Getting the Most From Plant Assets

An asset management system can help plants figure out that something’s about to blow before the equipment actually blows. Asset manager software applications can read device data through a fieldbus network to interpret and display the device’s problem before the device fails and shut down the process.

One such fieldbus with device information protocols is Hart, from the Hart Communications Foundation. The power plant at The Ohio State University, in Columbus, Ohio, was using Hart to communicate with its instruments at least 10 years before the plant took the extra step and installed asset management. It previously used only the 4 to 20 milliamp (mA) communication capability available through Hart without tapping into the rich device information residing in the network protocol. “I didn’t even know what asset management was until four years ago,” says Jerry Lowery, a controls systems engineer at the University plant. “In 2004, we upgraded our software and added asset management.”

The asset manager lets plant engineers know how each individual device is working and whether it’s positioned or calibrated correctly. “When an instrument has an issue, we know immediately, especially a valve position,” says Lowery. “Now we can replace it before it breaks. In the past, we did nothing. We wouldn’t catch it until the yearly evaluation.”

Another benefit from the fieldbus network and asset manager is the ability to use devices from different manufacturers. “We use a lot of different vendors for our field devices,” says Lowery. “But as long as we’re using a vendor that uses a standard DD (device description), we don’t have a problem.”

If it ain’t broke...

使用现场总线networ资产管理系统ks to monitor and manage instrument behavior. This system allows maintenance personnel to watch the instrument as it streams data to the user interface. The engineers can see how the device is working and keep a history of the device’s behavior. The system can actually match the device behavior with its history to determine whether the part is at any risk of failure. In the past, plants would typically schedule a maintenance shutdown and replace all devices whether they were about to fail or not. With asset managers, operators are shifting from preventative maintenance (replacing instruments, broken or not) to predictive maintenance (replacing devices only when they’re as risk of failure).

Smart devices have the capability to alert users of their problems even without the use of an asset management system. The asset manager, however, can take the device data a step further and present a detailed context of device data for plant operators. “Because these devices are smart, they can diagnose themselves and record this diagnostic information,” says Tim Sweet, manager of product management for Asset Management, a division of process controls vendor Honeywell Process Solutions, in Phoenix. “But that’s only half the game. With bus technology, those diagnostic status messages can be communicated back to a centralized computer system, which can synthesize the data so that it is meaningful to the maintenance and reliability engineer.”

Asset managers can help plant operators absorb the flood of device data and view it in a comprehensive format.
“Take a medium-size refinery that is producing 150,000 barrels per day. That plant is responsible for about 2,000 controls,” explains Wil Chin, analyst at ARC Advisory Group Inc., in Dedham, Mass. “You can’t manage all those loops without help.
The asset management system is able to look at all the devices and check on the one with a possible fault. It can look at that device’s history and see its trends. It can see the one transmitter that is reading different from the others.”

The asset management system is able to monitor process operations while also looking at maintenance needs and potential problems. “Asset management has two main focuses. One is the management of the assets and the other is maintenance,” says Moin Shaikh, consultant at Siemens Energy & Automation Inc., the Alpharetta, Ga.-based automation vendor. “When it’s used to manage the assets, the system offers efficiency advantages. We have customers who don’t want any unplanned downtime. So the asset manager uses the fieldbus network to monitor for anything that might cause downtime.”

One of the goals of the asset management system is to help the maintenancedepartment shift from preventive maintenance to predictive maintenance. That means fewer shutdowns and an end to replacing parts that are functioning well.

For maintenance engineers, the asset manager presents the device data in the context of its history, including any instances of problems or failures. “Virtually all process automation is coming down to accurately controlling a valve. If the automation doesn’t control the valve well, the process is shut down,” says Charlie Piper, Foxboro Automation fieldbus product manager at Invensys Foxboro, a process controls vendor in Foxboro, Mass. “The asset manager will tell you if the device is slow to respond and let you know if the device has a history of problems.”

Managing acronyms

The fieldbus network carries the data from the device to the user interfaces. The main fieldbus protocols include Foundation Fieldbus, Hart and Profibus. The three main standards organizations have worked together on their protocols so device data can be read by any control system, allowing plants to use devices from different vendors.

There are a number of acronyms associated with fieldbus technology. DD is the device description. This tells the network what type of device is connected. DDL is the device description language that communicates the “smart” information coming from the device. If the device is failing, it communicates this information in DDL.

A couple of years ago, the Fieldbus Foundation, Hart Communication Foundation and Profibus International collaborated to come up with EDDL, the enhanced version of DDL. EDDL was created for advanced visualization of intelligent device information to maintain the integrity of DD across all three communication technologies.

EDDL was also designed to include improved user interface with the support of menus, windows, tabs and groups with the added user tools of graphs, trends, charts and dial indicators. Instrumentation and control system vendors participated in the validation of EDDL, with the goal of making the language vendor-independent. The idea is to allow users to choose best-in-class instruments that can be used on the network no matter what control system the plant is using.

The asset management system takes the information coming from the devices through the fieldbus network and makes sense of it in the context of the individual plant. Sometimes called plant asset management (PAM) systems, these tools organize the network information according to the user’s needs. “Asset management systems allow a change in philosophy. You have better information about the device, so you know what will happen if you don’t change the device next week,” says Ron Helson, executive director, Hart Communication Foundation, in Austin, Texas. “It allows you to take advantage of that information and take action before a failure disrupts your plant.”

For maintenance, PAM systems answer questions such as, “What equipment may fail if it doesn’t receive maintenance?” The maintenance view will also show wear or faulty behavior of individual devices. For operations, PAM answers questions such as, “To what extend can I increase output without risking quality or safety problems?” The operations view also includes information on adjustments that can be made to prolong the life of the assets.

A PAM system can also include an asset information register, which shows how the asset fits in with the entire plant system, and a data harvester, which can access historic information on the behavior of individual devices. The data harvester can also monitor asset behavior such as vibration, displacement and electrical functions.

The data from the harvester can move through the condition monitor, which holds the baseline condition. If the data doesn’t match the model, the operator can be alerted. Finally, a PAM system can include an asset health analyzer that acts on exceptions found in the condition monitor, and classify the exception by type and need, such as potential problems with lubrication, vibration or process discrepancies.

Asset management systems offer plant operators a new look at their process operations. As well as using the data for maintenance, operators are also starting to use device data as a tool for optimizing plant equipment and operations. Because the asset manager can track plant data and store history, operators can use the data as a match against an idea model of plant operations. Through tweaking the devices, operators can squeeze more throughout out of the equipment, while closely moni-toring the potential for stress and thus avoiding device failure.

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