Process Automation in the IoT Era
This article appeared in IMS AWWA- The FLOW magazine
The global Internet of Things (IoT) market is currently worth $151B and projected to be worth more than $1,567B by 2025. It is estimated that there are over 7B IoT connected sensor concentrators and devices that will grow to 21.5B by 2025 (Lueth, 2018). How will IoT affect the water industry? What elements will provide value to end users? How does the integration of these elements change how equipment is built, automated, controlled, and supported? These are the questions and market forces that the executive team of Intuitech faced in 2017.
For the last twenty years Intuitech, a Salt Lake City based equipment manufacturing company, has been designing and fabricating skid-based equipment tailored to piloting in the water and waste water industry. Intuitech holds a unique vantage point for water treatment automation. In many ways, Intuitech has been heavily influenced by the equipment and practices used in the construction, automation, and programming of full-scale facilities. Intuitech is also influenced by the machine building industry. From the standpoint of a machine builder, size, cost control, and speed of fabrication are driving factors and standardization is desired.
Beginning in 1999, Intuitech began using the Schneider Electric Modicon Momentum Programmable Logic Controller (PLC) for machine automation. This PLC was commonly used in full-scale facilities and presented a unique physical architecture that eliminated the need for interfacing terminals, provided terminals for power distribution to field instruments, and decreased fabrication time. In 2017, the Momentum PLC was considered a mature product. A firm obsolescence date had not been published, but manufacturer had ceased development of new features for the device. Over this time period, Intuitech also witnessed significant changes in the industry, especially in terms of instrumentation and device connectivity options.
Most PLC platforms are based on four types of hard-wired inputs and outputs (I/O). I/O is regularly presented as Analog Inputs (AI), Analog Outputs (AO), Discrete Inputs (DI), and Discrete Outputs (DO). Analog instruments are used when a range is needed. For example, many flow instruments are considered AI devices and translate their measured value to an electrical current between 4mA and 20mA. The PLC translates this electrical signal and returns the flow value the instrument is measuring. Common analog output devices are pump controllers or modulated valves where there is a desired range of operation. Discrete control is similar but instead of operating in a continuous range, signals are either on or off as with a switch or a relay.
Over the last decade, Intuitech has witnessed more instruments and devices being controlled over protocol based communications. Protocols define the way electronic devices communicate with each other. They are analogous to languages. If two people speak French, they can share a lot of information with each other. If a PLC and a device such as a pump’s variable speed drive or an instrument, speak the same language then a lot of information can be passed between them.
Early serial protocols, such as RS-232 and RS-485, were slow, subject to signal interference, and required cumbersome configuration and troubleshooting. These protocols provided more information than analog or discrete signals, but their limited speed and bandwidth made them impractical in the IoT era. With an ethernet connected instrument or device, that utilizes protocols such as Modbus TCP/IP, Ethernet/IP, and Profinet, Intuitech took their first step towards an IoT compatible solution.
Two examples that illustrate the power of ethernet connected devices are Variable Frequency Drives (VFD’s) and pilot valve manifolds. Intuitech utilizes VFD’s to control the speed at which a pump operates which can then increase or decrease the amount of fluid being moved by the pump. Controlling a VFD with traditional AI/AO/DI/DO control would include a run/stop command (DO), run status feedback (DI), drive speed output (AO), drive speed feedback (AI) and fault signal (DI). Each of these signals is wired with an individual electrical connection. An ethernet connected VFD enables numerous data points that are passed at high speed between the PLC and VFD. This allows Intuitech to not only control the VFD but also gather additional diagnostic data about the drive and its operation all over one push-and-click connection. Intuitech also saw the value of ethernet connected devices with valve manifolds. On some of Intuitech’s water treatment skids, there are as much as fifty discrete valves. Under a traditional I/O system, this would require several high density DO cards and the termination of fifty pairs of wires. With an ethernet based solution, a single ethernet connection can be made to maintain the same level of control.
The downside of ethernet connected instruments and devices is the added cost and programming complexity. Field devices now need to be equipped with control boards that speak the same protocol as the PLC. In some cases, purchasing an ethernet enabled device can increase the price of the device 25%-50% over an AI/AO/DI/DO device. Additionally, each device is unique in what information is provided over ethernet and how the information is organized. Regardless of these downsides and because of the simplicity of wiring and the increased diagnostic benefits, Intuitech has moved many field instruments and devices to ethernet based communications.
