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.
By the Numbers
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.
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 Vortisand a 90% removal of particles less than 5 microns was achieved.
LASER PARTICLE ANALYSIS
|Size (Microns)||Total Counts/cc||Counts %|
|Start Up (prior Vortisand)|
|After 60 days (inlet)|
|After 60 days (outlet)|