Open asset management with FDT: the core of a ‘smart’ process plant

Field Device Type (FDT) technology remains one of the automation industry’s best-kept secrets. In spite of this, it is rapidly gaining market acceptance by simplifying the digital communication between a plant’s field devices and its control environment. It is at the heart of a ‘smart’ plant’s IT infrastructure and can deliver major cost savings to the plant’s operations.

The FDT Group AISBL recently announced that the FDT specification unanimously passed the vote of the international standardisation community - represented by 26 national committees - to become international standard IEC 62453. The openness that is guaranteed by the new standard will encourage more plant operators to implement this technology in their facilities, and a growing number of field device manufacturers to incorporate it into their products. Wil Chin of the ARC Advisory Group commented, “The formal approval as an IEC standard, coupled with the adoption by virtually all automation suppliers, will accelerate the already robust adoption of FDT technology in the process, hybrid and discrete industries.”

To understand what the technology offers and how it can be implemented, we need to review the history of its evolution.

Over the past three decades, the evolution and industry acceptance of intelligent field devices has created exciting new opportunities for process optimisation by providing bidirectional digital information flow for an expanding range of data from industrial automation processes. Not only does this data include the measured variables (PVs) but also configuration, troubleshooting, and diagnostic and asset management information.

In the past, field device manufacturers developed proprietary protocols and hardware communication tools to extract this data. Then in the ‘90s, the HART specification, as we know it today, defined instrument configuration protocols. It standardised basic commands, common practice commands and device-specific commands to give manufacturers flexibility in device definition. The resulting device description (DD) enabled the products to function in an open environment. At about the same time, the DDL concept was extended to accommodate the requirements of open fieldbus technology, (FOUNDATION Fieldbus, Profibus, etc) and the resulting extended language set adopted the name EDDL (electronic device description language). The device descriptions that come from EDDL support are called EDDs. EDDL continues to be extended to provide more functional support; for example, graphical data, information storage and information relating to product compliance with standards such as NAMUR NE 105.

How does the FDT/DTM technology work?

FDT technology comprises three key components: the frame application, and two device type managers (DTMs) - the device DTM and the communication DTM.

Figure 1: Frame applications offer a rich user interface.

To better understand the functionality of these components, consider the analogy of the internet, where a standard web browser allows users to view countless web pages created by different content providers. The host system supplier provides the frame application, just as Microsoft supplies the Internet Explorer web browser. In the same way that a web browser opens a web page that contains content from its originator, an FDT frame opens the device DTM, which is the plug-in software from the device manufacturer.

Similar to a web browser, the frame application has menu bars, toolbars and a navigation tree. Visually, the frame application surrounds the device manufacturer’s DTM. Like opening a web page from a navigation tree in their ‘favourites’, FDT users can navigate down a navigation tree listing the field device tags, click on one and open the device vendor’s DTM inside the frame.

Like a web page that lets us interact with an online booking system or shopping service, the device DTMs allow users to interface with field devices in a wide variety of ways. The device DTM designer can create a graphically rich user interface that does virtually anything possible in an advanced interface.

The third part of the technology, the communication DTM, provides a standardised communication API inside the PC, interfacing between the device manufacturer’s DTM and the host system’s specific driver that handles pass-through communication from the PC down to the fieldbus interface card.

Figure 2: Relationship between device DTM and comDTM.

The host system supplier and each provider of a communication protocol interface provide a communication DTM for each supported fieldbus protocol and other protocols. This means that any proprietary protocol could be represented by the manufacturer in a comDTM instance. As such, proprietary service protocols - to support firmware upgrades for instance - can be integrated into a plant-wide asset management system if covered by a comDTM. The comDTM manages the details of the PC, network, interface cards and pass-through protocols of the host system, making them transparent to the device manufacturer’s DTM. This relates back to the internet analogy, where ideally the web page is not affected by the PC it is being viewed on, the brand of the network interface card in the PC or whether the PC’s communication is via DSL or 3G.

Here a fundamental difference between FDT and EDD technology exists. EDDL deals with the business of the device. FDT deals with the business of the device as well as how to reach it in the plant system. As such, FDT offers an end-to-end standardised system for integrating device support in a non-proprietary way.

Implementing the technology

Already, more than 70 major automation equipment suppliers support the FDT technology. As a consequence, DTMs are available for most common devices actively represented in the control and instrumentation market.

Having connected instruments to an industry standard fieldbus, such as Profibus, FOUNDATION Fieldbus or even HART, an FDT-based configuration tool like Endress+Hauser’s FieldCare can scan the bus, identify all the devices and then check the availability of the DTMs in the installed DTM library. The ‘live list’ of connected devices and their respective DTMs is automatically available for instrument configuration, troubleshooting and predictive maintenance.

In the event that a DTM for a legacy EDD-supported device is not yet available - as is presently the case for some HART and FOUNDATION Fieldbus devices - the interpreter DTM (iDTM) technology can be used to provide a bridge. The binary device support used by the HART foundation and FOUNDATION Fieldbus can be used directly by this DTM to provide full functional support. Devices supported by EDDs are identified in the DTM library along with those supported by proprietary DTMs. So FDT/DTM can be viewed as an inclusive platform.

FDT/DTM technology offers full device functionality (with no device or manufacturer dependencies); unrestricted choice of communication and topology components (with no protocol dependencies); full support for the user’s existing devices; and is now a truly open IEC standard.

A good FDT/DTM-based host system is characterised by flexibility, openness and adaptability. Endress+Hauser’s FieldCare is a good example of such a system as it can be readily retrofitted to any existing plant as it embraces and updates all existing devices and their software.

Setting the stage for the ‘smart’ plants of the future.

FDT/DTM is an enabling platform for the ‘smart’ plant of the future because it allows intelligent field devices to communicate seamlessly across different networks and interact with various management systems within the plant using this open technology. The data collected by these systems from the instruments and other assets in the plant can be used to schedule maintenance and even manage spare part inventories - by interfacing with other systems such as ERP - thus keeping maintenance costs to a minimum. Preventive maintenance can be implemented, avoiding costly plant downtime due to breakdowns. Spare part inventories required for plant maintenance can be minimised by ordering replacement parts only when they are required.

Connecting to the plant via a secure web interface, users can also diagnose problems in the plant at device level. This means that a maintenance technician can assess a problem with an instrument from their office and come to site with exactly the right spare parts to rectify the problem quickly and efficiently.

Endress+Hauser Australia Pty Ltd
www.au.endress.com