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A finding of very low safety significance with an associated non-cited violation of Technical Specification 5.4.1.a was self-revealed when plant operators discovered a pencil-thick lube oil leak coming from a flexible coupling on emergency diesel generator 12 during planned surveillance testing. Specifically, a lube oil leak developed when the flexible coupling located between the engine driven lube oil pump and the lube oil filter failed due to improper torque applied to the coupling On April 20, 2018, the licensee was performing a routine slow start surveillance of emergency diesel generator 12 (EDG12), when plant operators noted a pencil-thick lube oil leak from the flexible coupling fastener located between the engine driven lube oil pump and the lube oil filter with the engine running in idle. Plant operators subsequently shut down the engine, discontinued the surveillance, and EDG12 was declared inoperable. The licensee performed an investigation and found the flexible coupling fastener was torqued to 120 in/lbs. Maintenance procedure 35.307.008, Emergency Diesel Generator Engine General Maintenance, Enclosure X, Revision 44 required a torque value of 240260 in/lbs for the size of piping the fastener was on. The coupling was last disturbed in 2011, and the maintenance procedure at that time did not contain information regarding torque values for flexible couplings. A similar flexible coupling fastener failed in 2016 due to inadequate work instructions for torqueing flexible couplings (NCV 05000341/201600401, ADAMS Accession Number ML17030A328), and corrective actions were developed to use the vendor recommended values that had already been added to the maintenance procedure as Enclosure X in 2014. However, the corrective actions did not require all flexible couplings to be checked to ensure they were appropriately torqued. Opportunities existed for the licensee to ensure these flexible couplings were properly torqued according to vendor recommendations, either through scheduled maintenance online or during refueling and forced outages. Therefore, on April 20, 2018, another flexible coupling that was not checked as an extent of condition failed due to an under torqued condition.
|Report||IR 05000341/2018003 Section 1R12|
|Date counted||Sep 30, 2018 (2018Q3)|
|Inspection Procedure:||IP 71111.12|
|Inspectors (proximate)||T Briley|
|Violation of:||Technical Specification|
Finding List (Fermi) @ 2018Q3