Big Data Pays Big
No matter the end product, process economies are critical to stay competitive, and, therefore, so is attaining cost-effective plant maintenance. Condition monitoring (CM) plays a vital role in predictive maintenance by allowing a producer to actively prevent breakdowns and optimize production processes.
CM is typically seen as a specific equipment-based predictive maintenance tool—vibrations analysis of a boiler fan motor, for example—but there is also operations-based CM, which can be used to determine the overall health of the system. “We monitor individual components of the plant, and then we look at many of them together to monitor the entire process of the plant, to see trends in the plant and what’s happening with the overall machine,” says Kendric Wait, a representative of biomass power generation company Eagle Valley Clean Energy.
Power producers invest in ways to identify and eliminate potential reliability issues throughout a plant’s operations—from the initial delivery of raw material to the renewable power sent to the grid.
“Anywhere you don’t have redundancy of a single supply line in the process is a critical point,” Wait says. Eagle Valley’s 11.5-MW plant in Gypsum, Colorado, has a few redundant systems, but the bulk of the plant is a single supply line. Any single component that fails could easily interrupt the entire process and whether it’s a $5,000 gearbox or a very expensive turbine, it’s all critical to the process, Wait emphasizes.
Although producers acknowledge best practices haven’t necessarily been established, biomass power plants throughout North America are taking similar approaches when it comes to predictive maintenance. No matter the age, size or sophistication of a plant, there are key process components every producer should monitor to some degree.
Basic human senses compliment technology-based data acquisition efforts. Biomass plants, such as Eagle Valley, utilize plant staff as one way of monitoring, with regular walkthroughs of the plant—looking, hearing, smelling, striving to identify any problems that may arise. It’s the interaction between humans and machines through user interface technology where biomass plant processes are recorded and stored. Software packages developed for CM purposes can be individualized to track and trend what’s desired, and there are a number of platforms available for users to understand, diagnose and control process conditions in real time. Usually, producers follow a combination of engineering guidelines, OEM recommendations and what works best based on experience when it comes to predictive maintenance.
A computerized distributed control system is used at the power plant serving the University of Iowa. The plant also uses a data historian called PI that stores historical operating data. “This is very useful for event root cause analysis, troubleshooting and operations monitoring,” says Ben Anderson, power plant manager.
Atlantic Power Corp.’s biomass power plants deploy a real-time enterprise data historian called eDNA, which collects, archives, displays, analyzes and reports on continuously streaming time-series data. “We can develop tools within eDNA to help monitor plant efficiencies and optimize various parameters, so that we know what our optimal performance is, and then we adjust our operation to meet that,” says Sean Gillespie, general manager with Atlantic Power. “We monitor both short-term and long-term trends to evaluate the impact of our changes on plant output and emissions, and are constantly fine-tuning operations to meet production and environmental targets with the least amount of wood burnt possible.”
Atlantic Power owns four biomass power plants—two in the U.S., and two in Canada. The past three years, Gillespie says, all the biomass plant managers and some of their teams have gathered with key support staff and members of engineering, environmental, and health and safety teams at a biomass summit. “We’ll have two- to three-day meetings where we’ll share best practices between sites, share challenges, identify opportunities, and look for guidance from our peers on what we can do to address problems and optimize plant performance,” Gillespie says. “We also make sure that we do a review and reconciliation of our preventative maintenance plans, so that we’re not doing too much maintenance at any one site, but we’re making sure all the required maintenance is done consistently between assets and in compliance with all required regulatory requirements.”
Another biomass power producer with years of operational experience is Minnesota-based Great River Energy’s Elk River Energy Recovery Station. This retrofitted waste-to-energy plant converts up to 1,050 tons of refuse-derived fuel per day into as much as 30 MW of energy. The plant deploys Emerson’s 1500DST DeltaV system to monitor and control the plant, consisting of three boilers, three turbines, fuel handling and baghouse. Mark Holt, senior engineer, says a bulk of the monitoring they do is tied into that system. As an engineering and technology company, Emerson offers a number of equipment condition monitoring including online vibration monitoring, motor diagnostics, infrared thermography, laser alignment and balancing and oil analysis.
