To reduce operations-crippling power sags, a production plant installs rotary power modules.

The Owens-Brockway bottle manufacturing plant runs around the clock, its four production lines producing more than two million bottles a day for Anheuser-Busch. But it only takes a brief power sag to alter operations — if not halt them altogether.

Electrical, hydraulic, and pneumatic systems power manufacturing processes at the Toano, Va., plant. Glass is heated by a furnace, then it travels through a refractory-lined tub and into an orifice that separates it into strands. These strands are cut into hot, molten globs that are gravity fed into molding machines.

During power sags, the glass globs continue to drop into the molding machine — even after it has stopped running. The glass cools quickly and hardens in the mold equipment, and employees must try to chip the glass out without damaging the mold. As a result, production grinds to a halt.

To deal with the sags, Plant Engineer Tom Cavaliero installed capacitor-based uninterruptible power supply (UPS) systems to protect the critical loads. While successful for a short time, the UPS systems did not provide the complete ride-through needed. At that point, Owens-Brockway contacted utilities provider Dominion Virginia Power. Dominion conducted an electrical survey, concentrating on the process power supply reliability, and then contacted power protection products manufacturer United Power Corp., Richmond, Va.

Two of the four production lines were tested and examined in detail. Stuart Carter, Southeast regional manager for United Power, proposed using a 30kVA rotary power module (RPM) as a cost-effective solution. It worked.

Using a motor-driven flywheel inertia system coupled to a generator, the load was isolated from the utility source, and the RPM eliminated all impulses. During the RPM's first year in operation, sags dropped from 20 to 11.

“It did exactly what we wanted it to do,” says Bill Jordan, technical advisor at Dominion Virginia Power. “We put it in full-time, but massaged our cost to keep it low. After this initial trial period, we were convinced it would do the job and then put in a second one.”

The second RPM (164kVA) was installed with the remaining set of bottle production machines the following year. This helped further reduce sags from 11 to four, and they were much less harmful than those in the past.

“One of the things we have noticed is that [sags] used to be a problem that started in the hot end where our bottle-forming machines are,” Cavaliero says. “Now the bottle-forming machines continue to run, so we've kept the main part of production — the hardest part — running.”