Editor’s Note: It has been said that most pharmaceutical companies fail to capture and use more than 10% of the information coming from the instruments already installed in their manufacturing plants. This information could facilitate equipment troubleshooting and trending and improve overall process control, alerting operators to upcoming equipment failures before multi-million-dollar batches are destroyed. In the past, a major drawback has been the cabling required for controlling instrumentation at the field level.
Now, some manufacturers are turning to fieldbus communications systems to connect sensors, actuators and control elements so that process control can be distributed across a Local Area Network, and processes controlled at the field level.
Fieldbus standards took decades to take shape, and “warring” protocols are out there, including Foundation fieldbus, Profibus, AS-interface (AS-i) and DeviceNet, each with its own unique strengths. Rather than choose one or another, Genzyme used four different fieldbus protocols in a multi-fieldbus control system at one of its biopharma facilities in Massachusetts, reducing cabling requirements and improving maintenance. Taking advantage of new equipment diagnostics, the installation is expected to eliminate waste that might otherwise result from undetected maintenance needs and equipment failure. Such waste would be even less tolerable at this Genzyme facility, given that the products at stake are orphan drugs, critical therapies with small markets, and the only treatments available for some rare diseases.
This two-part article, adapted from an article previously published in our sister publication, Control magazine, examines how Genzyme went about choosing and implementing fieldbus protocols and technology, and adapting them to the unique needs of a biopharma manufacturing plant. Could fieldbus be right for your facility? See the checklist below (Is Fieldbus Right for You?) to find out.
GENZYME CORP. RECENTLY INSTALLED a multiple-fieldbus control system platform at its 12-year-old pharmaceutical manufacturing facility in Allston, Mass. (see Optimizing Manufacture of Orphan Drugs, below) The new control system is used exclusively in a manufacturing suite that produces Myozyme, a drug that is used to treat Pompe’s disease, often fatal in young children. The condition is caused by a defective gene for the acid maltase enzyme, which affects the storage of glycogen in the body.
Fieldbus is used in process areas, electrically rated as “general purpose” and “Class 1, Division 2.” Process areas included in the multi-bus control system include mammalian cell culture, purification, clean-in-place (CIP) and steam-in-place (SIP). Bus technology has been deployed on skid equipment, which includes bioreactor skids, chromatography skids, ultra-filtration skids and CIP skids. Bus technology has also been stationed on stick-built fixed vessels, associated piping and transfer panels. Fieldbus protocols included in the facility are Foundation fieldbus, Profibus-DP, AS-interface (AS-i), and DeviceNet.
Baptism by Fire?
This project was our introduction to bus technology at Genzyme. We selected fieldbus technologies based on process equipment needs in a cell culture and protein purification manufacturing environment.
We knew that fieldbus instrumentation would be more expensive to install than the alternatives, but we felt that it could reduce controller cabinet size, cable count and conduit sizes and quantity. However, we believe that our biggest savings are still yet to come with the predictive maintenance model inherent in the Foundation fieldbus protocol. Foundation fieldbus transmits device status along with the process variable, allowing one to receive information on device health and warnings of impending failures. In biopharma, this can mean the difference between a successful multi-day or month batch run and a failure resulting in millions of dollars worth of lost product.
This two-part article (part two will run in October’s issue) will summarize our experiences installing fieldbus control at this facility, and discuss the implications of fieldbus technology for facility constructability, software design, commissioning, metrology and calibration, validation and maintenance.
Which Fieldbus Where?
We selected DeltaV from Emerson Process Management as the host controller, primarily for its batch capabilities. DeltaV is fieldbus-ready for the following fieldbuses: Foundation fieldbus, Profibus-DP, AS-i and DeviceNet. The project’s total I/O count was approximately 4,000 points.
When we began the project in 2003, it was relatively easy to find fieldbus-enabled pressure, temperature, flow, pH, conductivity, level and modulating control valve applications.
At the time, though, we could not find fieldbus-enabled versions of some of the instruments critical to biopharma manufacturing processes: dissolved oxygen instrumentation, for example, used for in situ measurement in bioreactors, or vessel weight indicators (strain gauge type). In addition, UV analyzers for liquid chromatography weren’t available in fieldbus versions. In addition, mass-flow controllers, used extensively with bioreactor equipment, weren’t Foundation fieldbus ready, but were available with a Profibus-DP interface.
We overcame these obstacles by using 4-20 mA current-to-fieldbus converters for dissolved oxygen, vessel weight and UV analyzers, and using a Profibus interface for the mass-flow controllers.
ASi Eases Valve Control...in General Purpose Areas
Valve control for open/close valves and the discrete input devices used in the general purpose electrical environment could be easily addressed with the simple AS-i bit-bus. There were many opportunities for actuating rising-stem or quarter-turn valves, which are used primarily for sanitary diaphragm valves and quarter-turn ball valves. AS-i was also used for discrete input devices, such as valve limit switches and proximity switches found on process transfer panels.