Cooling Water System for DVD Production
Cinram, maker of pre-recorded DVD, VHS videocassettes, audio CDs, CD-ROMs and audiocassettes, acquired a videocassette plant in Ipswich, Suffolk, northeast of London. Two production lines were set up so the facility could switch to DVD production. About 10 months later another four lines were installed.
The key element is the machine in each line that forms the discs from polycarbonate raw material. Each machine contains a hot mold that must be a constant 203oF (95oC). Part of the mold temperature control system is the circulation of cooling water through channels in the molds.
The pumping setup of the first two lines had significant downtime -- a total of about one month out of 14 -- mainly because of water contaminated by ferrous oxide, said Kevin Steward, the plant's cleanroom engineer. The contamination accumulated on the piping's inner walls, reducing flow and cooling efficiency. Deposits also clogged mold water-channels.
For the four new production lines, Essex, U.K.-based company Air Options and Lowara UK designed and installed a cooling water pumping system that eliminated the problems of the first two lines.
The new systems consist of four closed-loop circuits separating the client and chiller processes by a series of plate heat exchangers. There are three identical water chillers, each containing a 184.9 gal buffer tank and pump set engineered to offer duty rotation and 100 percent redundancy via interface with the Lowara Hydrovar assemblies. To minimize contamination, the cooling water serves the process through a 6" dia ABS, reducing down to 2". To ensure correct and uniform return-water temperature at the pump sets, a 660-gal mixing tank was installed along with a water purification plant.
To further reduce contamination possibilities, the new pumps are stainless steel with silicon carbide seal faces, rather than the cast iron with carbon ceramic seals that make up the other pumps.
In addition, the pumps rely on Hydrovar, a variable-speed drive with preprogrammed software set up expressly for the centrifugal pumps. According to Steward, the software offers precise pressure control in the cooling water system. The Hydrovar pumps should produce a 30 percent to 50 percent energy reduction to pay for themselves within a year.