PPG Industries will invest more than $23 million next year at its Meadville, PA, glass plant to rebuilt a melting tank and install energy-efficient oxygen-fuel firing technology on one of the facility's two float glass production lines. The float glass production line to be converted at Meadville will be shut down in the first quarter of 2002 for about three months during the tank repair, a normal periodic maintenance procedure. When the line is shut down, it will have operated 11.5 years and undergone nearly 100 product changes. The plant's other line is not scheduled for rebuild before 2005. According to the company, there will be a limited number of voluntary layoffs during part of the shutdown. The facility has about 400 employees.