Problem:The LPG gas compressors employ steam-turbines as drivers. The LPG gas compressor tripped due to high radial bearing temperature at turbine outboard side. The turbine shaft misalignment during operations was identified as the contributing factor.

Analysis: To further systematically investigate the cause of the bearing overload condition, deviation of the shafts centerline position and severe misalignment at operating condition and the seemingly improper piping support configuration, the following were completed. A detailed flexibility & stress evaluation of the inlet & exhaust piping of steam-turbine to verify if the sustained (SUS) and expansion (EXP) stresses per ASME B31.3 for the existing piping layout. This was followed by a detailed nozzle loads evaluation due to the steam piping connecting the inlet & exhaust nozzles for each of the Turbines to verify if existing nozzle loads are within the accepatble limits specified by NEMA SM-23 in the current operating condition. In addition to the above, a field assessment revealed some critical deficiencies that were observed on the inlet & exhaust piping with respect to efficient condensate removal, a detailed mechanical assessment was completed to verify the existing piping configurations.

Results Conclusion:In conclusions, the sustained (SUS) and expansion (EXP) stresses of the exisiting piping configurations (based on as-built conditions) were found to be well within the ASME B31.3 allowable limits. However, both the inlet & exhaust nozzles for each of the Turbines FAILED the required limit loads as specified by NEMA SM-23 in the current operating condition by large values. This is clearly an unacceptable condition for the continued safe and reliable operations of steam turbines. In addition to the above, some critical deficiencies were observed on the inlet & exhaust piping with respect to efficient condensate removal. These deficiencies had direct impact on prevention of condensate carryover into the steam turbines and prevention of CIWH (condensate Induced Water Hammer) in the steam piping. Given the nature of the restrictive space around the inlet and exhaust piping layout, a revised layout that provided detailed recommendations which are considered as the most optimum in reducing the current nozzle loads. It was recommended to redesign restraints and springs at select locations in addition to modifications related to steam traps and associated condensate removal piping.