Ups and Downs of Taking the Bus—Part II

In this two-part series, Wyeth's Gary Forrest discusses the challenges and benefits of implementing fieldbus technologies at a new bioprocess development facility. The first part can be read in the Q2 issue of Industrial Networking or by visiting IndustrialNetworking.net/wyeth1 right now.

By Gary Forrest, PhD, Wyeth Research

Wyeth’s new bioprocess development facility in Pearl River, N.Y. was planned to include process development and manufacturing of high-value products from microbial fermentation. New equipment and full automation, through the use of a modern, integrated process control system, would permit batch automation in accordance with ISA’s S88 standard. And the fermenters would be equipped with instrumentation and controls that connected to the process control system via fieldbus technologies.

Wyeth elected to move the license for its existing Emerson Process Management DeltaV process control system and some of the process control system elements to the new building. A previous system upgrade had added fieldbus instrumentation and controls, and Wyeth specified fieldbus designs for the new plant, intended not only to replace existing facilities, but also to add new functionality.

Commissioning

System commissioning for this system was a multi-step process beginning with factory acceptance testing that took place from September through December 2003.

During this period, there was limited coordination between the fermentation equipment manufacturer and the automation supplier, and some configuration and wiring issues were identified. Resolution of these issues was deferred until installation and commissioning. The fermentation skids were shipped at the end of December and placed in storage awaiting the completion of building construction. Site installation, startup and commissioning of the fermentation skids began in August 2004.

Problems identified during fermentation-skid factory-acceptance testing needed to be resolved on-site. Although there were a few issues with FF devices, the fieldbus provided a solid communications platform with sophisticated interaction between the DeltaV process control system and the field devices. FF provided full digital communications and diagnostics for all devices without complex configuration or interpretation of signal bits (Figure 1).

Bus Transfer The temperature and pressure transmitters on biowaste vessels are FF devices. The digital I/O is based on a Festo Profibus-DP solution. But liquid level is measured by a 4-20 mA HART device unavailable in a fieldbus implementation. Source: WYETH

There were, however, problems with our specific implementation of Profibus-DP instrumentation and controls. Personnel experienced with the startup and commissioning of Profibus-DP fieldbus systems were not available. Eventually, the problems were traced to wiring problems such as improper connector and wire combinations. Specific wiring requirements were not well understood during system installation, and diagnostic tools for the analysis were not readily available.

In addition, the software configuration of each Profibus-DP device, through the use of a GSD configuration file provided by the instrument and controls vendor, required the complex specification of slots and signals that needed interpretation by software on a bit, byte or word basis.

The DeltaV process control system provided interaction with the Profibus-DP devices in a manner that generally was limited to setpoints, process variables and digital states. Despite specific individual difficulties, the Profibus-DP instrumentation has provided reliable, robust communications with the DeltaV process control system since completion of commissioning.

Software Synergies

Emerson, through its local representative, Control Associates, based the DeltaV software configuration on a vendor functional requirement specification (FRS) supplied by Sartorius BBI. The fermenters were placed into service for R&D applications in Q4 2004 (Figure 2). Because the facility was up and operating for R&D applications, Wyeth had the luxury of entering a software development prequalification period for the DeltaV process control system.

During this period, Wyeth created its own comprehensive FRS for all systems not included in the Sartorius vendor documentation. At the same time, these documents went through several modifications as the software was modified to conform to user requirements. The DeltaV process control system was ready for qualification in August 2005.

Controlled Skid Sartorius chose instrumentation and controls with Profibus-DP connectivity for its 400-liter working volume fermenter. Source: WYETH

System Qualification—Fieldbus I&C

Wyeth carried out the control system validation with the help of Valspec, a validation contractor in Royerston, Pa., that specializes in qualification of DeltaV systems. A validation plan was developed in accordance with the International Society for Pharmaceutical Engineering‘s Good Automated Manufacturing Practice (GAMP 4), which established the scope, strategy, deliverables and responsibilities for system qualification.