Process analytical technology (PAT) is costly to maintain. It involves regular inspections that must be performed on site by a PAT expert at fixed time intervals. However, through remote access based on the NOA (NAMUR Open Architecture) principle, the status of the measuring device can be checked online and in real time using the vitality data. The costs associated with on-site inspection are eliminated and lengthy troubleshooting is no longer required.
INVITE GmbH is a private-public partnership between Bayer, TU Dortmund University and Heinrich-Heine University Düsseldorf. As a link between the life sciences industry and research, INVITE provides a platform for innovative projects in the field of digital process and laboratory automation as well as formulation development.
As part of INVITE, the Digital Showcase Center also demonstrates new technological approaches. Among other things, it features demonstration systems for the NAMUR topics of MTP (Modular Type Package) and NOA (NAMUR Open Architecture). The demonstrator that was built to test the NAMUR Open Architecture can be used to simulate the various applications and environments of NOA. Together with Bayer and Lanxess, the partnership has identified online condition monitoring, for PAT measuring devices in particular, as an application that can benefit hugely from the NOA concept.
Reliable extraction of system data
The core purpose of NAMUR Open Architecture is to generate greater benefits from existing system data. Unfortunately, the situation with older existing systems is often such that the relevant data is difficult to access. A reliable interface for making the data useable does not exist in the system. The NOA concept now allows the standardised and secure export of this data from the existing system, which usually does not have state-of-the-art interfaces. To achieve this, the classic automation pyramid is extended to include a side channel through which access-secure communication takes place.
In this context, the term ‘data diode’ has been coined. It is intended to make it clear that information can be extracted without anyone being able to penetrate the system. All details on the NAMUR Open Architecture are listed in NAMUR Recommendation (NE) 175.
Improved orientation with an information model
A flexible and secure data interface has proven to be an important building block for realising the NOA concept. The OPC UA data exchange standard covers all the characteristics that are necessary for this. OPC UA is an abbreviation of Open Platform Communications Unified Architecture, and its name is a huge clue as to the reason behind the standard being created: to connect platforms via a unified architecture.
This type of connection is also often known as IT/OT integration. This refers to the field level (operational technology, OT) and the office area (information technology, IT) being coupled together. The OPC UA interface can be integrated just as well into a small field controller as it can into a complex enterprise tool. Because OPC UA can also incorporate numerous state-of-the-art security features, the standard is particularly suitable for the NOA concept.
A further OPC UA property, known as the information model, is also ideal for the application. With such a model, the interface can be adapted in terms of the structure and the namespace of the data. This benefits the user; in the case of the abovementioned demonstrator, this is the person who wants to analyse the system data to optimise the application or to carry out targeted maintenance. The information model allows this person to better familiarise themself with the data because the data structure and names are standardised. This is a significant improvement, since the names of the pieces of information were not consistent before, as they were assigned individually by the sensor manufacturer (for example).
The information model for NOA is abbreviated to NOA IM and is an evolution of its predecessor, the PA DIM (Process Automation Device Information Model), published by the OPC Foundation in cooperation with the FieldComm Group. In the PA DIM, the basic information for each standard process sensor – such as temperature, pressure and flow sensors – is defined in the form of a name and structure. NAMUR now adds additional information, thus extending the model to become the NOA IM.
Intelligent software for data collection
The NAMUR Open Architecture includes the NOA IIoT server as an additional block. This server collects the information from the HART sensors installed in the field, most of which contain a variety of informative, but as-yet unutilised data. This is managed by intelligent software for the compact PLCnext Control field controllers from Phoenix Contact.
The NOA IIoT server connects to HART-compatible sensors over a HART gateway via a branch line, identifies the individual devices, and uses the specific description file that is held available in a large pool. This allows all of the information to be retrieved from the respective sensor and made available on the OPC UA server in a uniform format. A remote I/O station from the Axioline P product family for process engineering systems will soon be integrated into the solution, so that the NOA IIoT server can communicate directly via the bus coupler.
Extended definition of the vitality data
The data described in the NOA IM depends significantly on the specific application. The primary purpose of the PA DIM information model is to identify the measuring devices. It includes information such as the model designation, serial number and software revision. These values do not play a role in the measuring task.
For the online condition monitoring application, however, specific values are required that are based on the respective measuring task. For this reason, the NAMUR Process Analysis Technology Working Group has defined what is known as vitality data for various PAT measurement tasks. This vitality data is an extension to the PA DIM and enables the user to carry out an inspection of process analysis devices via remote access based on the information transmitted. For example, the glass impedance, the impedance of the reference electrode and the date of the last calibration are required for a pH measurement.
A demonstrator was set up in the INVITE technology centre to test the technical realisation of the online condition monitoring application with NAMUR Open Architecture. This maps several pH measurements taken by devices from different manufacturers. In addition, the demonstrator was also equipped with the NOA IIoT server from Phoenix Contact.
Timely availability of a device-specific description file
Realising online condition monitoring on the demonstrator revealed two challenges. The first involved branching the HART signal off to the NOA IIoT server. The solution to this depends heavily on the respective situation in the brownfield. For many applications, however, using HART-transparent separators, which pass the HART input signal transparently on to two output signals, is sufficient.
The second challenge arose from the device-specific description file. In-depth knowledge of the HART communication of the respective device is required to create the description file. For this purpose, the manufacturer of the measuring device must provide support. It is therefore important for the user of the NOA IIoT server that the description file of the installed device already exists or is created beforehand.
Automated data structure export
Upon installing the NOA IIoT server and generating the description files for the INVITE demonstrator, the key advantage of a uniform information model was clearly evident. Despite using devices made by different device manufacturers, the data structure on the OPC UA interface of the NOA IIoT server is identical for all devices. This structure can then be exported automatically to data histories or cloud applications.
The PAT expert is now able to call up all vitality data from the measuring devices via remote access. The values are sorted and prioritised in accordance with the NAMUR Process Analysis Technology Working Group, and are available with uniform syntax and semantics for all devices. They can then be used in trend analysis systems or other maintenance software systems. In addition, maintenance costs are reduced because inspections can be performed via remote access rather than locally, and the maintenance schedules can be event-based rather than time-based.
“The next step is to collect vitality data in the production facility. This pilot project will thus be used to check whether the selected vitality data proves itself in day-to-day operations. The aim is to adapt the NOA information model precisely to the respective application,” concludes automation engineer, Alexander Wittenbrink.
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