The planned obsolesce of the Momentum PLC and the desire to build upon the capabilities of IoT connected instruments and devices caused Intuitech to step back and evaluate other process automation system options. The final element that propelled them to undertake and upgrade their system to a fully integrated IoT enabled system, was the increased prevalence of a relatively new protocol called IO-Link.
IO-Link is a standardized IEC 61131-9 I/O technology for communication with sensors, devices, and actuators. It is a powerful point-to-point communication protocol with similar benefits of ethernet based protocols. IO-Link technology is based on the well-established 3-wire sensor and actuator connection. IO-Link has added the functionality of an ethernet based system and is wired using simple premanufactured cable sets.
With the additional market availability of IO-Link devices, Intuitech is able to have every field device on a skid become an intelligent IoT compatible instrument. With IO-Link, every pressure, level, and flow transmitter can provide much more than just the process value. For example, an IO-Link enabled sensor can provide historical maximum and minimum values, instrument health, and other diagnostic data. Additionally, whereas AI devices needed to be scaled in the PLC, IO-Link provides the actual process value, which eliminates the possibility of conversion errors in the PLC.
As with any new technology, new approaches are required to leverage features enabled by IO-Link devices. Applying these devices to the fabrication of water treatment equipment results in smarter equipment but Intuitech knew that the additional IO-Link data needed to be carefully curated so as to provide meaningful information to the end user to improve the piloting experience.
Additionally, IO-Link provides the ability for sensor configuration to be automatically sent to the device’s memory, allowing for plug-and-play replacement of configured instruments. For Intuitech, this was an important feature, since it allows tool-less replacement of an instrument in the field by untrained personnel. Previously, when an instrument would need to be replaced, that instrument would be shipped to Intuitech for configuration. With IO-Link, the end user can plug in a replacement instrument and the device will auto-configure. This feature of IO-Link devices adds a significant benefit to small and rural utilities who do not have the manpower for a full-time controls staff. End users can also move from a reactive state to a proactive state for maintenance, where sensors can provide insight into their health prior to a failure.
Knowing they wanted to leverage IO-Link and ethernet connected devices, Intuitech’s last major decision was to select a PLC to replace the Momentum. After comparative analysis of plant system and machine build PLCs, they selected an alternative Schneider Electric PLC. The new PLC is designed as a high-performance solution for modular machines and distributed architectures. The multi-protocol PLC has no requirement for on-board I/O, in fact traditionally wired I/O is all but non-existent under this new architecture, which greatly lowers the unit cost compared to plant system PLCs. It is built around connecting field instruments and devices over ethernet and contains two embedded networks for separation of client and machine networks for added security. It offers a built-in web server, file transfer, and SQL services, which facilitate easy integration into control system architectures for remote machine monitoring and maintenance via apps for smartphones, tablets, and PCs.
With the introduction of a new PLC platform that supports the open source PLC language Codesys, Intuitech took the opportunity to review their programming practices and concluded to migrate much of their traditional ladder-logic code to structured text. The structured text scripting language permits more complicated coding required for supporting ethernet and IO-link connected devices and can take advantage of data structures, arrays, for-while loops, and other more powerful programming tools that can be supported by a much larger pool of programmers.
In conclusion, many factors aligned to help move Intuitech towards a new IoT enabled platform. With a plan in place, the team set standards, produced engineered drawing sets, converted existing code libraries and core application code, and conducted extensive testing of various hardware and software solutions. In all, the process took about 12-15 months to complete. Key elements of success were having a clear direction from the executive team with the allocation of resources to complete the migration in a reasonable time frame. Additionally, Intuitech talked with their existing clients about features they would like to see and incorporated these recommendations. Lastly, Intuitech progressively selected a process automation architecture with the flexibility to meet the demands of the new IoT era.
Lueth, K. L. (2018). State of the IoT 2018. Retrieved from https://iot-analytics.com/state-of-the-iot-update-q1-q2-2018-number-of-iot-devices-now-7b/