This is part 1 of a 3-part series on automation on the food and beverage plant floor.
Automation, in the most fundamental sense, means using brains instead of brawn.
As it becomes more sophisticated, automation means giving machines their own “brains,” as well as the senses, muscles and underlying nervous system that allows automated decision-making to be carried out correctly, efficiently and repeatably.
Coordinating and controlling food and beverage plant operations, across both the plant floor and the entire enterprise, is the ultimate way to get the most out of automation. As operations technology (OT) increases in reach and sophistication, it gives the food industry the prospect of bringing performance to new heights.
“We went from islands of information and machines doing their thing and nobody talking to anybody else, to the next level where they said you know, I wish I could figure out why my lines aren’t running the way they’re supposed to be running,” says Tim Gellner, senior consultant in the operational consulting group at Maverick Technologies, a Rockwell Automation company.
“And that led to more and more integration and data collection, and now with manufacturers moving quickly toward data-driven decision making fueled by advanced analytics, those who have not started down the path are finding that if they don’t keep up, they’re not going to be competitive.”
Climbing the stairs
Like most complicated endeavors, the OT that supports automation, and that enables it to coordinate with higher business functions, usually gets built in steps, or layers. Getting the most out of automation is a matter of ascending these steps.
The most basic level of automation relies on hard-wired analogue signals from sensors, valves and other field devices to input/output (I/O) modules. These do the work of converting these analogue electrical signals into the digital language of a computer or programmable logic controller (PLC) – and back again.
An analogue input and output signal may switch on and off to indicate process status (i.e., whether a valve is open or closed), or vary continuously in voltage or current to indicate a process variable (e.g., a temperature in an oven or level in a tank). Most analogue field transmitters use a current varying from 4 to 20 milliamps (4-20mA) to indicate the value of a process variable within a specified range, or to instruct a pump how fast to run.
And while hardwired analogue communications are both speedy and reliable, they’re relatively inflexible and typically communicate only a single piece of information—-a status, the value of a variable, or a simple command.
Concept Systems, an automaton contractor, estimates that 80% of the food and beverage plants it services rely on hardwired, analogue communications between its controllers and field devices.
“For years, food and beverage processing plants have relied on hardwired automation technology,” a Concept Systems spokesperson says. “Dependable, hardwired controls are good at executing exactly what is required. But as food industry standards evolve, these traditional systems are stalling business objectives.”
Turning analogue into digital
Industry’s first efforts to piggyback more information onto the 4-20mA analogue loop were by superimposing a changing frequency pattern onto the base signal. This Morse code of sorts allowed field devices to communicate parameters pertaining to their own health status or maintenance needs back to the operator, or for the operator to remotely re-range a transmitter without sending a technician into the field. This approach to enhanced field device communication was standardized in the 1980s as the HART protocol, and is still widely used today.
Escaping the architectural constraints of analogue wiring would require the full digitization of field device communications, and that arrived in the 1990s with the advent of “fieldbuses.” Simply put, a fieldbus is a digital network that allows multiple devices to be connected to a single network segment or loop. Data enters the loop at any point and travels to wherever it’s needed, hopping on and off the loop like it’s using a bus.
The most basic advantage of fieldbuses is that more information can be exchanged among controllers and field devices. They’re also a step forward in flexibility, since a new measurement device can be added to an existing network segment.
However, a fieldbus, like any network, can only link compatible components. This digital data needs to be in a consistent digital language. That means all the devices have to speak the same language, or communication protocol.
When field device networking was first taking hold in the 1990s, major suppliers of industrial control equipment either developed or adapted communication protocols for their own devices. Foundation Fieldbus (developed by a consortium of instrumentation suppliers) and Profibus PA (Siemens) emerged and remain the primary alternatives for the networking of process instruments. Meanwhile, a number of device-level networks focused on non-process applications also emerged, including DeviceNet (Rockwell Automation), Profibus DP (Siemens) and others.
These are still widely used and are no longer proprietary, meaning they can be used by suppliers other than the original developers. The problem is that devices that use different protocols often are not compatible and can’t be connected to the same fieldbus.
But the field-level compatibility issue may soon be resolvable through the industrialized use of the same thing that makes IT computer networks of all kinds possible: Ethernet.
Industrial Ethernet variants already are widely used one layer up from simple field devices, primarily for communication among PLCs, industrial PCs and other more complex systems. Here, Profinet and EtherNet/IP and HART-IP are among the protocol adaptations for standard Ethernet.
“If we can convince them to do Ethernet, that is the preferred method,” says Michael McEnery, president of McEnery Automation. The ultimate expression of IT/OT convergence, Ethernet continues to make inroads on plant floor, and work toward a single, unified network technology that spans from digital pressure transmitter to enterprise IT system is underway.
Keith Larson, group publisher and vice president for content at Putman Media, contributed to this article.