Connecting and controlling in food processing
14 June 2011
To help improve productivity and quality control, many food and beverage operations are now integrating their myriad operations and making them conform to automation standards, says Hector Lin, Industrial Automation Group at Advantech Corporation.
One of the traditional problems encountered by the food and beverage manufacturing industry has been the heterogeneity of processes in the plant. For example, there are both discrete and continuous automation applications in receiving, warehousing raw materials, and getting the raw materials to the process. Processes can be batch, continuous, or a hybrid of the two.
Take, for example, a simple brewery operation. Raw materials include hops, barley malt, flavorings and pure water. Each must be handled differently. The hops and barley malt are solids, and are handled by solids handling equipment such as hoppers, pneumatic or vacuum flow systems, and belt and bucket conveyors. Water and other liquid flavorings are handled in conventional liquid flow pipelines. Beer is made in batch kettles, so there are batch control steps including developing a recipe and programming the recipe, and then following the steps in the recipe, that can include automated and manual steps. Finally, beer storage is handled like any other tank storage application, with pumps, controls, flow and level indication.
The packaging section of the brewery probably uses discrete machine control and packaging systems which pull bottles and cans and packing materials together, fill the bottles and cans with beer, inspect them for damage and found object debris and then put the bottles and cans in boxes and palletise them ready for onward delivery.
The needs of food processing plants can vary greatly, and so will the control requirements, even within a single plant. Since the advent of the Programmable Automation Controller (PAC) and the migration of Ethernet to the factory floor in the 1990s, there has been a trend toward producing control and automation products that can be used in a variety of applications throughout a food or beverage plant, rather than mixing and matching systems and vendors from one part of the plant to another. These products include I/O, controllers, HMIs and graphic control panels, machine vision systems and industrial networking products.
Islands of automation
In most food and beverage plants, each portion of the process is built by a machine builder, and is often furnished fully constructed on a skid. Even when the process is not skid-built, the machine builder provides controls as he sees fit. Sometimes this will include control panels made with hardwired lights, switches, and relays inside a NEMA 4 or NEMA 12 control panel. Sometimes the control panels are entirely different to similar function panels in other locations across the plant, requiring increased training needs for operators. This requires more training for operators, and in emergency situations can pose an increased safety hazard as an operator may be interfacing with a control panel that is unfamiliar.
However, with the latest generation of automation and communication tools, food and beverage plants could be able to eliminate many of these potential safety issues by implementing common user interfaces, common recipe and standards-based batch programming, and relying on standards-based industrial Ethernet networking for data collection and transfer.
Common graphical Interfaces
From the smallest Hand-Off-Auto station to the most complicated batch programming station, touchscreen LCDs are easy to mount, use and interface directly via Ethernet or serial interconnection with controllers and I/O and can offer a replacement to the huge variety of lights and switches used in existing control panels around the plant.
A touch panel computer, such as the Advantech TPC with a 3.5in display, could replace all the lights, buttons, relays, and wiring of an existing machine or process control panel, and is flexible enough to handle any control panel application on the plant floor.
These HMIs are embedded computers, complete with networking and sometimes serial interfaces for legacy machines and controllers. Using an HMI, libraries of faceplates, indicators, widgets and objects can be pulled together on an editing screen, replacing the sourcing, purchasing, pulling from inventory, kitting, assembling and testing procedure used with hardwired operator panels. Even a relatively complex batching procedure can be designed on an HMI panel in days, where the old procedure might take weeks. This can offer huge cost savings, and is a safety enhancement too as a common HMI interface only needs to be learned once by the operator.
HMIs are getting smaller, faster, smarter, and less costly, allowing them to be applied to more sophisticated control problems, and to do complex mathematics, log data, handle alarm management algorithms, producing sophisticated graphics in real-time.
HMI panels designed for use in food and beverage industries should be suited to use in a sanitary and sterile environment and should support a variety of setup styles, including panel mounting in a larger control cabinet, VESA mounting, conventional desk stand mounting and on mounting arms for wall or ceiling mounting.
