HART-IP – Enabling asset optimization in the process industry

The digitization of field devices in the process industry, the growing importance of predictive maintenance and the increasing possibilities offered by centralized field device configuration in modern asset management systems have all paved the way for the expanded use of digital communication protocols like fieldbus and HART. At the same time, WirelessHART has become established worldwide as the leading wireless protocol for process applications. When implementing WirelessHART gateways or when adding HART multiplexers to an existing infrastructure, HART-IP provides a new standard protocol ensuring efficient integration. HART-IP also enables easy integration of HART data into asset management applications.

Intelligent HART devices support centralized configuration as well as diagnostic and battery monitoring

The process industry is considered rather hesitant when it comes to implementing new technologies. Still, leading technology organizations such as FieldComm Group, ODVA and Profibus & Profinet International are forecasting a rapid increase in the use of Industrial Ethernet in the process industry. They expect Ethernet to be used increasingly instead of RS485 in plants, while Ethernet-APL will eventually replace 4-20 mA. The FieldComm Group (FCG) responded to this trend back in 2012 by introducing the HART-IP Ethernet protocol. HART-IP offers the possibility to tightly and efficiently integrate WirelessHART gateways and HART multiplexers into the control systems of legacy or new process plants. HART-IP also enables simple vertical data integration from field devices to the control room. The HART protocol can be run over Ethernet, Wi-Fi, or other network media without sacrificing the detailed device setup or diagnostics information offered by existing networks. In addition to providing access to a device’s process variables, the protocol also supports device parameterization and advanced diagnostics. HART-IP will therefore play an important role in enabling the Internet of Things in process plants.

HART-IP provides information in wired and wireless devices to higher-level applications (SCADA, CMMS, DCS, ERP, etc.) independently of the transmission media

The system integration challenge
System integration using traditional PLC protocols is increasingly reaching its limits. Traditional hardwired transmitters often deliver only a single variable – the process value. Mapping a single variable per device from a PLC or RTU Modbus register to process visualization software is manageable. However, devices usually provide multiple measurements, control signals and feedback with up to four dynamic variables per device, each with an associated status. For instance, temperature transmitters might provide two or more temperature values, pressure transmitters both current pressure and differential pressure, acoustic transmitters both noise and temperature values, or vibration transmitters not just vibration but also acceleration and temperature figures. Mapping all those dynamic variables delivered by such multi-variable devices in Modbus registers or OPC groups and items would be time consuming and error prone. Modbus registers and OPC items work for process variables, but are not suitable for intelligent device management (IDM) software as part of asset management systems. Intelligent HART devices, on the other hand, support centralized configuration as well as diagnostic and battery monitoring. While a handheld field communicator can be used for device configuration and troubleshooting, it is impractical for plant-wide deployment. Intelligent device management software is a better solution for plant-wide networks.

HART-IP enables the provision of HART information to higher-level applications

HART-IP enables end-to-end device communication
As diagnostic data become more important and field devices in process plants more digitized, an ever increasing number of users and system providers are moving their focus to HART-IP. HART-IP enables complete plant-wide, large-scale solutions and offers a high degree of interoperability between devices and applications. The protocol runs over IP-based networks such as Ethernet and Wi-Fi and works over UDP (User Datagram Protocol) and TCP (Transmission Control Protocol) with IPv4 (Internet Protocol Version 4) or IPv6. The HART-IP application layer is based on the same commands as 4-20 mA/HART and WirelessHART. In contrast to serial data transmission, process and IT data can be transmitted over a common medium. There is a large address space with an almost unlimited number of participants available, and cascading switches enables the creation of huge networks. Furthermore, larger amounts of data can be transferred efficiently and different transmission media (copper, optical fiber, radio) can be combined.

HART-IP is a high-level application protocol independent of the underlying media and works over standard Ethernet (IEEE 802.3), both copper and fiber, as well as Wi-Fi (IEEE 802.11) equipment. It is thus suitable for use with standard infrastructure components like LAN switches, routers, access points, cables and connectors. HART-IP can also utilize existing network structures with redundant Ethernet media as well as mesh or ring topologies, or Power over Ethernet (PoE). Various speeds like 10 Mbit/s, 100 Mbit/s and 1 Gbit/s are supported.

Using IP-based communication enables multiple protocols to share the same network, each protocol with a specific application. As a result, HART-IP coexists with IT protocols and other industrial Ethernet protocols such as HTTP, Ethernet/IP or PROFINET. There is no need for dedicated infrastructure. The use of multiple clients and servers is also supported, enabling multiple controllers and software applications to access the data in one or more gateways or multiplexers over the same network.

