Ingenuity Magazine Summer 2021

1 2 3 When the team observed two continuous insulation cracks around the base of the tower, the insulation around the tank was removed to allow visual inspection of the shell. No cracking of the fiberglass shell was observed. Several concepts were considered for bracing, including: 1) bracing inside the building, 2) guy wires, and 3) bracing to a pipe bridge Attachment to the bridge was determined to be the most viable option for bracing. After evaluating readily available steel materials, the bracing was designed as an emergency shoring measure and material procurement began. Bracing inside the building – This would require removing roofing and attaching steel members to the top of CMU walls. The construction of the CMU walls, unknown given the age of the building, was assumed to be unreinforced. Pond determined the risk for this option and the significant amount of work required made this option non-viable. Guy wires – Guy wires would be placed at three locations around the tower. In evaluating the surrounding structures, Pond could not find three viable anchorage points. In addition, guy wire tension must be adjusted equally for each wire, to avoid pulling the tower in one direction. The investigation team found that the 8-inch reactor inlet from the tower had been updated with a new expansion joint. The newly installed joint may have failed or did not function properly during a recent surge, thermal growth, or seismic event, causing stress on the tower’s 8-inch outlet penetration. The team also observed that the expansion joint was installed on the tower side rather than the reactor side as specified in the drawings. Finding cracking had only occurred and propagated in the outer fiberglass jacket and insulation, the team determined the scrubber was suitable for continued service. Bracing to a pipe bridge – A newly constructed pipe bridge exists directly adjacent to the tower. Using as-built drawings, Pond built a full analytical model of the structure while on-site and determined the bridge was adequate to carry the bracing and wind loads. This solution reduced loads at the base of the tower, mitigating risk of a collapse. Reactor Piping bridge Expansion joint After the temporary band secured the tower, the hazmat team drained the tank and declared the pit area safe for qualified and authorized personnel to access the space. During the process investigations, it was determined that the expansion joint on the scrubber discharge line to the reactor was replaced recently. It is possible that the new expansion joint was not properly installed and consequently the system could not properly absorb thermal stresses. Likewise, the piping could have been moved, creating a moment load that initiated the fracturing. It was also noted that the expansion joint was on the reactor nozzle and not the scrubber where it should be located. Having the expansion joint at the scrubber nozzle is designed to prevent damage from piping vibrations. Expansion joint Bulge along side of vessel Main system pump Scrubber tower Scrubber tower Pond Ingenuity | Summer 2021 11