Coal, O&M

Remote condition monitoring saves personnel time,maintenance expense

Issue 1 and Volume 99.

Remote condition monitoring saves personnel time,maintenance expense

Remote condition monitoring has saved more than $650,000 in downtime, personnel time and materials during the first 18 months of operation for Lone Star Energy Corp.`s Encogen Four power plant in Buffalo, N.Y. Cost to the plant for hardware, fees and training associated with the monitoring system was $35,000.

Encogen Four is a 62-MW plant capable of producing 543,000 MWhr of electricity annually. The plant began commercial operation in May 1992 and has four major pieces of equipment: two gas compressors, a steam turbine and a base-loaded GE Frame 6 gas turbine with dry low NOx combustors. Electricity from the plant is primarily sold to Niagara Mohawk Power Corp., which uses it to power residential Buffalo.

From the beginning, the management team at Encogen Four was determined that condition monitoring activities be controlled by established experts, rather than attempting to develop capabilities in-house. The plant contracted with StarLink Remote Analysis Services from SKF Condition Monitoring to do the job.

“Encogen Four has a 98 percent on-line production rate and a stretch of more than 3,800 hours at full load without a curtailment,” said Charles Stodolka, plant manager. He said the StarLink installation is “paying off handsomely.”

The program consists of sensors, software, a data collection instrument, a PC and a modem. Technicians establish data collection routes, analyze data and diagnose machinery problems. StarLink provides training and is on call to assist in prevention of downtime and reduction of maintenance costs.

The system collects data from more than 800 points, with 750 monitored by a data collection instrument equipped with a portable magnetic vibration sensor. The 50 fixed sensors monitor positions that are not accessible by hand, transmitting data to the facility`s control room. Collected data is downloaded to the PC and sent by modem to the StarLink service headquarters, where the data are analyzed. If there is a dramatic increase in amplitude on any point monitored, more measurements are taken to verify the problem and determine a course of action.

Stodolka has seen dramatic benefits from the establishment of baseline vibration signatures. Encogen Four has system standards to measure new signatures against, allowing technicians to identify, document and prevent several potential problems that would have caused downtime.

One problem dealt with excessive vibration in vertical waste recirculation pumps. Analysis of vibration data helped identify an improperly seated bearing. In correcting the bearing problem, technicians discovered that the wrong grout was used to build the base holding the 4-ton pumps. Correcting that problem required moving the pumps, regrouting and machining the pump faces. The $11,000 maintenance cost was covered by the installer`s warranty.

“Pump failure due to the grouting problem would have meant returning the pumps to the manufacturer for repairs for two weeks,” Stodolka said. “And we would have lost about $500,000 in revenues during the first year. Even though the equipment was brand new, it would have experienced catastrophic failure within a year, and pump replacement would have cost an additional $80,000.”

A primary function of the monitoring system is trending equipment to prioritize repair work and determine whether equipment can wait until a planned downtime for repairs.

In one case, a coupling in an exhaust blower needed repairs. If unrepaired, the coupling could have caused a major trip, costing the plant an estimated $72,000 in downtime and replacement costs. Immediate replacement would also have incurred downtime. By continuously monitoring the coupling and assembling all parts for replacement, repairs were held until a planned half-hour maintenance window.