The remote terminal unit (RTU) has been a workhorse of the petroleum industry for more than 20 years — a thoroughly domesticated animal often seen as just one more element, more or less, of the post-industrial landscape. The last several years, however, while hardly acting as a disruptive technology, RTUs have evolved to become a base node for the intelligent oil and gas field. An RTU is a microprocessor-controlled device installed at a remote location, such as well sites, that collects data from sensing, metering, or other instruments; codes it; and transmits it back to a central station, typically a supervisory control system (SCADA) or distributed control system (DCS). The RTU may also receive data from the central station for process execution. Today’s RTUs go a step further in that they combine advanced capabilities for automation, monitoring, and telemetry. RTU evolution has to be seen as part of SCADA market development, says Russ Novak, a senior analyst with ARC Advisory Group. “SCADA was seen primarily as a technology for the midstream. But when oil prices rose, value was seen in automating older fields. SCADA was the platform to hand for doing that. As the digital oil field concept has taken hold, SCADA has become one of the means for getting real-time information to centrally located operations centers.” As for RTUs themselves, Novak classifies them as either “dumb, smart, PLCs, flow controllers, and other.” Besides general-purpose RTUs, oil industry service companies manufacture or market dedicated hardware devices for things like control at the wellhead. And a whole new class of suppliers is emerging for subsea applications. “When RTUs are replaced,” says Novak, “it’s not because they wear out. Rather it’s because the intelligence capabilities of information technology and software are needed. For the same reason, IT departments are increasingly involved in their specification.” Semaphore is an Australian-based developer of SCADA, RTU systems, and telemetry solutions. In a recent white paper, “Infrastructure Management and Mobile Asset Management,” the company outlined its take on why RTUs remain a relevant technology. At issue is the need to balance priorities that include remote site automation, monitoring, and telemetry, such as might be needed in oil or gas fields. Data communication equipment (DCE) such as a cellular modem for telemetry, a data logger for monitoring, or a PLC for automation each accomplish their assigned task well, but • DCEs provide telemetry, but only limited data logging capability • A data logger doesn’t provide automation capability • PLCs today do integrate with DCEs, but pain comes from having to integrate multiple DCEs Thus, an automation team might find itself having to install all three pieces from different vendors. In contrast, says Semaphore, the latest RTUs combine PLC automation, data logging monitoring, and multiple DCE telemetry capabilities. A further innovation is that RTUs today are often equipped with IP/Web capabilities. Semaphore says its RTUs include an “integral web server, IP communications, and “push” messaging via e-mail, FTP, and SMS text.” The gist is that users can access site information by cellular phone, PDA, or laptop, i.e., web pages served via the internet or intranet, email messaging, and SMS text messaging.
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