Justifying HART investments to management

Fritz Geiger, a systems product manager with Siemens, notes that HART Device Descriptions enable users to store all or nearly all of their instrument data in a single database, thus improving organization, reducing expenditures on multiple pieces of equipment and software, and making more efficient use of personnel.

“This provides high benefit for the user,” says Geiger. “He may have thousands of instruments and has to keep all of those different ranges and parameters updated. The best way to do that is to have all of the information available in a single database.”

Sasol, an international chemical manufacturer, can testify to the value and benefits of HART based on its use in its South African solvents operations. In 2000, as part of the planning process for construction of a butanol plant, the company set as goals the detection of field instrumentation and valve problems before they could cause production loss; migration from run-to-failure maintenance mode to predictive maintenance strategies; a reduction in control valve maintenance expenditures; and improved change management.

Sasol saw HART-based asset management as the means for achieving these ends. Among the benefits the company realized through the use of HART-based asset management just in the past two years are savings of nearly $2 million on prevention of plant trips, the avoidance of unnecessary repairs, and detection of faulty or poorly optimized valve positioners.

THE HART DIFFERENCE

Two Simultaneous Communication Channels

• 4–20mA channel—fast, robust & reliable
• Digital two-way communication channel for device status, diagnostics, alerts, etc.

35–40 Data Items Standard in Every HART Device!

• Device Identification—Calibration Data
• Process Variables—Diagnostic Alerts

OBVIOUSLY, no two plants are alike, and results that each can achieve through use of HART can vary widely. Based on their experience working with a wide variety of users, systems and instrumentation vendors have come up with a number of implementation tips to consider and pitfalls to avoid:

Implement Solutions Gradually
Emerson’s Cobb notes that HART can be effectively implemented gradually, by tiers, making it easier to budget investments over a long period.

”At the low end of investment, you can stay offline and simply monitor loops on a manual basis periodically. This can be done in the field with a handheld communicator or by hooking up a PC equipped with asset management software, including data on all your instrumentation,” says Cobb. “At the next level up, you can establish continuous monitoring via a separate asset management system. And, beyond that, if your plant has invested in a control system with HART I/O, you can bring the secondary variables directly into it.”

Rely on Existing Equipment
Rely as much as possible on existing equipment says Steve Todd, marketing director for Moore Industries, which manufactures HART multiplexers. "We've found that customers that stand to gain the most from HART technology are the ones that can leave as much existing equipment in place as possible, yet still make significant, cost-effective process improvements. For example, if a customer wants valve position feedback at the control room, he can go the traditional route and run additional wiring back to the control room that provides this data. This gets expensive fast. A second alternative, though, is for the customer to leave everything else alone, and install smart HART controllers on the existing valves. Then, extract the stem position data from the HART digital data using a HART interface instrument installed in the control room.”

Demand Interoperability From Vendors
“While HART is a very open protocol, not every company subscribes to it,” says Honeywell’s Raghavendra. “Consequently, buyers should make sure from their vendors that the field device and/or system fully complies with the protocol as defined by the HART Communications Foundation. Customers also should encourage their vendors to register their devices with the foundation.”

Be Specific About Your Goals
Be specific about how you want HART to meet your needs, advises John DuBay, instrumentation product manager for Meriam Process Technologies. “Predictive maintenance is a great story, but many end users aren’t sure what diagnostics they’re looking for. If you ask them about the specific diagnostic capabilities they’re interested in, they’re not always sure.”

Provide Easy Access to HART Data
To achieve the benefits of online configuration and diagnostics, operations and maintenance personnel need to cooperate. However, that situation often is the exception rather than the rule, says DuBay. “Not many operators are eager to open up access to their maintenance crews because they’re fearful that devices could be reconfigured incorrectly or by accident.”

Know Where the ROI is Coming From
Masoneilan Digital Product Specialist Sandro Esposito advises that users should not expect to get substantial maintenance-related ROI from new HART-enabled digital valves. “The big rate of return is on the existing valves,” says Esposito. “You can graph a valve's performance over time and see that it plateaus at a high level of performance when it's new. You want to know where's the drop-off from that plateau, and how steep it is.”