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3. Engineering Review of Tanks & Equipment Covered by CalARP Program <br />C:\TRICH\Jobs\4515582 Leprino Tracy\Report\Leprino Tracy CalARP 040221.docx 3-11 <br />equipment. The exception to this is the ammonia tanks in the intercooler yard, and even <br />those tanks are small enough to not require full analysis of the tank walls. Most tanks <br />and process vessels are rarely filled to more than 50% of capacity. The diffusion water <br />tank is on the roof, and this would only contain ammonia if there is a release from an <br />overpressure release valve. <br />3.3.1 Failure Mode <br />Based on the detailed walkdown review, the critical failure modes of the equipment were <br />judged to be that of tank anchorage to the steel frame of the structure and to the <br />concrete foundations. Another failure mode reviewed was failure of the piping if <br />movement exceeds the bending capacity of the pipes. Pipe bracing must be adequate <br />for seismic forces, but allow for temperature changes. <br />HSC and LSC compressors: The existing support and lateral restraint appears to be <br />compliant with code requirements for the 475-year earthquake. The governing failure <br />mode of the compressors subject to seismic inertia loads exceeding code requirements <br />is the piping. In general, piping appears well supported by either unbraced or marginally <br />braced. Seismic lateral forces may damage the piping and connections. <br />Evaporative Condensers: The existing support and lateral restraint of the evaporative <br />condensers appears to be compliant with code requirements for the 475-year <br />earthquake. In general, piping appears well supported but either unbraced or marginally <br />braced. Seismic lateral forces may damage the piping and connections. <br />IB-1 Ice Builder: The existing anchorage for the main unit could not be determined. If <br />the unit has internal anchorage, support would likely be compliant with code <br />requirements for the 475-year earthquake. If not, the governing failure mode of the <br />vessel subject to excessive seismic inertia loads is failure of the piping to the well <br />anchored pumps at the west end of the unit. The flexible connections in the piping will <br />allow for significant differential movement, but excessive forces may still fail the piping <br />and release ammonia. <br />GCH-2 Ammonia Chiller (ammonia/glycol heat exchanger): The existing support skids <br />are not anchored and may slide, rock or topple when subject to seismic lateral forces <br />resulting in rupture of the ammonia piping between equipment mounted to the frame and