Lesson Learned Statement:Acceptance tests for installation of new equipment should include full loop tests for instruments with a potential for sensing line errors. Similar care should be exercised following system modifications or major repairs having a potential to affect sensing line configuration.
Discussion:In approximately 1980, project V677 upgraded the ventilation system for the 340 Waste Handling Facility. Modifications included upgrading the K1 stack HEPA filter differential pressure (dP) monitoring equipment. The project specifications did not include detailed drawings for routing the sensing lines. During field routing of the twelve, 1/2 inch stainless steel tubing runs, "cornering" techniques were used that inverted the expected positions of the lines relative to the cabinet bulkhead. As a result, the sensing lines for one side of the dP gauges for two sets of filters were reversed causing the differential pressure across them to be monitored incorrectly.
During ventilation adjustments associated with a recent HEPA filter replacement, dP anomalies were observed and the misrouting problem was identified. The configuration deficiency was corrected by rerouting the flexible tubing inside the gauge cabinet.
Analysis:Full system installation verification should have been performed in 1980 before the system was placed in operation. Acceptance testing of the newly installed piping and equipment did not fully test the entire dP measurement system with a full-loop check. As a result, the incorrect piping configuration was not identified. Field walk down and efforts to develop as-built drawings in later years did not include detailed verification of the sensing line configuration because of their location in a high radiation field. During normal system operation, the three filter banks were in parallel, so filter dP readings did not display significant anomalies. Because the HEPA filters are changed as a group and operated in parallel, the misrouted piping configuration was not identified by differing pressure readings on the gauges.
This gauge anomaly did not result in any increased risk for radioactive release. While mismatched, the overall filter dPs were still being effectively monitored.
This event demonstrates a need for improved attention to detail during installation of piping systems and development of acceptance test criteria to validate that installation. The Acceptance Test Procedure performed in 1980 introduced a pressure signal to each of the gauges at the low dP port of the gauge rather than at the duct where the signal originates as would have been the case in a full-loop check.
Recommended Actions:Ensure that instrument installations and modifications are thoroughly checked during acceptance testing by introducing test signals at the point of origin.
Originator:Fluor Hanford, Inc. Submitted by Don McBride; (509) 373-5698
Contact:Project Hanford Lessons Learned Coordinator; (509) 373-7664; FAX 376-6112
Name Of Authorized Derivative Classifier:Not required
Name Of Reviewing Official:John Bickford
Priority Descriptor:Blue / Information
Keywords:instrument, differential pressure, loop check, field routing
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DOE Function / Work Categories:Conduct of Operations - Configuration Management
Inspection & Testing
Maintenance - HVAC
ISM Category:Perform Work
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