Advantech can offer IP66, waterproof and dustproof, versions designed for operation anywhere in the food or beverage process facility. IP66 HMIs can survive hose sprays and wash downs, even with corrosive or caustic chemicals. The touch screen itself is durable in both an acid and alkaline environment, and is designed to withstand detergents and commercial cleaners. A standard feature in a modern HMI that is purpose-built for the food or beverage industries is a “touch clean mode” where the touchscreen is capable of being disabled during the cleaning process with a special gesture. This avoids accidental touches while cleaning…a significant safety feature.
Another important design feature of a purpose-built food and beverage HMI or control system is the use of proper sanitary design in the enclosure usually to FDA requirements.
Common I/O and controls
The IPPC, TPC and UNO devices from Advantech are examples of combined HMI/PAC devices that can be used to display and control processes. In many applications, the HMI is primarily used to display information from the PAC and the other embedded PC controllers on the factory floor.
In the early 2000s, Craig Resnick of ARC Advisory Group gave a name to industrial computers re-packaged in a design that was very similar in form factor to the conventional PLC. He called them Programmable Automation Controllers, or PACs. Resnick’s PAC combined the features of a PC-based industrial computer with the control capabilities of a typical PLC. He noted that a PAC should combine the reliability of a PLC with the computing power and commercial off-the-shelf (COTS) operating system and software capabilities of the PC.
The Advantech APAX demonstrates the advantages of a modern PAC system. It integrates control, information processing and networking in a single platform.
Moreover, by utilising the dual-core multiprocessor architecture of the modern PC into automation technology, the system architecture provides dual controllers for different tasks, the same I/O with different controllers, and flexible I/O expansion with changeable controllers, reducing installation time and expense and integration complexity.
The modern PAC is a unitised platform that supports all of the control requirements across the processing facility. PACs are capable of operating as a complete, complex computing node in a distributed network, and as such, have succeeded in blurring the line between programmable control devices and higher functioning devices such as DCS field controllers and SCADA RTUs.
A typical PAC now provides:
* Multi-domain functionality, including logic, continuous and motion control on a single platform.
* Open, modular architectures with de-facto standards for network interfaces or protocols
* Single multi-discipline development platform that incorporates common tagging and a single database.
* Software tools that allow the design by process flow across several machines or process units.
A PAC that is purpose-built for the food and beverage industry needs to support digital and discrete I/O, as well as analog I/O for flow, level, temperature, pressure, and has to have voltage (0-5 VDC), current (4-20 mADC) and low frequency (pulse) analog inputs. These inputs would be essentially useless unless the PAC also has a sophisticated built-in PID control algorithm.
Early PLCs were primarily designed for discrete inputs. The development of multiple types of I/O and the Sequential Function Chart language of the IEC61131-3 standard, and especially the development of ISA88 made it possible to turn a PAC into a complete batching controller, running recipes, step charts and sequential functions in the field. Because PACs are easily networked, using standard industrial Ethernet, it is possible to extend the advantages of distributed control to a variety of continuous, batch, and discrete processes using the same computing platform.
Motion and inspection
The same PAC can also be used as a fast motion controller, for use in area such as packaging lines. Complex labeling and packaging applications can be controlled by the same computing platform that controls, for example, the brewery’s kettles, and can be programmed using the same programming tools and engineering libraries. The same high speed that makes fast motion control possible also makes the PAC suitable for use in for vision systems and video inspection applications.
Common networking and comms
Because PACs are purpose-built versions of PCs, they share the on-board capabilities of networking over standard networks such as Ethernet with their desk-mounted cousins. Most PACs have integrated capabilities for the standard network interface protocols such as TCP/IP, SMTP, and OPC. PACs can integrate multiple legacy industrial field networks, such as Modbus, RS232/422, RS485, CANbus, DeviceNet, Profibus, Foundation Fieldbus and others, over standard Ethernet networks, either wired or wireless.
The future of control in the food and beverage industries will require linking the HMI with modular I/O, robust computing platforms like PACs and embedded PCs with a complete industrial Ethernet product offering including managed switches, Power-over-Ethernet, and a common set of engineering tools.
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