Under the brim of his hardhat, Dana, the instrument tech, had scrawled the network ID and join key for the two WirelessHART networks in his section. This was essential to adding and/or replacing digitally integrated wireless transmitters, and the potentially lengthy network ID (up to six digits) and join key (up to four integers of eight digits each) was both something to be known and something to be guarded. Dana had become proficient at configuring the wireless instruments using his new Trex communicator; he was also familiar with the browser-based management tool for the plant's growing wireless sensor network.
In today’s world, a large proportion of measurements from wireless instrumentation is brought into legacy systems, even more into modern ones, using Modbus. As such, each variable of interest is mapped to a Modbus register, and the corresponding register is read and associated with its tag in the DCS or PLC. Once done, this configuration is stable and reliable. But how easy is device replacement? As any infrastructure ages and applications are added or modified, the individuals who understand how it all fits together may not be readily available. What if a device needs replacement while Dana is on vacation, and his hardhat is in his locker?
Whither change management?
In the WirelessHART deployment, a new device out-of-the-box requires a few more settings to replace an existing one. These are all things that can be set with a properly equipped and connected handheld device or a laptop with a HART modem and appropriate software. A procedure detailing variables like Network ID or Join Keys should not be hard to develop, and helpful wizards aboard a handheld configurator can get one through most of the critical settings. If you’re replacing a flow transmitter that requires a square-root linearization and meter factor, all those settings need to align as well. A handheld or laptop might be capable of uploading an old device’s configuration, but that process can be tough to capture in a standardized procedure.
Having deployed a wireless infrastructure for battery-powered wireless field devices, the applications in Dana’s plant proliferated, in several cases owing to the imaginative thinking of Dana and operations specialists. Wireless pressure gauges in analyzer sample systems forewarned of plugging. Acoustic sensors on pneumatic solids conveying lines assured they were moving material. Could acoustic sensors with integral temperature sensors offer a clue about whether a pump kickback line was flowing freely or plugged with polymer or catalyst solids? Seems like they did, and within a year or two the improvised application was cited in a HAZOP as a safeguard. Digital transformation and new applications based on proliferating sensors—the previously unmeasured, locally monitored or simply inferred—are becoming common. Even the most fractious cultures might welcome instrumentation that assists either management or front-line operators to support or defend their priorities and choices, but their configuration and maintenance can't be left to chance.
In modern plants, instruments that participate in some way to provide a safeguard, or are essential to achieving the necessary layer of protection analysis (LOPA) risk reduction, need to be validated. These aren't safety interlocks per se, but any measurement that alerts users to take action to avert an undesirable consequence. For these, "run to failure" isn't an option. Once we rely on the new infrastructure for even economic risk avoidance, the care and feeding of the system can't be ad hoc.
Today’s world supports the easy deployment of wireless devices that require little added infrastructure or even strict management of change. If you’re fortunate enough to have a competent and enthusiastic champion like Dana, capture his or her doings in standardized procedures. And ensure that you’re grooming backups/successors, who can sustain the digital transformation after they move on. Doing so will require privileges and access to both digital field devices and networks, as well as the SCADA, PLC or DCS to which the new information is being transmitted.
