Thursday, January 5, 2012

Patience is a Virtue When Searching for Inleakage Failures

A power plant in Texas with an 830 megawatt turbine / condenser tried various methods and other vendors to identify the source of condenser inleakage that was contributing to >30 scfm of off-gas flow and 3.27” Hg of unit back pressure.  All these attempts failed to pinpoint the root cause of the issue, so in October 2011, American Efficiency Services was called upon for help.

Within the first six hours, AES identified the root cause of high off-gas and back pressure as the 6A Low Pressure Heater, Normal Vent Valve Line.  The line was deteriorated at a weld that was allowing the air into the steam space.

After temporary repairs were made to the leaking area by placing a combination of duct tape and RTV sealant over the breech, the condenser off-gas decreased from >30 scfm to 8 scfm.  There was still leakage recorded through and around the temporary patch during the retests.  Permanent repairs to the vent line were scheduled for the upcoming outage.  There were still nine additional leaks that were not addressed while the inspection crew was on-site.  Condenser off-gas is expected to decrease to <3 scfm after permanent repairs.  That is equivalent to 0.36 scfm per 100 megawatts, well below the industry standard of 1 scfm per 100 megawatts. Finally, the customer had an answer and a plan thanks to the AES crew and their findings.

Indeed, during our years of conducting inspections, we’ve learned that you must be patient and not assume a component is operating under a positive pressure.  It was determined by plant personal that this area was previously overlooked because it was assumed to be operating under a positive pressure.  AES always thoroughly inspects all areas to ensure all leaks are identified during a condenser air inleakage inspection.

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