Eagle Valley’s biomass plant in Colorado is fairly new, commissioned in 2012, and just recently restarted operations in February, due to a fire that put the plant out of commission in late 2014. In this day and age, Wait says, when smaller plants are built under full EPC contracts, it makes sense to rely upon the engineering staff’s monitoring recommendations. The primary system deployed at Wait’s plant was developed by Wellons. “Equipment might be slightly newer, different than your operational staff’s experience,” Wait adds. “I think in a new plant today, the monitoring systems typically outpace the experience of the operating personnel.”
Track and Trend
Since CM is based on trending, it requires that baseline conditions be defined so there is a reference point for comparing and interpreting the obtained data. Overall, plant processes should stay within a standard deviation, and if a change occurs in the trend, it should be linked to some process or mechanical variable. “Almost all of the parameters that are monitored electronically have some sort of expected range of operation, and if the parameter goes outside of that range, the computer system will signal an alarm,” Wait says. He shares that his staff takes the time to understand why there was an alarm, what the parameter values are, and then troubleshoots the issue.
Holt adds that, in addition to alarms, certain components are designed to shut down or trip to prevent further damage to the equipment if something goes awry. According to Holt, plant monitoring is all about creating a better user interface to understand what the alarms and numbers mean, so it can be easily interpreted and used to make improvements.
According to Justin Price, principal with Evergreen Engineering, the real trick is knowing what to measure, how it’s trended and how you’re going to use that data. “If you’re measuring the wrong thing, then you might be going after the wrong key performance indicators (KPIs),” he says.
The staff running UI’s power plant measure several KPIs associated with safety, maintenance costs, operational efficiencies, the percentage of renewable energy and more. One example is boiler efficiency monitoring. “We look for any significant changes based on a simple calculation of total fuel into the boiler (measured from a mix of meters in the plant) and steam out of the boiler (measured with steam flow meters),” Anderson says. “This gives us a baseline, and can help identify if a fuel has lower-than-expected Btu per pound, or if there are other issues within the boiler. This is especially useful for fuel transitions, say from woodchips to energy pellets.”
Around 15 to 20 percent of biomass materials, including oat hulls, woodchips and pelletized miscanthus, are cofired with coal at the plant. The UI staff calculates the percentage of renewable energy generated by monitoring the total amount of million Btu from renewable sources and comparing that to the campus’s total energy usage (including purchased power). This percentage and why it’s higher or lower, as well as operating plans, are communicated at morning kickoff meetings, Anderson shares. Variations could be attributed to a number of factors—like truck unload issues, plugged systems, etc., he says, but the ultimate goal is to understand how the operating plan affects the percentage of renewable generation, and have everyone aware that their actions can help with achieving the targets.
Most biomass plants collect fuel from a variety of suppliers. Since UI introduces a few different types of biomass into its plant, the added variability leaves opportunity for issues to arise. “I think the power plant has done a nice job of more closely monitoring our systems, as we’re changing out fuels or increasing fuels, so we have enough data to go back and say introducing this fuel at this percentage might have caused this issue in the handling system or might have caused this spike in NOx emissions,” says Ingrid Anderson, UI environmental compliance specialist.
Gillespie recalls the wet spring in Georgia around Atlantic Power’s Piedmont plant—when wet, biomass fuel can wreak havoc on efficiencies. “It’s important to carefully monitor moisture content to the fuel coming in, and then you adjust your operating parameters to mitigate the risk of NOx exceedances or poor performance,” he says. “Moisture content is evaluated once or more per shift, and then we have fuel managers at all of our sites whose job it is to go out and procure the best quality fuel possible.”
