Industrial Controls: Demystifying SCADA
In a manufacturing setting, SCADA is the system of interconnected applications that controls everything from how the machines are programmed to the visual representation of the product as it makes its way through the machines, to the collection of data about the machines’ functionality, and more.
Supervisory control and data acquisition (SCADA) is the piece that ties all the intelligence of a manufacturing plant together, said Ken Crawford, director of automation at Weidmüller USA. “SCADA is the plant’s central nervous system. It connects the machines that automate the various production tasks, such as assembly, packaging, painting, welding, and filling. It is the mechanism that defines how these machines operate and how everything is controlled. It is also all the data, heuristics, and efficiency information that is collected and brought up to a central location so manufacturing operators can see exactly what is going on through spreadsheets or analytics and use that data to get every ounce of efficiency out of their system.”
In manufacturing, automation tasks are handled by control systems called programmable logic controllers, or PLCs. “A plant has many PLCs, each programmed to do a specific task. The control system uses a combination of sensors and actuators to operate the machines that perform the incremental steps to build a product,” said Crawford. “The sensors basically tell the PLC what part of the process that product is in or what’s being done with it. They track things like water temperature in a brew process, product weight, color, or pH measurement. Actuators enable the PLC to take action as programmed by the SCADA system, such as drive a conveyor belt, apply a label, scan a bottle for cracks, actuate a relay solenoid, or open a gate to steer a product to the next station where another PLC takes over. All those connections — one PLC communicating to the next, ‘I’m finished with my part, now I’m going to hand it off to you’ — are programmed.”
The PLC is the programmable brain of the machine, and the HMI (human-machine interface) is the device that provides a visual indication of the process and a way for an operator to control actions such as the STOP/START of a machine. SCADA software can be as simple as an application that programs the PLC to perform its functions through input signals and sensors, and outputs like motor speed and pump on/off commands. More complex SCADA examples scale and expand on the PLC program by adding visual platform representation, interaction with systems for advanced ordering, and scheduling and planning all plant operations.
The SCADA system is what programs the controllers of each machine to perform its product-building function. This network interconnection ensures cooperation and synchronization. As a part moves through this automated process, every step is monitored, measured, and validated before moving on to ensure those incremental steps and transfers happen correctly. Because it accounts for all materials used in the process, it can estimate and provide inventory values, calculate actual cost of goods sold, and even negotiate in real time with vendors for the best delivery terms.
More advanced SCADA systems may have all the information represented on a touch panel screen. The highest levels of SCADA tie into the enterprise level of the company to purchase new raw materials, for example. “You might have built 10,000 widgets that day and through the process your machines have consumed 100,000 different parts. The SCADA system is connected to a business-to-business portal that enables it to order what is needed automatically,” said Crawford. “In addition, all that information is updated in what is called a historian or a database. So not only is it ordering the parts, it is also providing data on how optimized your process is.”
The information collected helps plant managers make decisions based on factors such as energy use, how much time it takes to make the widgets needed to fulfill the purchase order, how many shifts are needed, and whether the workers on each shift are getting straight time or time and a half. By considering all these variables, a decision might be made to intentionally operate at 80% capacity because the cost-benefit analysis shows it is more efficient to limit energy use on high-temperature days.
“All this equates to an efficiency number that helps the people in finance determine if they are losing money by running for three hours longer. All those manufacturing metrics percolate up to a single place where multiple computer programs and applications like SAP, CRM (customer relationship management), ERP (enterprise resource planning), and MRP (materials requirements planning) can access all the information in real time about the manufacturing plant. This is where the top echelon of SCADA applications, people, programs, and companies live,” Crawford explained.
Interconnects in SCADA
Imagine a manufacturing plant that produces canned vegetables. The manufacturing line has machines with big motors that pull in sheet metal, which is then cut and stamped into squares. Rollers form the squares into cylinders, seam sealers weld the seams shut, and a press puts the bottoms onto the cans. A spray nozzle coats the cans with an anti-rust agent. Interconnects enable the functionality of motors, stampers, sensors, electric eyes, and robotic equipment in a way that allows them to be easily serviced and maintained. “Everything is modular and tied into the SCADA system,” said Crawford. Because there is so much data and power flowing, so many analytic parts and pieces, and so many interlocks and safety contacts, a seam welder might have 800 electrical connections. The connectors used in these systems are specifically made to address each unique kind of connection. Some carry data, some carry power, and some carry relay signals. There are also many kinds of power with hundreds of different requirements for current and data.”
This wide variety of machines that have many different functions are interconnected within the SCADA system, but the way they physically connect to the world of work — the motor that turns on and off or the sensor that detects that the package is right in front of it — requires connectors as well. Sensors and actuators are generally installed with connectors to facilitate removal and replacement for cleaning and maintenance, or for when they fail.
Benefits of SCADA
At its most basic, SCADA provides an automation application that is easy to program and deploy. For large manufacturing plants, SCADA provides access to and integration of the key performance indicators and metrics needed to understand how well the operational aspects of the entire plant are running. This data is essential for optimizing resources, maximizing efficiency, and archiving critical parameters so operators can pinpoint when and where processes are having problems. Deeper penetration into the data from the cloud to the drill press has always been hard for SCADA companies to achieve but more and more automation platforms are becoming available that make every piece of data available with flat data models and protocols, including variable data as well as quality of service, runtime hours, number of resets, firmware revisions, and CPU loads, Crawford said. “This is all important information that wasn’t considered meaningful, nor was it available, to operations from the 1980s throughout the 2010s.”
Changes are ahead
“The workforce is changing. Entrants into our field have different expectations for how they access platforms, how they code, the immediacy of information, and what they can do with it,” said Crawford. “In the last 10 years the cloud has provided some disruption. Some more traditional on-premises historians and SCADA companies have given way to multi-tenanted enterprise-level software that makes things available to all. AI will undoubtedly impact the space with technology like sketch to code and sketch to SCADA.”
The biggest area of concern and opportunity for change is simplification, he added. “Software programs like SAP and CRM systems are complicated and expensive to operate and adapt. Intuitive, easy-to-navigate user interfaces will be more commonplace. Devices, services, and platforms will connect easily both within a business and to externals, like customers and vendors.”
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