One of the most efficient ways to implement wireless in process applications is using a protocol that’s designed for them and has already been available for years—WirelessHART.
“Other wireless protocols are making ingresses, but many users are realizing how well-designed WirelessHART is for the process industries. Its data model and wireless physical layer covers their process applications quite well, and it’s made them easier to operate for 15 years,” says Shane Hale, global business development director for Emerson’s Pervasive Sensing and Connectivity division. “As wireless protocols from other industries come in, they don’t have WirelessHART’s data model, so each vendor uses proprietary data models and requires their own decoder files to make data available to host systems—and it’s up to the users to implement them. This can add complexity and cybersecurity risks to their deployment when they trying to mix in devices from several suppliers.”
Hale reports that WirelessHART is better at delivering process variables and diagnostics without requiring users to complete detailed integration tasks. It’s best-suited to applications with 1-8-seconds or longer update rates at up to 200 meters with line-of-sight, but because of the self-organizing mesh network, devices can ‘hop’ through other devices to the gateway to dramatically increase distances covered. Depending on update rates, WirelessHART can also employ five-to-10-year batteries. Similarly, lower-power LoRaWAN may run over longer distances, but it’s limited to 60-second or longer update rates, so its preferable for applications that only need to deliver their data a few times per day.
Meanwhile, Hale adds that larger-bandwidth Wi-Fi must have onsite power to handle the stronger radio power required. Likewise, its added capacity usually makes Wi-Fi more costly than LoRaWAN and Wireless HART, even though it’s a public protocol. Even so, Wi-Fi is less expensive than 4G LTE and 5G cellular’s bought-and-paid-for spectrum over the long term as the radio spectrum is a recurring cost and may come with data rates, too. However, some of these traditional costs may ease as European and North American regulators free up some less-used 900 MHz spectrum and sell it at low prices, which should give users some savings on bandwidth.
“Onsite assessments may not be needed as much as they were in the past, but users must still focus on what problem they want wireless to solve,” adds Hale. “In general, operators who need operator-displays in the field should use Wi-Fi, while WirelessHART and its long battery life are best for monitoring pumps, valves, and other process and reliability measurement updates.”
