As one lighting products manufacturer discovered, a self-cleaning filtration system can reduce cooling water costs and deliver a rapid return on your investment

The Philips Lighting plant in Danville, Ky., was spending nearly $250,000 per year on water for process cooling operations.

The Philips Lighting plant in Danville, Ky., manufactures nearly 10 percent of all the glass bulbs used to make incandescent light bulbs throughout the world. The plant also makes borosilicate hard glass for spotlight lenses and reflectors, as well as lead glass parts used in the manufacture of fluorescent tubes.

Sand from a particular Tennessee mine is the main raw ingredient of the bulbs made at this plant. The furnaces must reach temperatures in excess of 4,000°F (2,204°C) to melt the sand. Other additives such as sodium oxide, dolomitic limestone, lead and boron are added to this molten silica to produce the three specific types of glass used at this location. Like many other companies with applications in the plastics, food processing, petrochemical and other industries, this facility needed cooling water for heat exchangers, instrumentation and process cooling jackets.

Many processing plants use enormous amounts of water for cooling. This facility had tried recycling water in the past but ran into great difficulties due to the amount of total suspended solids (TSS) in the water. Heat exchangers would plug, cooling jackets would clog with debris, and instruments used to detect the level of molten glass in furnaces would overheat when cooling water lines choked off. Production decreased, waste increased, and labor costs ran rampant.

The expedient answer was to use a one-pass potable water solution: the cooling water passed through the facility just one time before being released to the environment through a permitted discharge. However, when the cooling plan was implemented, purchased water consumption immediately doubled. Nearly $250,000 per year was being spent on water alone. Resident engineers began focusing on finding a less expensive solution.

Philips Lighting installed automatic self-cleaning screen filters in the pump house to remove sediment and suspended solids from cooling water drawn from the detention pond near the plant’s offsite discharge. The filtration system has saved the plant $10,000 per month in water costs.

After evaluating a number of alternatives, Tom Broderick, maintenance manager for Philips Lighting, selected automatic, self-cleaning screen filters to filter the cooling water prior to its introduction in the process equipment. The self-cleaning screen filters were installed in the pump house to remove sediment and suspended solids from cooling water drawn from the detention pond near the plant’s offsite discharge. This filtered, recycled water then was sent to the plant, at flow rates ranging from 800 to 1,800 gal/min, for use in cooling vacuum pumps and other onsite process applications.

Finding a filtration system that would fit in the pump house presented a challenge. Because the two vertical turbine pumps took up so much space in the pump house and forklift access to periodically pull these pumps was necessary, most filters could not fit. Broderick chose two Orival Model ORG-060-LS automatic filters for the job because they were vertically oriented and required little water flow for the self-cleaning process (see sidebar).

According to Broderick, the plant immediately began reaping benefits from installing the self-cleaning filtration systems.

“Our water bill has decreased by $10,000 per month since installing the Orival filters. Commercial laboratory analyses have shown TSS in the filtered water to be just as low as in our available potable water supply,” he said.

John Wynd, engineer-fellow, glass operations, said that he is ready to install filters in another application to cut municipal water consumption even more. The bottom line is that the filtration system has provided Philips with an extremely fast payback and a large yearly savings.

How the Self-Cleaning Filtration System Works

Dirty water enters the inlet, where it goes into the center of the cylindrical fine screen element. The water then passes through the fine screen from the inside out and exits the outlet. The unwanted solids accumulate on the inner surface of the fine screen, creating a pressure differential across the screen element.

Once the pressure differential reaches a preset value (normally 7 psi), the factory supplied control system opens the rinse valve to an atmospheric drain, and a rinse cycle is activated. As a result, the pressure drops in the hydraulic motor chamber and dirt collector assembly. The pressure drop causes water to backflush through the screen in an area the size of a dime (about 0.625") at the nozzle openings, which are located close to the inner screen surface. This high-velocity backflush stream pulls the dirt off the screen, similar to a vacuum cleaner. The backwash water is carried through the collector and ejected out of the holes in the hydraulic motor. The water being ejected out of the hydraulic motor causes the collector to rotate, similar to an old-style lawn sprinkler. In addition, pressure is released from the hydraulic piston located at the top of the filter, which causes the collector assembly to move upward.

This combination of rotational and linear movements ensures that the entire screen area is cleaned each cycle. The cleaning cycle of the smaller filters takes less than 10 sec and discharges as little as 3 gal per cleaning cycle, while larger filter models can take up to 15 sec to clean using about 11 gal of water.