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The Power Is In Your Hands

HART Communication Foundation

Keywords: process automation, process safety management, automation engineering, process automation technologies, industrial automation and industrial automation system

Looking for a Digital Field Network? With HART, It’s Right in Front of You

T BRITISH PETROLEUM’S PTA (Purified Terephthalic Acid) PLANT in Wando, S.C., managers are facing a dilemma familiar to their counterparts at thousands of manufacturing facilities throughout the country: do more with less.

“BP is investing heavily in plant construction in China, so our objective is to lower costs and increase our availability. We need to use what we have and use it better,” says A.J. Lambert, an instrument and electrical reliability specialist with BP.

One way plant personnel are achieving that goal is by using a previously underutilized technology that is providing them with a remarkably detailed view of conditions throughout their plant and the ability to reduce asset management/maintenance costs.

The “silver bullet” that’s generating these benefits: the HART Field cCommunications protocolProtocol. “Through the use of HART diagnostic information, this BP plant is saving approximately $300,000 per year in just maintenance and production costs alone,” says Lambert.

Feel the Power
Of course, not every plant will attain such dramatic results, but most users can achieve all, or nearly all, of the functionality they seek by tapping into the proven power of the HART-enabled field devices they may already own. As a result, most of the benefits they achieve through the use of HART drop right to the bottom line. Few automation projects are as easily justified economically as that.

HART’s exceptional value to process manufacturers lies in its ability to simultaneously communicate an instrument’s primary variable via a standard 4-20 mA analog signal and and up to three secondary valuesadditional process variables and plus diagnostic information via digital signals on the same wire. Initially, HART was initially embraced by maintenance staffs who were delighted to be able to use handheld communicators and calibrators, such as those made by Meriam Process Technologies or Emerson Process Management and , and take them into the field. All they had to do was attach them to any HART-compliant instrument--regardless of manufacturer–and they were immediately able to retrieve critical information about an instrument’s condition, its health and its range, as well as perform calibrations, document them and obtain much more digital information besides.

Since then, manufacturers have developed a wide range of new intelligent products and added HART capabilities to existing ones, providing even greater benefits to a broader base of users. For example, field device makers such as Siemens differentiate themselves by communicating additional HART data that are unique to the company’s instruments. Siemens pressure transmitters have the ability to monitor and store data on the highest and lowest pressures experienced by the entire instrument, the instrument’s pressure capsule and its electronics, says Lou DiNapoli, marketing manager for the company’s pressure and temperature transmitters.

“All users have to do,” says DiNapoli, “is use a HART handheld device or our Device Description Language-enabled Process Device Manager (PDM) software to get that information, which is highly useful in diagnosing process problems. If you use someone else’s equipment and software, you just need the Device Description for our instrument.”

Sophisticated Asset Management
In recent years vendors have developed sophisticated asset management software packages, including Yokogawa’s Plant Resource Manager (PRM), Siemens’ PDM, Emerson Process Management’s AMS and Honeywell’s Asset Manager PKS, that enable maintenance engineers to view, track and analyze the condition of instruments remotely. In this situation, data from a device is split into separate analog and digital signals. The analog signal, carrying the primary variable, is routed to the control system, while the digital secondary values and diagnostic data are conveyed to the asset management systems.

Asset management systems and their ability to use HART data are proving enormously beneficial as numerous users will attest.

BP’s Wando plant started tapping the full potential of HART about five years ago, when it installed Emerson Process Management’s ValveLink software to gain diagnostic information from its approximately 125 most critical control valves. Among the areas in which the plant has cut costs is in valve maintenance during planned shutdowns.

“Before using HART, we would pull out 35-50 valves for maintenance during shutdowns every two years,” says Lambert. “There might have been a work order or some concern about a particular valve, but we really didn’t know what might be wrong with it. As a result, we’d spend a lot of money and time. Now, with more information from ValveLink and HART, we pull only five or six valves during a shutdown. And we have a lot more information about why we’re pulling it. Our diagnostic system can show us when a problem assumed to be in a valve really isn’t, but is perhaps somewhere else in the process. In other cases, we’re able to see potential problems in valves before they become serious.”

A senior engineer for field instrumentation with another  major oil company refiner says that digital HART instrument data, routed back to the refinery’s asset management system, has enabled it to improve its processes as well as realize savings on maintenance.