INTEGRATING BMS and PCS Systems in the GxP Environment

There are many ways to integrate building management and process control systems. One size does not fit all.
Feb 01, 2005
Volume 18, Issue 2

Multi-use, hybrid facilities are becoming the standard in the life sciences industry rather than the exception. Most facilities are designed to serve more than one purpose. While housing a manufacturing area may be a building's most important function, it may include a group of labs or warehousing space. These multi-purpose facilities create an interesting challenge. This article examines these challenges and potential solutions.

As an example, consider a facility with process and packaging lines, offices, a warehouse, some common spaces, and a cafeteria. The owner's challenge is to simultaneously manufacture the product, access and store the data, provide a comfortable environment, and comply with GxP regulations.

In theory, a single system can be used to accomplish these goals. Otherwise, the building management system (BMS) and the process control system (PCS) must be integrated. We will discuss the single-system scenario as well as five schemes for integrating BMS and PCS systems.

SINGLE SYSTEM The differences between BMS and PCS systems make it extremely challenging to integrate them into a single control system operating the process line and managing the environment. However, single systems are being explored and implemented with varying degrees of success. BMS is designed to control the heating, ventilation, and air conditioning (HVAC). It is "fit for purpose" with specialized algorithms and built-in functions specifically designed to streamline HVAC installation and operation. Other utilities are often controlled by the BMS but, BMS systems struggle with process control. They are not efficient in batch processes, and they are not designed for applications where sub-second sampling rates are required.

PCSs such as programmable logic controllers (PLCs) and distributed control systems (DCSs) are designed with process control in mind. They have software designed for controlling batch recipes, and they are equipped to handle high-scan-rate applications. However, it is difficult and costly to apply these systems to basic HVAC applications due to their hardware and software design.

For example, in office spaces, variable air volume (VAV) boxes provide conditioned air to each zone. The BMS has controllers with built-in flow transmitters and electric actuators that are designed to mount onto the VAV box's damper shaft in the plenum and control it based on temperature sensing in that zone. Additionally, the algorithms that control all the VAV applications are embedded in the controller and need only be selected in each application; no "programming" is required. This is a specialized, small point-count application that requires application-specific control to work effectively.

A PCS would struggle to handle this application efficiently and cost effectively. A PLC or multi-point controller is necessary, and a separate actuator would be needed for damper control. Ladder logic programming must be created to offer the appropriate control for the VAV box. Even if you find a ladder-logic programmer who understands this application, you will still lose the benefit of the specialized algorithms and functions already built into the BMS controller. The cost of the BMS application likely would be much less than the poorly adapted PCS solution.

Finally, there is the issue of validation. According to the current Good Automated Manufacturing Practices Guide (GAMP 4) of International Society for Pharmaceutical Engineering (ISPE), programmable controllers such as PLCs require Level 5 validation (the most stringent) since the code is untested. Most BMS controllers are configurable and require only Level 3-4 validation. The software objects are fully tested and only require configuration to make them application-specific. In short, one size does not fit all applications.

INTEGRATE TWO SYSTEMS VIA S95 As you can see, the differences between BMS and PCS systems make the single-system approach very difficult to implement. System integration is the most effective solution, allowing interaction and data passing between the two systems so they act more like a single system.

Facility integration often includes security and safety systems. Although these are outside the scope of this article, the concept of system integration still applies. In most cases, security and safety can be integrated into the BMS system, depending upon the owner's facility operation plan and requirements.

S95 is a standard developed by the Instrumentation, Systems, and Automation Society (ISA, http://www.isa.org/) to offer some consistency to the architectures and terminologies used in the automation industy.

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