4. Towers had to be rebuilt after just eight years of operation because of the scaling and fouling issues that resulted from the absence of a filtration system.  

 Challenge

​Originally the medical center had specified sand media filtration for their cooling tower system. The objective was to clean the basins directly before any debris had a chance to enter the cooling system and to reduce the habitat for Legionella bacteria living in the deposits in the basin. After reviewing the media system with the mechanical engineering firm engaged to assist with the cooling tower renovation project, a decision was made to use automatic self-cleaning screen filtration technology for the following reasons:

 

  1. Limited space requirements. Media filtration systems would require one large media vessel per two cooling tower cells because of the backflushing methods inherent with this technology. Automatic screen filtration requires about half the footprint of media filtration for each tower.

  2. Unacceptable large amount of backflush water required by media filtration.  A fresh potable water supply, which had to be heat traced, was required to each vessel due to the backflushing methods inherent with this technology.  Each vessel had a filter rate of 57 m3/hr (251 gpm) and required a two minute 57 m3/hr (1,893 liters) or 251 gpm (500 gallons) backflush cycle for each backflush.  This large loss of potable backflush water required for backflushing was unacceptable.  

  3. Excessive energy requirements required for the proposed media system. The media filtration system required a 7.5HP pump for each two vessel system resulting in 22.5HP pumps running 24 hours per day. This would have resulted in a significant increase in the medical center's annual energy expense estimated at $19, 021 (assuming $0.11/kWh energy cost and best pump efficiency point of 85%).

After it was determined the media system was not a feasible solution, a screen filtration system was to be evaluated. Mechanical Products Inc. of Jasper, GA, requested that VAF be allowed to present its most recent LCFX cooling tower basin cleaning and water filtration system

 Solution

​Evoqua's VAF LCFX system was selected as the system of choice for the following reasons:

  1. Only one 10HP pump required to provide basin cleaning for the entire 1200 ton cooling tower.

  2. 55% reduction in pump size required by reducing from 22.5HP to 10HP.

  3. 70% reduction in filtration flow rate per tower basin from 159 m3/hr to 45 m3/hr (700 gpm to 200 gpm).

  4. 75% reduction in operating time from 24 hours per day to only 6 hours per day for all three towers resulting in total volume turned twice a day.

  5. 87% reduction in energy cost (energy cost for the LCFX-500-10 was $2,426.82 using a 74% efficiency and $0.11/kWh).

  6. 95% reduction in flush waste compared to a single tower media filter system.

  7. The footprint of the single LCFX system skid was 122 cm x 132 xm (48" x 52"), which was a much smaller footprint than for the two media systems option.  

  8. LCFX’s flexibility of basin cleaning times based on dirt load

  9. LCFX’s BACnet interface for remote monitoring and operation capabilities. 


 

LCFX General Operation

The LCFX system has unsurpassed conservation operating efficiencies over conventional cooling tower filtration systems while providing both basin agitation and cooling water cleaning.  By combining the patented V-SeriesTM filters and the reduction in energy usage and water saving components of the LCFX system, an ROI can be achieved in less than a year.  In addition, this system will help eliminate the environment where Legionella and other bacteria can grow by keeping the basins clean from organics and light silt that provide the habitat and food source for bacteria to thrive.

The zone control system maintains a pressurized mainline that has zone control valves placed at each defined zone.  Each zone has a specified number of eductor turbulator nozzles, placed inside the basin that agitates particulate and keeps it in suspension for removal by filtration.

The VFD/PLC control provides energy efficiency by operating the pump only at the minimum 1.4 bar (20 psi) required for the eductor nozzles’ basin agitation, and then provides the minimum of 2 bar (30 psi) required for the filter’s 30 second flush cycle, thus maintaining low energy usage for an extended time period.

For the medical center installation, the zone controller was initially programmed to monitor the cleaning of each tower for a minimum of two hours per tower per day.  This equated to a full turn of each basin volume twice a day in just six hours of operation.  The system then sleeps for the remaining 18 hours each day.

The extensive features and conservation benefits of the LCFX system provides the facility with clean cooling tower basins at a lower system cost, lower energy costs and saves 80% in maintenance expense.