Wrench time by design

Plant upgrades are opportunities to bring engineering and maintenance departments together.

By Mike Bacidore, chief editor

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Plant upgrades and overhauls mean involving the engineering department and having the foresight to not only change what is lacking, but plan for future needs, as well. Three plants took advantage of facility modifications and parlayed them into better maintenance and reliability.

In the first example, the addition of secondary wastewater treatment necessitated an upgrade in emergency standby power, which meant installing a new system that matched the existing one. The improvement allowed the treatment plant to meet EPA standards and gave it the backup power it required in the event of an outage.

Equipment stress protection made a difference in the second example, in which a firearm manufacturer increased reliability and productivity by implementing functional interface stress hardening. Engineering, operations, and maintenance personnel’s ability to work and plan together allowed the facility to mitigate equipment downtime.

Finally, when a food production plant had expanded to the point where it was unequipped to handle the breadth and volume of its products, a complete facility overhaul allowed for more efficient operations and the plant moved to a predictive maintenance strategy.

Stand by your power

Built in the late 1990s, the South Bay International Wastewater Treatment plant is a joint effort between Mexico and the United States to treat sewage from Tijuana, Mexico, and eliminate environmental concerns in the Tijuana River Valley just south of San Diego. The plant is located on a 75-acre site in the United States just north of Tijuana. The International Border and Water Commission (IBWC, www.ibwc.gov), the plant’s operator, needed to add secondary treatment to improve the quality of the discharge water.

The South Bay wastewater treatment plant has a capacity of 25 million gal/day. Its original design consisted of advanced primary treatment, which involved the addition of chemicals to the influent to promote removal of solids and dissolved organic compounds through settling. The treated water was then discharged via a 4.5-mile pipe extended out into the Pacific Ocean near the Mexico-California border. When the quality of the advanced primary treated discharge was found not to meet current environmental standards set by the EPA, the IBWC decided to add secondary treatment to the plant.

Secondary treatment involves bacteria-activated sludge combined with aeration and additional settling. Encouraged by the large supply of oxygen bubbled through the sewage, aerobic bacteria consume the remaining organic compounds in the effluent. The sludge is then removed by additional settling and then recycled to reuse the bacteria. After secondary treatment, the water quality is much improved and meets EPA standards. Adding secondary treatment has greatly increased the plant’s electrical load. The large aeration pumps and activated sludge system necessitated the addition of another 2,000 kW of emergency standby power, so the plant turned to MTU Onsite Energy (www.mtuonsiteenergy.com).

“The plant hasn’t been expanded in terms of overall capacity,” says Steve Smullen, area operations manager, IBWC. “It was originally designed for both advanced primary treatment and secondary treatment, but the secondary facilities were not immediately funded. Recently, we got the funding, and now we’ve added a biological system, aeration and settling facilities to meet our EPA permit requirements. As a consequence of completing the secondary treatment, we also added quite a bit of additional electrical load to the plant to operate three 700 hp aeration blowers and related equipment. In case of a utility outage, we needed the additional standby generation to handle those larger loads.”

Figure 1. The South Bay International Wastewater Treatment plant found a challenge in getting the two generators to fit into identical packages.
Figure 1. The South Bay International Wastewater Treatment plant found a challenge in getting the two generators to fit into identical packages.

The treatment plant wanted the new power system installation to physically match that of an existing 2,000 kW generator that was installed during the original construction in the late ’90s, says Tim Oergel of W.W. Williams, the local distributor for MTU Onsite Energy. “Getting the two generators to fit into identical packages was a challenge,” he says (Figure 1).

One design issue was that the MTU Onsite Energy unit was 16 years newer than its companion, which was from a different manufacturer. The new unit operates at 12.47 kV housed in a specially designed ISO container. This newer generator set is EPA-certified to meet Tier 2 emissions regulations, whereas the existing generator set was manufactured at the beginning of Tier requirements and was compliant with, but not EPA certified to, Tier 1 standards.

In addition to not having modern emissions control hardware, the existing generator drive engine set did not have an electronic governor or other electronic controls to help it synchronize with the new generator drive engine. To get the two generators to communicate with each other, the existing generator’s governor was replaced, along with many other controls. The overhaul also included new paralleling switchgear, automatic transfer switches, and various communications interfaces.

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