FROM: James D. Herberg, General Manager
Originator: Rob Thompson, Assistant General Manager
SUBJECT:
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PLANT NO. 2; REBUILD ROTATING ASSEMBLY, ALFA LAVAL CENTRIFUGE, MODEL ALDEC G3-125
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GENERAL MANAGER'S RECOMMENDATION
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RECOMMENDATION:
Approve a Sole Source Purchase Order contract to rebuild one rotating assembly for Alfa Laval Centrifuges at Plant No. 2 for a total amount not to exceed $197,846.
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BACKGROUND
Five Alfa Laval, Model ALDEC G3-125, dewatering centrifuges were installed and commissioned at Plant No. 2 by Sludge Dewatering and Odor Control at Plant No. 2, Project No. P2-92. Each sludge dewatering centrifuge employs two high-speed rotating components, a drum, and a scroll. The outside drum rotates separating the water and solids. The scroll inside the drum rotates at a slightly higher speed to push the solids down the drum to the discharge point. The components in the centrifuges are subject to very high forces and the gritty biosolids subject the machinery to plugging (which causes unbalanced rotation), erosion, and wear.
RELEVANT STANDARDS
* Safe, beneficial reuse of Biosolids
* Maintain a proactive asset management program
* Maintain a culture of improving efficiency to reduce the cost to provide the current service level or standard
PROBLEM
Centrifuge #1 was experiencing an imbalance due to suspected plugging and was also due for an internal inspection. The machine was disassembled, cleaned, and reassembled. Unfortunately, the machine was improperly reassembled. After a few weeks in operation, it was shut down under high vibration conditions. Centrifuge #1 was disassembled and the rotating assembly was found to be severely damaged.
A dispute has arisen between the Orange County Sanitation District (Sanitation District) and the Centrifuge Manufacturer, Alfa Laval. The Sanitation District's position is that the root cause of the failure was a deficient Operations and Maintenance (O&M) Manual a...
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