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Helga Linnartz, Business Development Flow Manager, Endress+Hauser Netherlands gives an introduction into the advantages and possibilities of advanced
One of the crucial parameters in a production plant is theavailability of production assets. When they are not available, thereis no production, which results in expenses through production loss.In order to keep the production downtimes as short as possible, maintenance of plant assets such as instruments, valves, etc. is required. There are different concepts for the maintenance of field devices, distinguishing between corrective maintenance (measures in case of malfunction) and preventive maintenance (measures to prevent malfunctions).
Fig. 1: The right amount of preventive maintenance is importantin order to keep total cost at a minimum.
Device condition
There are two different ways of planning preventive maintenance. One possibility is a time-based approach, i. e. maintenance at regular timeintervals. This has the advantage that the work involved is known beforehand and can be scheduled, in terms of costs and time. The drawbackis that this method does not take the actual device status into account. With the second option, condition-based or predictive maintenance,the condition of the device actually forms the basis for the maintenance schedule. Using this approach, the information that is read from the field device during production is analyzed for possible trends. Based on these trends, the maintenance team will then determine the optimal maintenance cycles.
Fig. 2: Overview of maintenance strategies. Preventive maintenance may be planned in two different ways; each has its own advantages.
Fingerprint
Information from field devices can be a valuable data source for condition-based maintenance. Thisis of particular importance for devices where periodic maintenance isusually not required. A case in point is the Endress+Hauser Coriolis mass meter Promass 83 with advanced diagnostics functionality. The advanced diagnostics functionality makes it possible to determine a so-called “fingerprint” of the device at regular intervals. The user is given the option of defining a reference condition. For this, various parameters are measured, forming the fingerprint of the Promass. These parameters include measured process parameters, such as mass flow, density and temperature, as well as meter variables, such as sensor symmetryand damping. This forms a picture of the meter’s behavior under knownconditions.
Application-specific
What makes the advanced diagnostics concept so interesting is the fact that the information obtained may provide an insight about application-specific errors: repeated registering of a fingerprint makes the influence of the process andthe process fluid on the Coriolis meter visible over time.
The real power of advanced diagnostics, however, lies in the combination ofthe different measured values. Through periodic control of the densityalone, temperature fluctuations cannot be ruled out, which would alsochange the density. If, however, the combined periodic check of density, temperature, reference density and sensor damping in a fingerprintshows a trend, this may be a sign of corrosion or product build-up.
Fig. 3: In the FieldTool® configuration tool, the fingerprint history is clearly shown, and trend analyses are possible.
Process knowledge
“Advanced diagnostics” allows the user to monitor thedevice condition, thus creating a prerequisite for the use of predictive maintenance. Furthermore, this functionality can provide a valuablecontribution for process monitoring. Through periodic device fingerprints and the processing of these data in trend analyses, more information is provided from the device, without affecting the primary function – supplying measured process values. In order to benefit from this added value, it is essential that knowledge of the device and thoroughfamiliarity with the process go hand in hand.
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