Fieldbus in biopharma applications, Part 2

ControlGlobal.com

Keywords: fieldbus, fieldbus control system, pharma, pharmaceutical processing and Genzyme

This article highlights issues associated with the installation of a multiple-fieldbus control system at a pharma processing facility and talks about its implications for handling an entire manufacturing suite.

By William T. Dolan, PE, Genzyme Corp.

Genzyme Corp. recently installed a multi-bus control system platform at its 12-year-old pharmaceutical facility in Allston, Mass., which manufactures enzyme replacement therapies for rare lysosomal storage disorders (LSDs). The facility originally used a conventional distributed control system to make two enzyme replacement therapies, while the multi-bus control system and new process equipment were installed recently in a renovated suite, which is used exclusively for manufacturing Myozyme, which is a drug therapy for Pompe’s disease.

ADVERTISEMENT Fieldbus in biopharma applications, Part 1

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, ultrafiltration skids and CIP skids. Also, bus technology has been deployed on stick-built fixed vessels, associated piping and transfer panels. Fieldbus technologies included in the facility are Foundation fieldbus (FF), Profibus-DP, AS-interface (AS-i), and Devicenet.

This was our first introduction to bus technology at Genzyme and our subsequent selection of bus technologies based on the process equipment needs within a cell culture and protein purification manufacturing environment. Bus technology is used in process areas electrically-rated general purpose and Class 1, Div. 2.

[“Fieldbus in Biopharma, Part 1,” Control, July ’06, focused on why Genzyme decided to use fieldbus, how and where it was deployed, and what architecture was used. Part 2 continues coverage of how Genzyme’s fieldbus segments were designed.]

More Segment Design
The buses selected for our facility included a powered bus and an unpowered bus. The powered buses include FF and AS-i, while the unpowered buses include Profibus-DP and DeviceNet. The goal was to have the stick-built process equipment, which included vessels, transfer panels and skid equipment, use an identical segment design. This allowed us to develop segment design standards that were followed by our engineering design contractor and the skid vendors.

In the third picture in Figure 1 below, you can see green-colored modules near the bottom of the panel. These are discrete I/O modules that are attached to the AS-i segment in this cabinet enclosure. Transfer panel proximity switches are hardwired from the transfer panel location to these modules.  There was a concern about not exceeding the AS-i bus segment length, and so the segment length was minimized by placing the I/O modules in the field termination box (FTB) and not at the individual transfer panels. Today, this may not be a concern because segment length is less restrictive with AS-i segment tuners, which didn’t exist when our project was implemented.

FIGURE: 1: FIELDBUS SEGMENT DESIGN

Segment design includes the following components: 1) host control system cabinet with the various fieldbus I/O cards along with their respective segment power supplies; 2) stick-built field termination boxes (FTBs) distributed in the process area; 3) interior view of typical FTB; and 4) interior view of typical skid FTB. (Click the image to open an enlarged PDF.)

	FIGURE 2: CIP CART
	Cleaning bioreactor units requires a portable valve cart to be manually hose connected to various process piping headers on the bioreactor.

It’s typical in biopharmaceutical facilities to use portable equipment for more than one process unit such as a bioreactor. These are associated with the clean-in-place (CIP) process, which requires manual setup with transfer panels and hoses to ready a process unit for cleaning. The cleaning process is highly automated with sequencing of various piping flow paths by manipulating open/close diaphragm valves. Cleaning bioreactor units requires a portable valve cart (See Figure 2) to be manually hose connected to various process piping headers on the bioreactor. This particular cart includes five automated diaphragm valves that are part of an AS-i segment. The cable is plugged into an M20 style receptacle at each bioreactor when the cart is in use. This two-wire connection to the bus facilitates the operation of these five valves, and the AS-i protocol immediately recognizes these valves by their unique addresses.  There is nothing else to do. It performs in the same manner as if it were conventionally wired. The single bus connection represents five discrete outputs for the valve actuator solenoids, and 10 discrete inputs for the open/close limits for each valve. If this weren’t a bus design, then potentially there would have been the need to wire 15 cable pairs or 30 conductors to a larger portable connector.