|
Problem:Under steady state thermal conditions (normal operating condition) the single-unit-inlet header design seemed to be an unsuitable feature for high operating of 261°F. This differential thermal load caused non-uniform thermal expansion of the unit and resulted in developing excessive secondary stresses at tube-sheet welds. at start-up the inlet temperatures were found to be ramped up at the rate of @ > 70F/hr heating rate. At start-up the inlet temperatures were found to be ramped up at the rate of @ > 70°F/hr heating rate. This Thermal shock caused excessively large thermal transient (Even greater than the normal operating of 261°F due to the much colder outlet passes) consequently leading to even greater non-uniform thermal expansion of the unit and may result in tube deformation due to relieving of developed excessive large secondary stresses. A detailed analysis established this as the cause of the existing failure (deformation of finned tubes) experienced by the Kerosene Product Air-Cooled heat exchanger .This caused gross deformation of the tube bundle causing multiple shut-downs outages in the hydrocracker operations resulting in loss of production $$$.
|
