For over twenty years, HART communication has been the largest communication protocol in use in the process industries. There are over 35 million HART instruments installed. HART is simple, reliable and secure. Yet still many HART users are only using only the calibration and configuration capabilities that are the basic features of the protocol.
This is changing, though, and changing fast. As the requirements of end users for more connectivity, more sensors and devices and better maintenance capabilities to enhance production efficiency increased, HART capabilities have kept up with these needs.
But HART has always had the capability to do far more than just calibration and configuration with a hand-held device or a PC. HART was designed from the beginning to connect to control systems and asset management systems.
In order to prosper in the continuing uncertainty of 21st-century business, end users are discovering that they need to have a better grasp of their processes, get faster, more detailed diagnostics, and cut expenses while continuing to improve performance and productivity. When they look at their existing plants, many are surprised to see that they already have the ability to do those things using their existing HART-enabled sensors and devices.
WirelessHART extends the HART protocol for new and nontraditional sensors, such as on/off valves and steam trap monitors. WirelessHART has broken the speed-barrier with one-second update rates and has improved the capability of the HART protocol to be used in closed-loop control.
Most modern control systems are now provided with native HART interfaces. Several vendors provide I/O systems with embedded HART communications. WirelessHART provides, from the gateway, Modbus and Ethernet connectivity to any control or maintenance system, and HART via OPC is in common use.
Ten Essential Best Practices
Leading plants leverage HART communication as much as they can. Here are the ten essential best practices common to all leading plants and their use of HART and WirelessHART. We are going to look at what several leading plants have done with HART.
- Networking and communications protocols are life-cycle solutions.
You cannot every so often rip and replace your networks. This is as true for the plant LAN as it is for the I/O. When designing a network solution, picking the communication protocol is critical for long-term success. In 2005, the MOL Danube Refinery (the 2010 HART Plant of the Year) embarked on a comprehensive maintenance strategy, using HART. The goals of the strategy included:
• Creating an online analysis, transmitter and assembly diagnostics system
• Creating a laboratory and field calibration support system
• Improving plant availability and reduce shutdowns
• Reducing maintenance costs
• Reinforcing CAPEX project support with appropriate assets in the appropriate place.
Having decided to standardize on HART and WirelessHART as the common field device protocol, MOL is able to leverage the functions in the protocol over the life cycle of the 30,000-plus HART devices they already have, while adding new devices and new uses.
- Solid planning is essential. Your networks can't grow like Topsy.
One of the most significant benefits of standardizing on HART communication is the flexibility of the protocol. Not only is it backward-compatible to early HART devices, it is the same protocol, whether transmitted over 4-20 mA loops or over Modbus or Profibus or Ethernet or wirelessly. HART has grown and developed and added new features expressly designed to work together seamlessly, interoperably and interchangeably. Through it all, HART has remained simple, reliable and secure.
MOL designed its maintenance system to integrate HART-based device alarms and maintenance alerts all the way to the SAP system. The only way to do that is to plan. Starting with HART makes that planning much simpler. Bruce Power, on the shores of Lake Ontario in Canada, the largest nuclear power plant in North America, planned a redesign of the feedwater heater system to eliminate steam hammer. Using a comprehensive valve control solution based on HART, it was able to run the plant up to full power without the heaters causing alarms and hammer.
- Maximize resource availability.
Shifting from preventive to predictive maintenance strategies is the clear choice for maximizing resource availability. Shell Canada Ltd.'s Scotford Upgrader Expansion (located near Fort Saskatchewan, Alberta) has several thousand instruments, of which about 33% are HART-enabled devices. That's still thousands of instruments, and, as Andy Bahniuk, Shell's instrumentation technologist, points out, the company is using 26 different device types provided by several suppliers, including Emerson Process Management (Rosemount), Endress+Hauser, Krohne, Magnetrol, K-Tek (ABB), Fisher Valves from Emerson Process Management, Ohmart nuclear level gauges from Vega International, and Metso valve positioners.
This alphabet soup of different devices and vendors interoperates perfectly—because they are all HART. Shell Canada now uses HART devices everywhere except where a HART device simply is not available. Bahniuk says it is because HART is so easy and is plug and play.