Rendering Plant Keeps Running During Control System Upgrade
A rendering plant processing million of pounds of waste animal tissue per week needed a complete control system overhaul, with no downtime. Rendering converts waste tissue into stable value-added materials.
The plant works two shifts a day, accepting shipments from multiple processing plants. The fact was the animal tissue would arrive at the door whether or not the rendering plant was running. It had nowhere else to go. What’s more, spare parts for some of the control-system components in use were no longer available; the system had no redundancy or real-time reporting; and there was only one support person, stationed at a remote location.
The project participants agree that teamwork among plant, corporate, systems integrator, and electrical subcontractor personnel helped make the project a success. The upgrade included use of a modern information architecture, positioning the plant for greater use of information technology in the immediate future.
PLC I/O panel replacement
Today’s rendering plants need a reliable architecture that includes alarm and event data logging, and that delivers reporting needed for plant optimization.
Physically, the existing system included two four-door panels packed with nine vintage eight-slot racks and 64 I/O cards all controlled by a single processor. Two remote panels brought the system to 77 I/O cards. The cards themselves and the wiring were “vintage” and, having served well, were due for replacement.
Dallas-based I2R, a system integrator, contracted to supply all of the PLC I/O panels, programming and design, on-site electrical contractor supervision, and on-site start-up. The upgrades were divided into five sections, each to be installed during a weekend downtime window. Each window was from noon Saturday to 9 a.m. Monday morning—just 45 hours. The project manager was to conduct weekly conference calls with corporate and plant personnel.
It wasn’t possible to start by removing the old panels and installing the new ones. Instead, a nearby lab room was used to house the new panels, with pull boxes installed above them so that new wiring could be run to the plant floor from the panels. The technology employed included the following:
- Schneider Modicon Quantum fully redundant central processing units (CPU)
- Uninterruptible power supply (UPS) backup for each processor
- Wonderware ArchestrA system platform
- Redundant servers and network switches
I2R held a factory acceptance test four weeks prior to start-up and a software simulation three weeks prior. Operators and supervisors were able to interact with the system and ask questions, eliminating surprises and saving time.
New wiring and conduit were run while the plant was running. New conduit and single-conductor wiring replaced cable tray with tray cable. Once the new system was online, the old tray and tray cable were removed.
“The teamwork couldn’t have been better,” said the I2R project manager. “The plant worked very hard to give us the biggest downtime window they could. The contractors and software team were ready.”
Six start-up weekends had been planned, but that number was reduced to five because of the preparation work of the plant and contractor in prebuilding and testing motor control center (MCC) buckets. “The plant made the buckets available, saving time and money because the rebuilds were done on straight time rather than overtime,” the project manager said.
The upgrade has improved operations at the rendering plant, which has experienced no unplanned downtime in the three months following work completion. Remote support is online and development of business-intelligence dashboards is being planned.
Jerry Smith is president, Integrity Integration Resources (I2R), A Cates Company.