Just as you can't have too many friends, level measurement applications can't get enough ease of use, reliability and safety. Thanks to increasing process industry needs and user demand for them, these are the three unifying priorities that drove the design and development of Emerson Automation Solutions' new SIL 3-capable Rosemount 5408 Series non-contracting, radar level transmitters for continuous measurement and its world's first Rosemount 2140 vibrating-fork, liquid-level detector with wired HART for point-level measurement, as well as their dedicated Rosemount 5408:SIS and Rosemount 2140:SIS models for safety instrumented systems (SIS).
"We're making big technical leaps in both the non-contacting radar and vibrating-fork categories because level measurement must now, more than ever, reliably safeguard profitability for users. They're dealing with recent shifts in oil prices that are radically altering process market rules, chemical applications that must simultaneously supply four times as many unique mixtures, and recipe lifespans half as long as they were five or 10 years ago," says Andreas Hessel, strategic product manager, process radar level measurement, Emerson. "Ease of use is critical, not just because human errors still account for 25-40% of accidents, but also because a whole generation of experienced engineers is now retiring. One estimate projects that 30% of the current process engineering workforce will be retiring in the coming five years. Finally, process safety must be an aggressive priority because overfill prevention regulations are becoming tougher, and expected IEC 61511 compliance with SISs is spreading rapidly."
To deliver the ease of use, reliability and safety users need, Rosemount 5408 incorporated human-centered design principles, but it's also designed to simplify many operator tasks. Pictorial instructions and an intuitive software interface guide users through installation, commissioning, proof-testing, operation and maintenance. And, enhanced, on-board diagnostics support preventive maintenance and provide actionable information, streamlining troubleshooting. Rosemount 5408 can also perform proof-testing and site acceptance tests remotely.
Constant radar stream
In a departure from traditional pulsed-radar devices, Rosemount 5408 employs two-wire, 12-Vdc, loop-powered, frequency-modulated, continuous-wave (FMCW) technology, which uses a continuous echo to maximize radar signal strength and produce more robust, reliable measurements. In addition, its radar-on-chip technology replaces the typical circuit board, which removes an electromagnetic noise source that can cause signal disturbances, improving measurement accuracy and reliability. Besides having a liftoff voltage as low as 12-Vdc, Rosemount 5408 has a unique, embedded power back-up that eliminates vulnerability to intermittent power losses of up to 2 seconds. Its SIL 3 rating lets it seamlessly integrate into an SIS, while its ATEX and IEC Ex approvals allow it to be installed in hazardous locations. The transmitter has no wetted o-rings and uses only stainless-steel and PTFE plastic seals, which eliminates the need to decide which material is compatible with different process media and settings.
"Running two-wire FMCW with just normal 12-Vdc power is a big game changer because we can now do level measurements in places where they couldn't be done before, including potentially explosive environments," explains Hessel. "We built the microprocessor and other pieces for Rosemount 5408 from scratch, which really gives us 'radar-on-a-chip.' Unlike other commercial, off-the-shelf devices, our chip was designed for just this purpose and process industry conditions. This means we can do two-wire FMCW for more accurate and reliable measurements because, instead of pulsed radar, it provides a constant stream of microwaves. With some limits due to individual settings, we estimate Rosemount 5408 is 100 times more sensitive than pulsed, which means much more accurate and reliable measurements, even with interference from foams, turbulence and condensation in tanks."
To help troubleshoot sporadic behavior without constant monitoring, Rosemount 5408 also carries an embedded log of measurements, alerts and echo profiles. These make it possible to review past measurements, alerts, trends and other process behaviors for up to the past seven days. Looking forward, the transmitter has predictive diagnostics that alert operators and recommend actions. "If the transmitter's antenna is getting coated, it will notify the user to fix it before its signal gets lost," adds Hessel. "If its power drops and recovers, it will report that it had a drop but it’s OK now, and that it should be checked soon."
The transmitter's safety version, Rosemount 5408:SIS, is certified to IEC 61508 for use in a SIL 2 loop with redundant instrumentation required.
"This is the only level transmitter on the market recognizing that overfill prevention and SIS integration is more than just a certificate," explains Hessel. "For example, IEC 61511 sets requirements on the last point in time when proof testing must be performed, but users want to schedule it to occur during planned shutdowns to not interrupt a running process. As a result, using Rosemount 5408:SIS in any common-practice, SIL 2 safety loop, the proof-testing interval can easily accommodate one-, three- or even five-year turnaround times."
Hessel adds that proof-testing for Rosemount 5408:SIS can be performed remotely from a control room, and it doesn’t require interrupting the process by changing tank levels, removing the transmitter from the vessel, or any temporary or permanent transmitter setting changes.
Hessel reports Rosemount 2140 combines proven-in-use Rosemount short-fork technology and the HART functionality of the wireless Rosemount 2160 to create a new wired solution. It complements the complete 2100 portfolio, but 2140 is a completely new product specifically designed for SISs and critical control applications where HART is already used. Unlike the 2160, the 2140 includes proof testing and smart diagnostics, along with other features.
Rosemount 2140 performs in high temperatures and harsh conditions unsuitable for other level detectors, and it's easy to install and maintain because there are no moving parts. It's virtually unaffected by flow, bubbles, turbulence, foam, liquid properties and product variations. It can be used to monitor not only liquids, but also liquid-to-sand interface, which can be used to detectbuild-up of sand or sludge deposits in vessels such as separators. An optional, integral LCD display shows switch output states and diagnostics, allowing local inspection, or data can be viewed remotely in the control room from the host system such as a DCS.
Compatible with HART 5 and HART 7 hosts, Rosemount 2140 enables continuous monitoring of electronics and mechanical health with smart diagnostics. For example, the frequency-profiling function continuously monitors fork vibration, and sends a process alert if the instrument sees an unusual frequency or detects a trend change in the frequency. The power advisory function monitors voltage and current, and sends a process alert to indicate potential issues that could become problems such as corrosion.
"Rosemount 2140 is clever because it's a wired HART detector and not a simple switch, so it uses changes in frequency and vibration over time to determine if its forks are coated or corroded, and alerts operators when it needs maintenance or before," adds Hessel. "What's fun about Rosemount 2140 is it can still be used as a simple switch when needed."
For safety applications, the detector's dedicated safety version, Rosemount 2140:SIS, is certified to IEC 61508, with a 97% safe failure fraction and 96% diagnostics coverage, making it one of the safest SIL 2 devices available on the market. Rosemount 2140:SIS also has fully-integrated, remote proof-testing, which eliminates the need to access the top of a vessel to extract the detector from the process.