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MAR-APR 2019

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INTECH MARCH/APRIL 2019 27 SYSTEM INTEGRATION A primary reason for moving to wireless sensors is to minimize installation cost, because home-run conduit and wire are removed from the equation. But even among wireless options, there are sustain- ing cost considerations, such as how often batteries need to be replaced. Some industrial wireless standards, such as ISA100 Wireless, are already established wireless lo cal area networks in many process plants for critical operations like monitoring and control of equipment, or even safety-related automation. This type of industrial wireless must have extreme ly high reliability and operate in a close to real-time manner for process control and safety applications. By comparison, the use of Internet of Things (IoT) and Industrial IoT (IIoT) devices throughout facilities is quickly expanding for monitoring and even controlling noncritical infrastructure relating to maintenance and environmental management. For these types of applications, there are many rea- sons to select a protocol within a networking class known as low-power, wide-area (LPWA) network- ing. A prominent protocol in this area is LoRaWAN. Implementing LPWA for IIoT devices in con- junction with a protocol like ISA100 Wireless for process devices lets end users strike an optimal bal - ance between price and performance to achieve advanced, efficient, and safe plant operations. This article examines why LPWA is a compelling choice within a sitewide wireless network architecture for implementing IIoT devices. Operations and infrastructure overlaps and gaps When designing or expanding sitewide wireless network architectures, users must categorize the desired service for various field devices. Typical plant or factory wireless needs can be roughly divided into one of four types: safety, operation, maintenance, and environment (figure 1). The first two are considered operational, while the last two are infrastructure related. Safety is usually considered the most criti - cal application, followed closely by operation. Maintenance and environmental monitoring are most likely somewhat less critical, but im- portant, nonetheless. With this in mind, wire- less networking technologies should be selected based on these roles. To do this, it is helpful to review some specific requirements for operational networks in compari- son with infrastructure networks. Weighing these requirements drives the network technology selec- tion, since sometimes the choices are gray rather than black or white. For instance, some charac- teristics such as "reliability" are always desirable. However, high reliability may be crucial in some applications, while lesser reliability may be acceptable in others. Operational net- works, such as ISA100 Wireless, must directly operate process devic- es and safety systems. Therefore, these net- works are expected to deliver: l real-time monitor- ing and command with less than 1-second response l high reliability of communication infrastructure l high integrity of data transmission l excellent security l medium-range communication l flexible topologies (redundancy, backbone, mesh, star) l coexistence with wired systems l robustness within typical industrial environments Infrastructure LPWA networks, on the other hand, typically monitor equipment and the environment. Therefore, these networks are expected to have: l wide-area coverage, kilometers or tens of kilo- meters l ultra-multipoint connections, up to 1,000 or even 10,000 points l variable communication cycles ranging from 60 seconds to 60 minutes to three days l easy physical installation to minimize field costs l a possibility for data sharing by multiple top- level systems l a focus on long-term data as opposed to instan- taneous values l suitability for use in multiple operating conditions l relatively low cost per point Based on the listed criteria, almost any conceiv- able field device can be logically categorized. Set- ting aside cost and technical details, a significant deciding issue is the poll time required for a signal. FAST FORWARD l ISA100 Wireless is already established for critical process automation operations. l IIoT sensors are often numerous and widely distributed but have low required polling rates and are typically used for noncritical maintenance and environmental sensing. l LPWA, specifically the LoRaWAN protocol, is a low-cost wireless technology suited for connecting to many IIoT devices over a wide area, powered only by long-life batteries. Operation Maintenance Safety Environment Plant ISA100 Wireless LPWA Figure 1. Typical plant wireless categories: Process plants usually have safety, operational, maintenance, and environmental net- working needs. The first two are best served by an operational network like ISA100 Wireless, while the last two find a better fit with LPWA networking.

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