The Challenges in Integrating a Process Control System with Skid-based Equipment: A Case Study

by Robert Patrick

Most projects involve the same questions and challenges regarding the integration of the Process Control System (PCS) with skid-based equipment. This case study examines two approaches to Process Control Systems integration. In the first, the skid vendors were responsible for all aspects of the design, development, documentation, and factory testing of the control system with the system integrator handling only integration of the skid after delivery on-site. With the second approach, the system integrator was involved from the outset, taking the lead role in the design and development of the operator interface, data collection, and reporting while providing guidance to develop the control software.

This case study was a facility expansion, executed in two phases over a period of three years at a cost of $120 million. The project included equipment typical to biotech facilities such as utility skids for Pure Water (PW), Water for Injection (WFI), and Clean Steam, as well as process equipment such as buffer preparation tanks, bioreactors, clean-in-place (CIP) skids and lyophilizers. Phase A consisted mainly of the addition of utilities in one of the new areas of the facility, while Phase B included additional utilities and the process equipment. Both approaches need to consider the following items during the planning phase of a project:

These questions should be addressed clearly in the User Requirements Specification (URS) for the PCS. The PCS URS should be provided to the skid vendors during the bidding process and agreed upon as part of the PO. The PCS requirements for this project included:

The equipment in the facility was categorized into three different types based on the amount of required integration with the PCS.

With the Type A Equipment, the PCS was used to monitor and control all functions of the equipment. The PLC code was provided by the equipment manufacturer, while the PCS systems integrator provided the SCADA. Type A equipment included the PW, WFI, Clean Steam, CIP, and Bioreactor skids.

In the Type B Equipment, the PCS system provided no control or monitoring except for remote alarm notification. Type B equipment included operations such as the Glassware Washer, Autoclave, Depyrogenation Oven, and Lyophilizer.

For Type C Equipment, the equipment vendor did not provide any controls. The PCS system was used to monitor and control all parameters for the equipment with the PCS systems integrator developing all control specifications for these items. Type C equipment included utility storage and distribution systems, buffer preparation tanks, and solution preparation tanks.

During Phase A of this project, the skid vendors were responsible for the PLC programming, screen generation, documentation (SDS, FAT, SAT), and testing. The PCS systems integrator was then responsible for the integration of the skid after delivery on-site. In reviewing Phase A, the following issues were identified with this approach:

In an effort to improve the process, Phase B used a different approach. The skid vendors were responsible for the control programming, provided input for SDS documentation development and assisted during the FAT execution. The PCS systems integrator provided core PLC logic modules to the skid vendors and was also responsible for screen development, data collection, reports, documentation (SDS, FAT, SAT), and test execution. The advantages to this approach included:

From continuous involvement on both phases of the project, the system integrator provided core PLC modules, standard screen development, document templates and test execution that met the customer's needs for consistent displays, central data collection, and site-wide security. The following lessons were learned and recommendations emerged:

Robert Patrick has been with Superior Controls in Seabrook, New Hampshire for over nine years, where he is employed as a Project Manager. He holds both a BS and MS in mechanical engineering and has 13 years of experience in the automation and controls industry, with an emphasis in biotechnology over the last seven years.




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