Field devices with self-monitoring capabilities aren’t new. Indeed, the User Association of Automation Technology in Process Industries (NAMUR), Leverkusen, Germany, issued its NE-107 standard on self-monitoring and diagnostics of field devices in 2006. However, significant developments are occurring and vendors are enhancing capabilities in a variety of ways.
For instance, Dietmar Haag, product manager for level management, Endress+Hauser, Maulburg, Germany, notes: “In addition [to meeting the NE-107 standard], we offer plenty of advanced diagnostics to ensure signal quality, measuring performance, and to detect foaming or build-up for better predictive maintenance and process optimization.”
Such capabilities enable effective level measurement despite the tough challenges posed by some applications today. He cites a recent project for a petrochemical customer in the Middle East as typifying these challenges. The company wanted to upgrade its existing automated tank gauging (ATG) system to comply with the latest recommendations of the American Petroleum Institute. This required an independent high-level alarm system to prevent overfilling. However, the system also had to be independent from any device and method used for ATG. The specification required TUV-certified high safety integrity level (SIL-3) level switches based on the vibrating fork principal — together with continuous self-monitoring and diagnosis (Figure 1).
Endress+Hauser’s answer included its failsafe Liquiphant S level switches, and a control cabinet equipped with SIL-3-rated programmable logic controller and inputs/outputs (I/O) as well as graphic and text displays, SIL sounders and beacon lights. A fully-automated proof-testing procedure and maintenance-free instruments contribute to a lower cost of maintenance, too.
Endress+Hauser’s latest innovation is what they call Heartbeat Technology for reliable and flexible proof testing. The hardware and software (details about both remain guarded) are designed to reduce or even eliminate the plant downtime often needed for field-device maintenance and recalibration.
Heartbeat Technology initially is appearing in the company’s new Proline flowmeter platform with the aim of significantly lowering the rates of dangerous undetected failures in accordance with IEC 61508, the functional safety standards of the International Electrotechnical Commission, Geneva, Switzerland. Time-of-flight level instruments will get the technology later this year; it eventually will become a component of all the company’s level-sensing devices.
With the technology, users can initiate reliable, automated test programs without impacting the running process. The in-situ device verification can be activated with the push of a button or click of a mouse from the field network or via secure internet connection if a web server has been integrated. Following activation, the device then performs a self-test that covers all functional areas.
For measurement devices used in SIL-rated systems, Heartbeat Technology also can afford greater flexibility in planning and minimize downtime in proof testing, e.g., letting staff perform more-complex procedures such as instrument calibration only when needed.
The technology also expands diagnosis and monitoring functions such as process and instrument diagnosis in accordance with NE-107 recommendations. These include the generation of clear instructions, plus trend analyses that detect systematic errors and process influences —leading to early identification of changes in device function or the process itself, enabling proactive maintenance.
“The technology offers a device check — a verification — without process interruption and also additional data monitoring which can be used either to optimize the process or for predictive maintenance for the device itself. For customers, it means improved availability and safety, plus access to additional sensor and process information,” explains Haag.
Access Via App
Improved diagnostics also is a key feature of the Vegapuls 64 radar level sensor for liquids. Launched in May by Vega Grieshaber, Schiltach, Germany, the device allows users to access its diagnostics, as well as operational data including measured value, event memory and sensor status display, echo curve and Bluetooth range information with a smartphone or tablet via an app.