One of the frustrations of dealing with a sick infant or pet is that they can’t tell you what’s wrong. Diagnosing the situation is difficult because you can only infer the cause from their behavior or perform diagnostic tests. For a long time, that was also the problem with field instrumentation. An instrument tech would have to look for signs of malfunction, and hopefully identify the problem by trying different possibilities. Unfortunately, this could be time-consuming and might not reveal the actual cause. Such is no longer the case, or at least it doesn’t have to be.
Modern field instruments can tell you exactly what’s wrong through their device diagnostic capabilities, if you’re willing to listen. I explain how this works in the second article in a series about the larger picture of automation diagnostics published in Process Instrumentation, Device Diagnostics Ensure Instrument Health. (The first article is an introduction to the topic and well worth a read.) The series will cover four ways these capabilities can be used in process manufacturing environments. This article looks at what the instrument can tell us about itself.
Instrument diagnostics grew out of the development of transmitter electronics necessary to linearize, range and convert raw analog data into engineering units, and to standardized data transmission formats (e.g., 4-20 mA current loops). As the data analytics capabilities of transmitter electronics grew in sophistication, adding diagnostic capabilities was the next development step. Once communication protocols such as HART and Foundation Fieldbus became available, they provided the means for an instrument, such as a pressure transmitter, to convey new types of information in addition to the main process variable.
Some of the early diagnostics were pretty rudimentary, but many companies built their reliability programs on them because they were predictive and could warn when problems were developing. Those companies found them to be a huge advance, and they are still just as critical today as ever. But for Emerson, they were just a beginning, and their device diagnostics have become much more sophisticated, especially for flow meters. For example, Emerson’s Smart Meter Verification technology:
When Emerson completes a flowmeter installation included in this program, it undergoes a series of tests to determine its initial characteristics, or we can say, its signature that can be imprinted in the transmitter’s memory. The objective is to perform this test again, whenever desired, to verify that nothing has deviated from the original signature.
So a flow meter, such as Emerson’s Micro Motion Coriolis Mass Flow Meter, can look at its own signature and see if there is any deviation from when it was built and first put into service in the plant. The same applies to many Rosemount Magnetic Flow Meters and some Rosemount Ultrasonic Flow Meters. Operators can check at any time since the verification only takes a few seconds and is virtually continuous. This also saves a lot of labor and increases unit availability because Smart Meter Verification can extend the period between calibrations. The article goes into some eye-opening success stories showing how companies are deploying this valuable capability to improve operations. Looking ahead:
In the next three articles in the series, we will look at what instrument diagnostics can determine about a process, how they can point out installation and maintenance problems, and how to implement practical end user solutions. Instruments provide a wealth of data, and advancements continue to turn this data into actionable and useful information.
Visit the Field Device Management pages at Emerson.com. You can also connect and interact with other engineers in the Downstream Hydrocarbon and Chemical Processing Groups at the Emerson Exchange 365 community.
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