The objective of this study is to estimate the fatigue life of inlet separator at operating conditions and to check the equivalent Von- Misses stresses at designed conditions.
3D modeling has been done as per available drawings. Thicknesses for shell and saddles have been considered as given in drawings. A uniform thickness of 22.5mm has been considered for cylindrical shell as well as dished heads.
With the help of Finite Element Analysis study, actual stress distributions in different components of inlet separator and the actual behavior of separator at operating and design conditions have been determined. During operational service, inlet separator will be subjected to cyclic or repeated stresses.
Maximum Von-Mises stresses for occasional wind and seismic scenario are under yield strength of the material.
For operating pressure and temperature loading, minimum requirement for vessel Life is 7000 Cycles to operate safely for 25 years. Minimum number of cycles required for full operation span is 12600 cycles. Nozzle N1 has been analyzed for slug loads where frequency is considered 20 times per hour. At the selected frequency of loading, assuming complete reversal in opposite direction of load, the fatigue life is calculated 2 years. However, we assume that at such high frequency of slug loading, it is safe to consider only 50 % reversal in load due to damping from liquid. With this consideration, the fatigue life of the nozzle N1 is 16 years. Therefore, a change of nozzle neck pipe with increased thickness is recommended.
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