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IF YOU'RE one of the thousands of process automation professionals around the world burdened with an older, maybe even antiquated plant—listen up. We’re not just talking to you if you live in the U.S., the rest of North America, or Europe, either. There are older, out of date plants everywhere. They exist in Japan, India, and China, too. So in this article, we are talking to YOU!
What’s Asset Management?
You may be confused when people use the term, “asset management.” It isn’t an accident. It’s a buzzword like “synergy” or “integrated.” Some vendors use it to mean an operations and maintenance function, like predictive maintenance. Others use it to mean process optimization, using a plant’s control system and field devices. The term is in serious danger of becoming whatever the vendor wants it to mean, when he’s explaining to you why you can no longer get along without it. However, both asset management and asset optimization can make you a lot of money, if you play your cards right. In the next few pages, we’ll show you how to draw a full house with asset management.
The simplest way to look at this is as a series of steps to improving your plant’s availability (what we used to call “uptime”). Even though it’s clear that it’s a very costly practice, many plants still operate on reactive maintenance—when it’s broken, then they fix it. The reason this is so costly is clear from the “after incident reports” we’ve all seen. The failure of a $3,000 level sensor shuts down an entire batch reactor train, costing the company $50,000 per hour in lost production, for days, while the device is repaired or a new one is procured.
This has led companies to try predicting where problems will occur, based on history, and allows failure-prone devices (valve, motor, sensor, controller, etc.) to be replaced during scheduled maintenance shutdowns so they don’t die during a production run.
This isn’t cheap either, and the costs of throwing away perfectly good used equipment because it <ital>might<end ital> fail between two scheduled maintenance periods can run high, especially if you’re talking moderately large control valves or devices of that ilk. Auditors and other corporate financial officials have real trouble understanding the economics of this, too.
Predictive Maintenance—The Heart
The most progressive companies are now attempting to apply predictive maintenance, which seeks to determine when a device is likely to fail, based on its operating characteristics, and replace it just before failure. The idea is that if enough data on the performance of the device is available, it becomes relatively simple to determine when it will fail. Data, including vibration, pressure drop, deviation from accuracy, observable wear, increased power consumption and so forth, can be used to determine when pumps, motors, valves, or sensors need to be replaced. This immediately reduces the number of devices that require replacement every shutdown, which saves money that would otherwise be spent unnecessarily. It also reduces unplanned downtime by spotting and correcting potential unplanned shutdowns before they occur.
This is done by collecting a sizeable amount of data, and looking at the trend plots. In Figure 1 below, you can see where the vibration data being collected (by hand or automatically) from a motor train (pump, gear reducer, and motor) goes rapidly up the chart. This indicates that there’s an approaching failure point. The ability to see failures before they occur is key to predictive maintenance.
FIGURE 1: VIBRATION DATA CAN PREDICT FAILURE FOR MOTORS AND PUMPS
You can see the difference between a worn motor and a new one, and you can see the point at which the vibration trend signals a real problem coming real soon.
Wade Howarth, automation manager for Cargill Health and Food Technologies in Eddyville, Iowa, is saving money with a predictive maintenance program. “We’ve been able to shift our focus to “prevent” from “correct,” and the documented savings are significant,” he says. “We intend to keep exploiting the predictive maintenance environment and avoiding unexpected stoppages.”
So what’s keeping many plants from moving in this direction? Partly, it’s the perceived startup cost and time to implement the system. As Howarth says, “Our work practices have certainly changed.” Sending already overworked operators and maintenance personnel around the plant with clipboards in a sort of “dance of the human dataloggers” is seen as impossible by most, and incredibly burdensome by the rest.
|FIGURE 2: MACHINERY HEALTH MONITOR|
Top-of-the-line Emerson CSI machinery health monitor crunches the data internally, and sends back reduced data, while other systems send raw data back to the host for processing.
