The City of Houston has selected planning, engineering and program management firm Lockwood, Andrews & Newnam Inc. (LAN) to develop...
The citizens of Atlanta depend heavily on the Hemphill and Chattahoochee water treatment facilities. Without them, there would not be readily available sanitary water for cleaning, washing, drinking and other daily activities. Pending completion of a significant upgrade, these facilities rely on time-consuming manual operation, control and maintenance. To increase the efficiency and capacity of the two water treatment facilities, the city of Atlanta is installing an automated system that will provide greater capability and accuracy in meeting regulations while still using manpower for control and maintenance.
To implement the automated controls, the city of Atlanta is working with Control Instruments Inc., Smyrna, Ga. In order to house the sensitive electrical systems and electronic controls that will automate the two facilities, Control Instruments required customized enclosures that would withstand the harsh water treatment environment and fit the specific measurements required by the facilities’ floor plans. The company sought out Pentair Technical Products for Hoffman-brand enclosures modified to the specific dimensions needed.
“About 35% of the enclosures we are using are custom-made,” said Jonathan Mitchell, project engineer at Control Instruments.
In the Hemphill facility, the need for custom enclosures stemmed from specific space constraints. The facility includes three filter pipe galleries, with enclosures mounted at the catwalks in each gallery above a handrail. This setup features a clearance of slightly more than 48 in. between the handrail and the ceiling. Plus, the enclosures had to be 72 in. wide to fit the necessary components, which is beyond standard size.
Crowder Construction completed the installation of the enclosures. It was a challenging task due to the dimensional restrictions. Advanced planning was required to make certain that the enclosures could be mounted properly. Custom steel supports were mounted to the floor and ceiling to allow for proper mounting.
Along with these custom size requirements, the demanding environment had to be taken into consideration. The filter pipe gallery is located below ground—under the water filters—and requires a particularly robust material to withstand water damage. Fiberglass, a thermoset polyester material reinforced with glass fibers, demonstrates high-impact strength and rigidity, offering a cost-effective alternative to stainless steel for corrosive environments. Because it has an excellent resistance to moisture, fiberglass provides an ideal fit for water treatment facilities. While it is unusual for a fiberglass enclosure to meet these dimensions, a custom mold was made to accommodate the requirements.
A total of seven 48-by-72-by-25-in. wall-mount NEMA 4X fiberglass enclosures were used throughout the filter pipe gallery. Additionally, a total of 30 standard 24-by-24-by-12-in. wall-mount NEMA 4X fiberglass enclosures were mounted adjacent to each filter’s existing operation console, at both the Hemphill and Chattahoochee water treatment facilities. These house a local operator interface terminal and additional equipment to allow the filters to be operated remotely from a central location at each facility. Standard-size mild steel wall-mount enclosures also have been installed throughout the facilities for various automation functions, and free-stand and wall-mount stainless steel enclosures were used outdoors.
The Chattahoochee facility did not have the same height restrictions in the filter pipe gallery, but a floor grating allowed just 18 in. of depth for enclosures mounted to the floor. To accommodate this setup, enclosures were decreased in depth from the standard 25-in. size to 18 in. These enclosures also had to be 72 in. wide to fit the necessary components and required a customer mold for manufacturing.
Ratings & Timeline
Two of the enclosure models featured two-door designs, which include a center post onto which the two doors latch. A standard two-door enclosure features a solid, nonremovable center post, but a removable center post was desired for the water treatment facilities to allow for easier mounting of the back panel.
“Pentair Technical Products had to ensure that this center post was mounted so the doors could latch properly and ensure a tight seal,” Mitchell said. “This is very difficult but necessary to maintain the NEMA and UL 4X rating.”
The NEMA 4X rating ensures the enclosures provide a degree of protection against water, rain, sleet, snow, wind, dust and, most importantly for a water treatment plant, corrosion. The UL rating is significant because certification confirms that the required construction and performance tests have been completed and passed.
The ratings were maintained with the mix of accessories used with various enclosures. Shelves to hold maintenance laptops were mounted in most of the enclosures, and light kits allow easy component viewing. Heaters, fan/filter packages and thermostats are utilized to control the temperature, maintaining the integrity of sensitive electrical and electronic components.
While the entire project is still in the design phase, Control Instruments has released two of four panel packages that include 14 custom fiberglass enclosures. The project is scheduled to be completed by February 2011.