Eagle Valley is the only utility-scale biomass power plant in the state of Colorado, so the facility developed its own biomass fuel market. “You get what’s available, or what suppliers are offering—whether it’s a certain species or certain kind of beetle-kill wood,” Wait says. Fuel is secured from a dozen different locations for the plant, and the staff also monitors the fuel yard multiple times a day, both through computer monitoring and visual inspections.
Monitoring air emissions is also important at biomass power plants. UI just received a plantwide applicability limit (PAL) permit, which establishes a facility-wide cap on emissions for several different pollutants across campus. Ingrid says this gives them a lot of flexibility operationally, but the tradeoff is they do more emissions monitoring by keeping track of monthly data on all sources to comply with the permit.
The Elk River Energy Recovery Station has monitors installed on the high-speed AVP Anhydro rotary atomizers in the exhaust gas scrubbers, which are commonly used in power plant scrubbers to reduce airborne pollutants before they reach the baghouse. Emerson worked with the plant to implement what’s called the CSI 9420 Machinery Health Transmitter for predictive monitoring of these atomizers. Various parameters are measured on the instruments mounted on the atomizers at the energy recovery station, including overall vibration velocity, maximum waveform and speed.
CM programs for a biomass plant’s rotating equipment can include those supplied by the vendor. For example, Eagle Valley’s turbine condition monitoring system from Siemens, as part of its purchase order, monitors performance and around 50 to 60 operational parameters on the turbine itself, according to Wait. “We monitor those constantly and record trends daily to have a daily snapshot on turbine performance,” he says. “The plant operator who’s on shift is monitoring and Siemens is monitoring, and then Siemens will come in on a regular basis and evaluate various components in the plant and on the turbine itself and give us a recommendation.” According to Wait, Siemens suggests if they’re doing real-time monitoring and maintenance of the equipment, turbine equipment life on its major rebuild interval can extend to double what it would be if not monitoring. “I think that’s a good indication that your maintenance costs can be roughly cut in half with in-depth monitoring,” Wait says.
UI uses GE’s Bently Nevada vibration monitoring system on its turbine generators, vibration analysis and oil analysis on rotating equipment, and thermography on electrical equipment.
Automation has become the industry standard for modern plants. According to Wait, Eagle Valley paid for an automated plant, but unfortunately didn’t get automation in a number of areas their contract requires. The company expected and needs automation because it only employs 13 people. “We don’t have the plant staff to walk around and see things and measure temperatures locally, as you might have in an old plant that may not have those automated monitoring systems,” Wait says.
Aging plants make upgrades when possible. “We just installed a new continuous emissions monitoring system for our environmental emissions,” Ingrid Anderson says of UI’s power plant. “There are still some systems we use that are less automated, so the plant has been looking at what opportunities there are for upgrading.”
Minnesota’s Elk River Energy Recovery Station was retrofitted in 1989, but the power plant began commercial operation with coal and oil dating back to 1950. Over the years, they’ve updated much of the instrumentation for monitoring. Holt says at the plant they conduct mostly in-house condition monitoring, but in some cases, such as for vibration monitoring for their fans and turbines, they have third-party contractors who come in on a periodic basis and do a vibration route.
Virtually, every component and process at a biomass power facility can be monitored to some degree, but the key is what will help a producer meet targets and improve the plant’s bottom line. Whether being used as an equipment-specific predictive maintenance tool, or, generally, to improve a plant’s overall operations, CM can save a biomass power producer time and money by circumventing unscheduled downtime.
UI power plant staff has used fan vibrations data and bearing temperatures to determine if and when repairs would be needed to rotating equipment. “This specifically has saved us a few times on the secondary air fan motor for the circulating fluidized-bed boiler,” Ben Anderson says. “We were able to shut down prior to a catastrophic failure.”
At Great River Energy’s WTE facility, Holt adds, “The condition monitoring we do to monitor the fuel conveyer system gives us the ability to shut down the system before a failure happens.”
Author: Katie Fletcher
Associate Editor, Biomass Magazine