Big-Time Condition Monitoring

Dan Hebert is Control's senior technical editor.

Condition Monitoring Tells All

Fluor designs and builds huge process facilities such as chemical plants, refineries and power plants. Romel Bhullar, senior technical fellow/director at Fluor, says, "In almost every project we do—refineries, energy, petrochemical, biochemical, pharmaceutical or power—asset condition monitoring (CM) is an integral part."

One such project at Potomac Electric Power Co. (Pepco) involved a plant supplying power to the city of Washington, D.C. "It's critical that the power generation turbines, generators and auxiliary systems have a CM system that monitors impending failures and identifies reasons to do preventive maintenance."

Putting together such a system isn't easy. "Standard commercial off-the-shelf solutions weren't flexible and functional enough to match our needs," he says. "There were mountains of challenges: technical, people, commercial, multiple company cultures and organizations," he adds. "In these days of tough economic times, all vendors are protecting their markets and providing proprietary and expensive solutions. It makes integration very difficult."

Things are improving, but problems still exist when tying together different communication protocols. "There have been significant developments in networking technologies and communications equipment, but major issues in the bottom two layers of the OSI model still need lot of work," he notes. "Management may have different objectives than the people in operations, IT and control systems—not to mention suppliers. It's a maze out there." Bhullar says the cost to install the CM system at Potomac Power "…was several million dollars."

The data being gathered is extremely important to more than just the power company. EPRI (www.epri.org), a power industry consortium in Palo Alto, Calif., contributed to the project, so it could see the data.

"The conditioning monitoring system provides data in real time to all the EPRI stakeholders across the U.S.," Bhullar explains. "GE is looking at their new gas turbine/generator and collecting performance parameters to improve their design. Westinghouse/Mitsubishi is collecting data on their newest gas turbines/generators. Potomac Power's operations and maintenance staff are looking at impending failures. And Fluor is collecting data for validating our methods for predicting failures."

The system works, too. "The cooling system on one of the turbine blades had failed due to plugging of the passages," he says. "The system identified the problem, and Potomac was able to replace the blade in off peak hours without any loss in power."

It works for EPRI too. The information is being used by member utilities to make decisions relating to equipment selection, design configurations, maintenance and replacement policies. The data is also being used by these same utilities to validate supplier sales claims and promises of newer technologies before making the huge required capital outlays for a comprehensive CM system.

Attacking the Problem

Systems integrator Concept Systems in Albany, Ore., has implemented many high-level asset condition monitoring (CM) solutions. Michael Gurney, co-CEO, says that a CM project takes a two-level approach: First, use control hardware already in place; next, equip assets with new instrumentation and controls.

Much of the equipment in a plant already has diagnostic capabilities. "A typical automation system will control the equipment, but stop short of pulling data off the controller or motor drives. With some simple programming, a system can collect key data such as motor start/stops, cylinder cycles, fault counts, drive current, downtime, cycle time/flow rates, valve position, pressure readings and more," says Gurney.

"Collecting and correlating this data finds problems," he explains. "For example, monitoring the flow rate at known valve positions will point to issues with the valve prior to catastrophic failure. All this information can be used to make better sense of the data and better manage that asset."

Some equipment may not have the sensors needed for CM. In this case, the asset has to be equipped with sensors and tied into the control system. "The possibilities are really endless and depend on the type of asset being monitored," points out Gurney. "Because of this, a crucial step is evaluating what assets really need to be monitored and how. The question is what assets put my processing line at greatest risk. In many cases this may not be known, and that is where data gathered from existing control hardware can help."

Critical areas where a CM solution could be usefully employed include: mechanical systems for vibration and current monitoring; pneumatic systems for temperature, pressure, condensation, air flow and filter monitoring; hydraulic systems for oil pressure, temperature, level, flow, accumulator and filter monitoring; and electrical systems for power quality and temperature monitoring.

Gurney says several options exist for analyzing data. "In many cases, data can be fed directly into a computerized maintenance management software system, and the data never needs to be directly presented to maintenance personnel," he says. "Companies will also offer to take on this function for customers—where they analyze the data directly and work with the maintenance staff or with third-party mechanical, pneumatic, hydraulic or electrical specialists."

The other critical element of a CM solution is measuring the results. "Overall equipment effectiveness determines gains recognized by a CM solution," he explains. "Having this data prior to the CM implementation will deliver quantifiable data on the improvements when viewed before and after the project."

Powerful Condition Monitoring

The installation at Centro Energia Teverola's 150-MW combined cycle cogeneration power plant in Teverola, Italy, near Naples, illustrates two key aspects of modern condition monitoring (CM) and asset management systems.

First, it may not matter what kind of new or legacy control system is installed at your plant because modern CM software packages can work with almost any system. Second, you don't have to develop specific knowledge about CM because outside services exist that will analyze the data and recommend best courses of action.

Centro Energia had a legacy Bailey Infi-90 control system with 5000 I/O, and it wanted to monitor clogging problems with inlet filters on its gas turbines as well as other operations. The data Centro Energia needed to analyze was already being collected by the control system, so all the company had to do was install Emerson Process Management's AMS Performance Monitor software and contract for Emerson's remote analysis services.

It's necessary to monitor the gradual deterioration in filter performance and calculate the cost of the resulting reduction in turbine performance. By comparing this with the cost of the maintenance required, the most appropriate point to replace the blocked filter can be determined.

But Centro Energia doesn't make the determination: Filter and other data from Teverola is transmitted to Emerson's performance monitoring center of expertise in Teesside, in northeastern England, where experienced engineers analyze the data and produce reports showing performance. These reports can be accessed via any standard web browser, and are based on thermodynamic models developed for each machine.

In addition to the online information, Emerson also provides advice about the operational efficiency of machinery. Existing or potential problems are highlighted, as well as new opportunities to improve overall efficiency.

Vincenzo Piscitelli, general manager, Centro Energia Teverola, says, "We can assess the effectiveness and economic return of our maintenance activities, which allows us to determine what maintenance work is required to improve equipment performance."

This improved planning has also enabled Centro Energia Teverola to reduce average repair times from seven hours to two hours.