Improving Existing CM Systems
Some plants may already have a conditioning monitoring system that isn't doing the job. Vectren (www.vectren.com), a power company in southwest Indiana, wanted to monitor more than 500 existing assets. Vectren's engineers were using a combination of software and spreadsheets to analyze more than 15000 equipment readings. The trend analysis software checked for problems and reported instances when assets were broken or not running efficiently. Alarms indicated problems that needed immediate attention, but the existing approach had several drawbacks.
"Dangerous conditions could evolve quickly and undetected, increasing the likelihood of costly unplanned outages," notes Isauro Martinez-Cairo, director at Invensys Operations Management (www.invensys.com) "The monitoring procedures were time-consuming, and the cause of problems couldn't always be determined immediately. Alarms were also repetitive and didn't reflect problems that a combination of conditions might have triggered."
Invensys helped Vectren achieve a better solution by implementing Avantis Condition Manager, an automated CM software solution. It tracks the performance of assets to determine exactly when maintenance should be performed, generating alerts as conditions are triggered. Staff receive warnings when conditions begin to degrade, enabling them to perform maintenance as needed, rather than as dictated by an arbitrary schedule. This reduces unplanned downtime, and enables a highly effective predictive and proactive maintenance strategy.
"The preventive maintenance functionality alone provides enough savings to pay for the entire implementation," reports Scott Brown, a reliability engineer at Vectren. "Instead of wasting an engineer's time reviewing charts, that engineer is freed to do other tasks."
Marathon Oil (www.marathon.com) had a similar problem. Marathon operates the East Brae gas platform in the North Sea, 165 miles northeast of Aberdeen, Scotland, and it had an aging vibration monitoring system that monitored and reported on the condition of the equipment. The former system was rapidly becoming obsolete, so Marathon turned to Rockwell Automation (www.rockwellautomation.com) for an upgrade.
The first phase of the work was replacing the vibration systems on the three gas export compressors, and installing Allen-Bradley XM Series intelligent I/O modules (Figure 3). These modules process, in real-time, critical parameters used to assess the health of the rotating machinery on the platform. The condition monitoring system predicts the future health of the machines, providing machinery protection where needed. Results of the upgrade included more reliable vibration monitoring and improved reliability and availability of the compressors.
We've discussed a few examples of companies replacing older CM and manual systems, and the rush may be on. As asset management and CM hardware and software become less expensive and easier to use, it pays companies to invest in the technology.
For example, in our April 2010 cover story (www.controlglobal.com/articles/2010/WorkersUnchained1004.html), we discussed how wireless technology makes it easy to add assets to a CM system and eliminates the need for operators to walk around the plant with a data logger.
Most of the major process control system vendors understand the need for CM and offer packages that work with their control systems. Or, as we saw in the Centro Energia case, their software works with other vendors' new and legacy systems as well.
Some exotic technology is available to solve tough problems. Tony Amato, president of Swantech (www.swantech.cwfc.com), Falls Church, Va., a systems integrator and supplier of CM technology, explains how one company diagnosed problems with a stress wave energy (SWE) analyzer.
"The company detected increased stress wave energy on a bottoms pump for a distillation column. The system had been in place for more than a year, and the SWE had been trending low and consistent during that time. By correlating increases in SWE to historical process data, the customer found the increases in SWE coincided with decreased and/or erratic pump flow. Further analyzing the differential pressure and the column level indicated the problem was fouling in the column packing or trays, leading to increased stress on the bottoms pump. The column was inspected and fouling was present. Following cleaning, SWE returned to normal levels," explains Amato.
Gurney of Concept Systems says companies should consider two underused technologies: statistical process control (SPC) and digital video recorders (DVRs). "SPC tools offer better data analysis and earlier, more accurate detection of problems," he explains. "Small variances, oftentimes operating within normal high/low limits, reveal equipment issues well before catastrophic failure."
As for DVRs, Gurney says they offer the ultimate troubleshooting device by giving personnel the ability to record processing lines when upset conditions or downtime are detected. "This way, plant personnel can go back and look at the video captured during these events and determine the root cause of the problem," he says.