Client Goal

Technical Goals

• Establish distributed, yet tightly integrated, control architecture
• Provide redundant HMI system with auto failover
• Provide “dead-PLC” process survival and recovery
• Integrate with other process monitoring equipment
  

Project Overview

Providing a new, deionized water system in support of increased Fab demand while maintaining ongoing production without interruption presented significant challenges in both design and implementation. Tegron delivered on both counts, with innovation in architecture, software development, and deployment.  The design of the DI water system segregated control into five areas: Makeup, Loop A, Loop B, Loop D, and Regeneration. Each functional area is controlled by a single PLC with a mix of local and distributed IO. Communication networks are divided into functional layers based on data and reliability requirements at each level.

The information (EtherNet) network provided communication between the HMI Scada and View nodes using redundant fiberoptic media. The peer-topeer (ControlNet) network, with its built-in redundancy, served PLC-to-PLC and PLC-to-HMI communications. The control (Remote I/O) network was chosen to service IO that extended beyond the local chassis including solenoid panels and RO train skids. This network segregation provided a natural allocation of traffic specific to each part of the overall control scheme, enhancing reliability and expandability. The software architecture applied object-oriented methodologies to achieve a tight integration across all layers of the control scheme. I/O management and data scaling, HMI tag structure, device services, and alarm management, to name a few, were all generated from a common database that described the system objects and behavior. This standardized the approach to common elements within the system.

With devices in the system applied as objects (pumps, valves, ROs, EDIs, etc.) and common control code implemented as services, the developer and the service staff alike were afforded a common programming and data interface from one functional area to the next.

Innovation in software automation tools provided consistent offline code configuration and generation which drove out variability while maintaining device naming conventions and description compliance as well as affording support for additional facility requirements.

The benefits from this approach were most evident during implementation, when operation-specific code changes became necessary, and the time to implement these changes was dramatically reduced. System software and hardware were designed specifically to provide “dead-PLC” operation. Through tight integration of PLC software and back-up controllers, the DI water system continued to run, even when all PLC processors were powered down. Upon power-up, each PLC seamlessly asserted control of PID loops and field equipment with zero impact on the Fab.

Onsite implementation during the continued operation of the Fab provided its own challenges. Device cutover and code functionality validation were carried out with meticulous attention to production requirements to ensure uninterrupted production during system start-up.

Scope of Supply

• CAD Documentation
• Commissioning & Start-up
• Control Panel Fabrication
• Electrical Construction Management
• Electrical Control Design
• Human Machine Interface Development
• PLC Software Development
• System Training
• Support Agreements
  

The Outcome

Production Benefits

• New DI system increases Fab capability
• System implementation while Fab remains online
• Redundancy and dead-PLC operations improves system robustness