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 Case Study: The Vortisand® System Reduces Medical Center's Cooling Tower Operating Costs By Replacing Centrifugal Separators

 The Project

​The $500 million 434,000 square-foot, 6-story hospital building houses 262 beds and the adjacent medical office building is housed in a 172,000 square-foot, 6-story structure. In order to provide cooling and energy services to the campus, a 3-story, 31,800 square-foot central utility plant was included in the design.

The central utility plant includes three 3,000 GPM cooling towers and one 1,500 GPM cooling tower with the option to upgrade if needed. This hospital is located about 50 to 75  feet from a freeway with all 4 cooling towers facing the thoroughfare, exposing itself to the dusty air and debris. Being a hospital, it is run 24/7, with three 8 hour maintenance shifts.

With the need to filter contaminants from the water system, designers had originally specified centrifugal separators with bag filters as the side stream filtration technology. This technology works by separating particles from water using centrifugal energy and particle mass. The bag filters were used to filter small particles with the recovered water returned back to the system.

 The Challenge

​After a few months of operation a new challenge surfaced, maintenance costs were substantially increasing due to the cooling tower basins being cleaned on a weekly basis, along with the bag filters being replaced every shift due to the amount of dirt build up. Facilities Chief Engineer knew that this could not continue and embarked on a search for an efficient water treatment system.

J.D. Sales Co. presented Vortisand Cross-Flow Microsand Submicron Filtration as a possible water treatment system to resolve their dirt and debris related challenges. As particles smaller than 5 micron in size have been proven to be most likely to cause fouling and contamination in cooling tower systems, J.D. Sales Co. was confident that Vortisand was the correct technology for their side stream filtration project. Following this initial meeting, the customer was invited to visit a few existing installations that also used Vortisand systems for cooling tower side stream filtration. This included the new central utility plant at an international airport.

 The Solution

​As part of the evaluation process a total operating cost calculation was performed. It was clear that significant maintenance savings would be achieved by replacing the centrifugal separators with a Vortisand® system. Thanks to its compact design, the Vortisand systems were able to be installed on the existing concrete pedestals that were used for the outgoing separators. An added benefit to the Vortisand system is that basin sweeper piping was not needed and eliminated during the retrofit.

Upon start up, a laser particle analysis test was conducted, showing that particles of 5 micron and less in size made up over 95% of the particles within the cooling system water. After just 60 days of replacing the centrifugal separators with the Vortisand system a 90% removal of particles less than 5 microns was achieved.

 Cost Analysis

Energy Savings: $47,300
Maintenance Savings: $86,100
Estimated 1 year operating cost savings by replacing the centrifugal separator and bag filter with a Vortisand® cross-flow microsand filtration system: $129,720*

*Results may vary according to application and location. This TOC analysis is based on: (1) Backwash flowrate per tank. (2) Cost of water $0.0045 cents/gal. (2) Estimated additional cost of chemicals due to additional make up water required. (3) Cost of electricity: $0.15/kWh. (4) Observed replacement frequency. (5) Cost of labor $20/hr.

Download PDF version of the case study here.

 Performance of the Vortisand® System

In order to validate the performance of the new filters, water samples were taken at different stages of installation and LPA (Laser Particle Analysis) reports were done to determine the nature of the particles that were contaminating the cooling water system.

From the above data, it is clear that at the start-up of the Vortisand® units with 2 centrifugal separators in service, over 95% of the particles in the cooling system water were less than 5 micron in size. After just 60 days of replacing the centrifugal separators with Vortisand® cross-flow microsand submicron side stream filtration, a 90% removal of particles less than 5 microns was achieved.

“Over the last 6 months, I have to say that Vortisand® was the best investment on a filter system that we could make. It has cut down on not just particulate, but it has also cut down on man hours on the maintenance. We no longer have to clean bag filters and our new system keeps the basins a lot cleaner than ever before.” - Plant Operating Engineer

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