By Harry Forbes

The vast majority of the tens of millions of field instruments in process plants today support the HART protocol. Though dating from the 1980s, HART can provide a number of important and valuable services for end users if they were Integrating HART Field Devices. These include device diagnostics, calibration, rescaling, etc. Unfortunately, almost all these instruments are installed in systems that do not support continuous use of HART protocol, so end users only use these features when manually maintaining individual instruments.


Yet the relentless pressure of business and the “graying” of the workforce continue to thin out the numbers and expertise of plant staffs. Business pressures result in directions from management to “do more with less,” or in other words, maintain or improve production asset performance with fewer human and financial resources.  If this were not enough, there is also a stream of new business initiatives enabled by new IT and collaboration capabilities, such as those represented by the Industrial Internet of Things (IIoT) or Industry 4.0. Yet new technologies are very slow to reach installed process instrumentation.  Indeed, much of this equipment has not changed significantly in many years.

An obvious way to extract additional value from the installed instrumentation and from the measurements it delivers is to capture and integrate the information available via the HART protocol and use this information to improve production performance and reliability. But in the era of doing less with more, end users require simple and low-cost solutions for capturing and integrating this data.

Requirements for Integrating HART Field Devices

End users should be aware of several requirements when they begin to capture and integrate the value of information now hidden within HART instruments. Here are the top few:

Industrial hardware: When new hardware must be added, end users will look for convenient locations.  Often, these will be in the field where the hardware will be exposed to temperature extremes, hazardous vapors, and the like. So certified industrial hardware suitable for these locations is necessary. End users should standardize on some form of this.

Modularity and scalability: Since installation at multiple locations will be required, the hardware should not only be industrial but also highly modular and scalable.  Some locations will have only a few measurements, while others may have dozens. It would be helpful to find a common solution across all these situations.

Ease of deployment and maintenance: Ideally, deploying new instrumentation infrastructure should be done without adding to the current burden of maintenance. In fact, to make business sense, new instrumentation infrastructure should reduce the existing maintenance workload if possible. Furthermore, the new instrumentation infrastructure should be simple to deploy, requiring either “no touch” or a very gentle touch for installation and startup and minimal local maintenance during its operating life.

Ease of integration: It is not enough simply to gain access to diagnostic data and the like from instruments. The data and the operations need to be easy to integrate within the existing automation and information infrastructure and within the existing work processes that the operations and maintenance personnel are already familiar with.

Security: Any new infrastructure should enhance asset and network security rather than reduce it. Legacy networks such as HART have the benefit of requiring physical access to the device or its cabling to perform any action. This is not true for HART IP, so security becomes an important consideration.

Integrating HART Field Devices Using Industrial Gateways

Today end users can integrate installed HART devices using industrial gateway products such as the recently enhanced Phoenix Contact “GW PL” products (see figure). This product line consists of a small family of modular units, all DIN rail-mounted and field-installable.  An installation consists of a head end unit coupled with one or more expansion modules that plug together on the DIN rail to form an integration point for between four and 40 HART devices. Deployment and commissioning can be done from anywhere once the device’s IP address is assigned. End users can configure the IP interface either before or after installation in the field. Once the device is on the IP network and wired to the HART instrument loops, any operation can be performed remotely.

Phoenix Contact GW PL Industrial Gateway Products Support Multiple Protocols Integrating Hart Field Devices hfhart2.JPG

Options for data integration include HART IP, MODBUS TCP, Profinet, and Emerson AMS. These options can be selected at any time from any location. If the associated instrumentation involves critical safety functions or requires local access only, the installation can be configured with additional equipment that serves as a “data diode” to prevent remote users from issuing HART protocol commands.

Some Use Cases

Now consider several use cases illustrating the potential value of this type of installation to capture and use device information that is often wasted today.

New critical measurements: A major process manufacturer experienced a loss of several million dollars in production due to the failure of a critical new unit of process equipment. As a result, engineers installed several dozen new field instruments to more closely monitor this critical unit. The new instruments were wired through field junction boxes each equipped with a HART gateway. The gateway served measurement and alarm information to the unit control room and enabled plant technicians to examine and service the new instruments via their existing device management software.

Remote maintenance: As part of its regular maintenance, a company was required to exercise actuators at dozens of remote locations. This work had been performed locally by technicians making maintenance rounds. With the installation of new HART gateways, testing could be performed remotely and did not require making rounds to the remote assets. This greatly shortened the time for testing, improved compliance, and freed technician time for other activities with greater business impact.

Integrating HART Field Devices hfhart3.JPG

Safety-related measurements: Instruments that are part of plant safety systems are generally not accessible through IP networks but instead require local access. However, measurement information delivered by these instruments can be extremely valuable. To access this data, one process manufacturer configured several HART gateways with small modular data diodes. The data diodes permit only outbound information and filter out remote commands.  As a result, the installation remains secure from remote tampering, but key measurements are distributed throughout the DCS and higher-level applications. The NAMUR organization envisions this type of insulation as part of its NAMUR Open Architecture. In this vision, critical control activity is undisturbed by its integration while the systems that integrate the information also cannot disturb critical process control functions (see figure).

Recommendations for Integrating HART Field Devices

End users should look first for business value to determine where and when to integrate HART measurements with advanced systems. An application with a strong business case obviously creates incentive for success.

A highly modular hardware platform could help here since it would enable common technology to be applied across both large and small installations, and across both field and less challenging physical environments.

Focus on critical measurements. Many process plants have thousands of HART instruments installed, all with hidden data. Integration programs should focus on the most critical 2 to 5 percent of measurements so that the integration program can deliver the highest value quickly.


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