Companies have responded by providing optimized dataloggers, and even locating computing power out in the field to automate the process of datataking. For a look at one of the most comprehensive of these, see the Emerson CSI machinery health monitor in Figure 2. However, at $6,000-$8,000 per motor train, this solution is out of reach for pervasive preventive maintenance, even at very large companies. If you have 500 motors in a plant, it’s prohibitive to instrument all of them.
Lower-cost machinery health monitors are beginning to be offered. The difference between these and the more comprehensive ones, such as the CSI or GE Sensing versions, is generally that there’s less intelligence embedded in the lower-cost units. This is leading to two basic models for machinery monitoring. One, typified by the Emerson CSI units, puts intelligence at the device level, and only data that has already been reduced goes to the control system or the online asset management system. In the other, raw data is sent to the control system, which performs the analyses there.
Data Into Information?
So, we’ve gotten to the point where we all agree that predictive maintenance is a good thing, and that there are ways to automate data collection. How do we get from there to actually having the data in a location and format that makes it meaningful, and therefore, <ital>information.<end ital> That’s the problem.
The other problem is how to propose a project to your management without saying that you’ll have to put a lot of equipment, hardware, and software in at a large startup cost before you start saving a single dollar from predictive maintenance.
HART: The Missing Link
The HART protocol is installed in 20 million devices worldwide. That’s a huge installed base. Most people use the protocol for configuring and troubleshooting individual devices, and not much else. But that’s not the only benefit you can get from the HART devices you already have in your plant.
In 2004, the HART Plant of the Year Award went to the Cooper River facility then owned by BP. A.J. Lambert, instrumentation and electrical reliability specialist, reported then, “Before using HART to connect our field devices to our asset management system, we had a major shutdown every two years, and pulled out 30 to 50 valves. Now with more information, we pull maybe five or six valves, and we know exactly why we pull them.”
How does he know? His HART data, tied to his asset management system allows him to see the projected failure rates for his valves and controls.
“We’ve realized over $2 million in documented savings to date,” said Johan Claassen, E/I manager for Sasol Solvents, of Sasolberg, South Africa, the 2005 HART Plant of the Year winner, when accepting his award, “and will continue to enhance our use of HART and expand on its benefits in the future.”
There are literally dozens of companies offering some sort of software for asset management, from packages like Flowserve’s Flowstar.net to offerings from Invensys, Honeywell, Siemens, Rockwell Automation, and Emerson’s AMS product, which we’ve already discussed. Web-based Flowstar.net is interesting because it includes “an active partnering process” with Flowstar.net’s tool to help plant personnel gain the most use from the tool.
In other words, plants using Flowstar.net outsource their asset management functions to Flowserve’s personnel. As we’ve reported before (See “The Art of Asset Management,” CONTROL, Nov. ’04, and “Serving Up Asset Management,” CONTROL, Nov. ’05) there is a movement that’s captured the interest of overworked plant executives and hungry automation vendors alike to outsource maintenance and repair services to a vendor organization. Most large vendors, such as Rockwell, Emerson, Flowserve and others, offer this service to a greater or less degree. Such sophisticated asset management software, including Honeywell’s PKS Asset Manager, Siemens’ PDM, Yokogawa’s Plant Resource Manager and others, can even be used remotely through OPC.
There are even software packages, like Matrikon’s OPCVigilant, that are device manufacturer and fieldbus type agnostic. As long as the asset you’re trying to manage has an OPC driver built into its code, OPCVigilant, and any other OPC enabled software product, can extract the data from that asset, and assemble it in a form that can be used by nearly every control system and middleware (MES) vendor in the world.
Selling Asset Management to The Boss
A.J. Lambert suggests that you start small, like he did. His investment of approximately $10,000 generated more than $300,000 in documented savin gs by the end of the first year.
Experts like Lambert point to the ubiquity of HART devices, and suggest that you begin by identifying a device or set of devices with a high probability of failure. Start by grouping those assets into an asset management system. Once the payback from your initial project is proven, it should become easier to gain approval to add more devices to the asset management system. With the advent of HART Wireless (See Sidebar Story below), it will become even easier to do simple, small projects, and network them together one at a time.