HART-IP can be employed for devices using Ethernet and for HART-IP backhaul networks in HART multiplexers. It is used in Intelligent Device Management (IDM) software as part of asset management systems as well as in OPC servers to access data in 4-20 mA/HART field devices. Specialized applications such as software for monitoring steam traps or machinery health already use HART-IP to access device data. In the future, control systems and automation solutions are expected to provide HART pass-through over HART-IP. HART-IP devices for seamless vertical integration in plants are also conceivable. Some devices, such as flowmeters, already support Ethernet.

However, many devices in process plants, such as transmitters, analyzers or valves do not have Ethernet connectivity – nor will they in the foreseeable future. These devices will probably continue to use 4-20 mA/HART, fieldbus or WirelessHART. HART-IP is not yet ready to replace these protocols at the device level, and so far would not be suitable for many reasons:

- The reach of copper Ethernet is too limited.
- Fiber optic Ethernet provides no power.
- Power over Ethernet (PoE) so far is not intrinsically safe.
- Given that there are thousands of transmitters and valves in a plant, the large number of LAN switches to be installed would not make sense economically.
- Fiber optic Ethernet makes device replacement and subsequent calibration impractical.
- TCP/IP requires IT departments to be involved to ensure cybersecurity.

Advanced Physical Layer paving the way for Ethernet in process plants
With the breakthrough of Ethernet Advanced Physical Layer (APL) expected in the next few years, however, the niche existence of Ethernet at field level could come to an end. Instead, the technology could find widespread application as 4-20 mA could be replaced by purely digital 2-wire Ethernet APL (Advanced Physical Layer). APL is Single Pair Ethernet (SPE) and circumnavigates the limitations of 4-20 mA. APL describes a physical layer for Ethernet communication technology that was specifically designed to meet the requirements of the process industry. Ethernet APL was developed because of the need for high-speed, long-distance communication, the need to provide power and communication signals over a single 2-wire cable, and the need to ensure safe operation within potentially explosive environments. As part of the widely used Ethernet standard, which was developed specifically for sophisticated industrial applications, Ethernet APL offers a high level of robustness for extremely reliable operation.

Ethernet has long been established as the standard communication solution in the information technology domain. Industrial Ethernet is the common name for the variant of this standard used in the manufacturing and process industry. Ethernet APL was developed to provide the previously missing link. It extends unified Ethernet communication all the way to field instrumentation, paving the way for the use of communication protocols such as HART-IP, Ethernet/IP and Profinet.

HART-IP is expected to be predominantly used within the plant perimeter. If the protocol is used beyond the plant perimeter via an Internet connection or Wi-Fi, security measures must be employed to protect the data during transport (such as firewalls, VPN tunneling, Secure Socket Layer (SSL), and remote authentication). The standard encryption protocols will continue to evolve and HART-IP is designed to be able to adapt to new versions.

Expanding the traditional automation pyramid through Namur Open Architecture
NAMUR Open Architecture will be yet another driver promoting the use of HART-IP. Although the structure of the classic automation pyramid offers a high level of operational reliability, it lacks the flexibility required for the implementation of new technologies in connection with Industry 4.0 solutions. This is why Namur has introduced the NOA (Namur Open Architecture) concept to expand the existing structure with an open OPC UA interface. The Namur Open Architecture concept offers the possibility to export data from the previous automation world to the systems world for monitoring and optimization purposes, leaving core automation tasks largely unaffected. Alternatively, a second communication channel can directly access information from existing field devices. In view of this, more and more users and system providers are now focusing on HART-IP as an additional open interface.

HART-IP supports Industry 4.0 applications
HART-IP is the most suitable backhaul network for WirelessHART gateways and HART infrastructure components since both have the same application layer, which eliminates time consuming and error-prone data mapping (e.g. for Modbus or OPC).

HART-IP is easy to deploy because it uses Ethernet infrastructure already available in most plants. Existing intelligent device management software can be upgraded to the latest version supporting HART-IP and the underlying WirelessHART gateways.

While HART-IP might not revolutionize the entire process industry, it will make a significant contribution to promoting and, crucially, simplifying the exchange of data and information in process plants, thereby meeting the basic requirement for implementing Industry 4.0 applications.

With its smartLink DP product, Softing offers a NOA-compliant gateway that collects data from HART devices via PROFIBUS remote I/Os and makes it available via OPC UA in accordance with the companion specification. Moreover, a HART-IP server integrated into smartLink DP provides transparent access to HART field devices via Ethernet. In the future, it will be possible to use any HART-IP client, such as Emerson's AMS Device Manager or ProComSol's DevComDroid Android app, to set parameters, monitor and evaluate HART field devices via this open communication standard.

Features of HART-IP technology:
- Easy to implement by using existing Ethernet infrastructure
- Standardized use throughout the process plant
- Intelligent device management via Ethernet or Wi-Fi
- Company-wide access to device data and condition-based diagnostics information as well as process data with no mapping required
- Supports proactive maintenance strategy by providing fast access to diagnostics data
- Compatible with standardized encryption protocols for data transport

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