Brewing automation & data management; effective coordination and operations linkage in the planning stage can expedite brewhouse automation

Modern Brewery Age, Jan 22, 1990 by John Via

Brewing Automation & Data Management

The complexity of brewing operations makes the automation process a challenging combination of intelligent communication and effective coordination. In the early stages of automation, process control systems tend to evolve from the automation of stand-alone unit operations (brew kettles, fermenters, etc.) and typically have been designed to perform their function without the interaction of other systems. Subsequent attempts to integrate these "islands of automation" sometimes result in problems because of incompatible systems. This results from the failure to consider the needs and requirements of a fully integrated system. Accordingly, there is great incentive in the planning stage to provide the most effective coordination and linkages between operations, whether you are considering a full automation project or "staged" automation. The topics discussed in this article include the selection of field instrumentation and control systems, communications and integrated date management. The outline provided should be useful for managers and others involved in the planning and design of brewing automation projects.

Instrumentation and Control System

Selection

The control and data handling requirements for a project define the control system functionality. This is sometimes termed the "conceptual scope". Control system selection should be based on the needs and requirements of each project with consideration given for future expansion and integration.

Batch process control, which is common in the brewing industry, is characterized by the simultaneous manipulation of both analog and discrete variables based on a given batch sequence. The batch program defines the order of procedures, phases and steps required to produce a given recipe, and manipulates the required discrete devices and regulatory controllers.

The regulatory or analog control measures flows, pressures, temperature and other process variables, and adjusts final control devices (i.e. a control valve) to correct the error detected between the desired set point and measured variable. Analog inputs can be either 4-20 milliamps DC, 1-5 VDC or 1-10 VDC and are proportional to the measured variable (i.e. 0-100 gal./min.= 4-20 mA). Analog outputs are either 4-20 mA DC, or 1-5 VDC signals which are sent out from the controller to adjust the position of a final control device.

Discrete control, also known as digital or on/off, manipulates the positions of solenoid valves and start/stop switches, sensing position by switch closures from limit switches on valves, flow switches, pressure switches, temperature switches and proximity switches. Digital outputs are typically 120 VAC, 12 VDC or 24 VDC.

Field Instrumentation & Intelligent

Transmitters

The importance of instrument engineering is often overlooked in today's focus on Computer Integrated Manufacturing (CIM) and multi-level definitions of automation. Even the most sophisticated and fully integrated process control system is limited by the integrity and robustness of the sensors and final control devices. A steam control valve on a brew kettle with the wrong valve characteristics will operate just as poorly whether it is connected to a pneumatic or microprocessor-based controller. Proper instrument engineering is essential in any automation project, and its importance should not be underestimated.

Communications is also a key element in the overall structure of control systems. The process controller receives digital and analog inputs from sensors and analyzers which monitor the process and perform preconfigured operations. The controller then sends output digital and analog signals to equipment and control devices which manipulate the process. The process controller also coordinates operations involving the interaction between analog and digital control and handles sequential and data management functions. In addition, the controller also provides real-time communication to weigh scales, bindicators, analyzers and programable logic controllers.

It is important to recognize that the control system is part of a larger computer system which collects data from laboratories, barcode readers, PCs and other devices. The control system can be linked through an ancillary computer or device to access data from these devices. System design must be such that their communications do not interfere with the process control system, while the information is shared as required. For example, a bar-code reader is used to track raw materials usage by lot number. The information is used by the control system for batch reporting and the MRP II system for materials management.

The rapid reduction in the cost of microprocessors has resulted in the introduction of intelligent transmitters and sensors. As a result, many of the functions previously handled by the process control computer are now handled by the instrument itself. As an example, consider the intelligent flowmeter. Instead of the normal 4-20 mA output, the intelligent transmitter generates and transmits flow range, engineering units, sealing factors and configuration parameters. It is also capable of converting the analog flow rate to digital signal. Thus, there is a definite need for communications between the process controller and the intelligent transmitter, called a field bus. Currently, there is no industry standard for field bus communications and many vendors use their own protocols. The Instrument Society of America's SP-50 Committee is attempting to develop a standard communications protocol to resolve this problem.