Once you have the basic management of your assets under control, and you’re using predictive maintenance, it’s time to look beyond the device level, and see if you can better manage groups of assets. The next step is predictive maintenance based on the control loop as the asset to be managed, and beyond that, the process as a whole, considering itself as an asset.
Alireza Haji-Valizadeh, technology development manager at ControlSoft, says it’s extremely useful to treat the control loop itself as the asset, rather than the devices that make up the control loop. Once you start thinking that way, he suggests, it becomes rather easy to extend the concept to the entire plant.
“Looking at loops as a cut on automation hierarchy and as a component in a plant-wide structure can help to devise an effective predictive maintenance strategy,” stated Haji-Valizadeh in the December 2005 issue of our sister magazine, Plant Services. “We propose to extend this view of a loop to incorporate all levels of the automation hierarchy. As an example, consider a reactor temperature control loop.” In Haji-Valizadeh’s view, all of the components from the reaction, the sensors, heaters, device networks, PID algorithm, PLC and its programs, all the way out to the HMI and human operators themselves, are functional loop components.
Thus, the same condition-based monitoring that works for the lowest device and final control element layer can be applied to optimizing the process itself, loop by loop.
Now Get Started!
If you’re still operating in the mode of driving your plant to failure and then fixing what’s broken, you might try to look at a simple asset management project. Keep it small, keep it simple, and pick one with the potential of decent payback. You might get hooked on the idea of keeping your plant running by fixing what’s going to break before it actually does.
MOST PEOPLE think of HART, when they think of it at all, as a means to calibrate and set up field devices and valve controllers [See “HART 6: The Very Model of a Modern Calibrator?” in March '05]. It’s far more than that. It was envisioned in the late 1980s as a way to communicate digitally with devices that were designed to operate on 4-20 mADC current loops. In 1993, the HART Communications Foundation was established to support HART (Highway Addressable Remote Transducer) technology. The HART communications protocol is open and available to foundation members (vendors of HART-enabled devices) and the HART User Group.
HART technology is a hybrid of analog and digital communications. The technology imposes a modulated two-way digital signal on the industry-standard current loop that carries the primary process signal information. This means that HART provides two separate control signals on the same wire: the fast and robust current loop for local control and remote monitoring, and the digital signal for diagnostics, digital process information, calibration data and configuration of the operating parameters of the device. Every HART device contains 35-40 standard items of information, including device identification, calibration data, process variables (both measured and calculated, so that inferred multiple variables can be reported from a single transmitter) and a wide set of diagnostic alerts.
HART, of course, originated the DD (device description) file, which is the basis of both DDL and EDDL technology. DDL (device description language) is used to create the DD file, an electronic data sheet describing all of the capabilities of the smart field device. This permits all DD-enabled host systems to communicate with all device features of a HART-enabled device. This is now an IEC international standard.
DD is also the basis for FDT/DTM (Field Device Type/Device Type Manager) technology, which can be used to produce detailed data files for use by open asset management systems.
Because of HART’s diagnostics codes, plants with hundreds or thousands of existing HART-enabled devices can almost immediately institute asset management projects without enormous expense.
Sometime in 2006, the HART Communications Foundation will release its HART Wireless protocol. As with all HART upgrades, this one should be backward compatible to even the earliest HART devices (there are over 50 vendors manufacturing HART-enabled devices). Emerson Process Management recently released its first product based on the draft HART Wireless Protocol.
HART Wireless will provide an even easier way to release the data trapped inside your HART devices. More than a half dozen vendors have already begun designing a variety of upgrade packages to upgrade your HART transmitters to wireless. These may be as expensive as new transmitters, or as inexpensive as a “slap-on” radio transmitter that can perch on the 4-20 mADC loop. Asset management data can therefore be collected wirelessly, without even a single change to the control system. The asset management system can sit on a completely different server, and be entirely independent of the control system.
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