CS07: Dry Screw Compressor Trip on Axial Displacement during Cold Start

Abstract

Dry Screw Compressor experienced HH axial displacement trip within 15 minutes after every cold start-upsince the MMS system upgrade in 2016• Failed attempt to successfully restart this compressor after every planned maintenance activity has causeddisruption to Operations Process planning• Trip recurrence data indicated rotor thermal growth beyond trip limits Once the compressor trips, the axialprobe position needs to be adjusted to allow a successful re-start of the compressor• Further analysis of rotor thermal growth ascertained that during the first few minutes the effect of rotorthermal expansion was more dominant than that of the gearbox casing, which only occurred about twohours later• Correlation between the trip recurrence and the compressor thrust bearing type (fixed pad) was alsoevaluated as part of the investigation• Wear allowance of the thrust bearing and the rotor to casing clearance were evaluated in order to determinethe trip effects to the overall train integrity• Reevaluation of the protection mechanism of the machine was done and changes made to remove the tripon axial• This case study presents details of the problems, background and the engineering assessment to achieveviable and fit-for-purpose solution