The existing Extended Nip Press section was a hardwire relays/timer system. The pressure and temperature controllers were pneumatic loop controllers. The customer's CC pressure control loop had a single valve serving dual purposes; it is used as a pressure dump valve and also as a pressure control valve. The pressure control loop was used in several modes with some of the modes having a different process gains.
Columbia Automation Systems designed a control system that included redundant power supplies, controllers, and communication networks. CAS also supplied an HMI with permissive, alarm, and process screens which incorporated the customer's existing HMI.
The system included two UL listed enclosures built by CAS's panel shop which is UL 508 certified. The first enclosure, installed in the customer's rack room on the operating floor, holds the redundant controllers, redundant power supplies and a gateway communication rack. The second enclosure contains redundant fiber communication to the rack room controller and all of the systems discrete and analog I/O cards. This enclosure was installed in motor control center near the hydraulic units.
Control system enhancements included automating the start-up sequence, removing the shoe lift mode, first out alarming, expanded alarms, and permissive screens. The pressure controls were enhanced with smart transmitters, electronic valve positioners, correct filtering for process measurements, setpoint ramping, and gain selection. These were implemented to yield smooth pressure control for all of the process modes.
The control system was set-up and tested by simulating the customers press section using discrete and analog signals. A witness test was conducted at CAS Vancouver Washington's facility with customer representatives from engineering and maintenance. The system was demonstrated using different process conditions and customer requested changes were made in addition to several enhancements. After successful completion of the witness test, the system was shipped to the customer's site for installation.
The enclosures were mounted and preliminary wiring completed prior to a 3-day scheduled outage in which the complete system would need to be installed and verified. During the 3-day outage the old control system was removed and the new I/O and field instruments were wired. All I/O check-out was completed and the system's six hydraulic pumps and field instruments were tested prior to start-up. The pressure control loops were tuned by simulating the process prior to start-up. All systems were validated and the press was loaded and successfully ran the first time a sheet was put across the machine. No downtime was experienced during start-up due to the press upgrade. A great team effort between the customer and CAS is credited for the smooth and flawless start-up. This accomplishment proved the value of thorough testing and simulations.
Columbia Automation Systems remained on site for another few days doing minor program and HMI programming, operation training, and completing as built drawings for the customer. This on site presence ensured a smooth implementation and contributed to exceeding the customer's goals.
Contact Shelby Brinkley for more information.