[1F2] Condition monitoring and failure analysis of a liquefied natural gas plant cryogenic heavies removal column reflux pump
E Pereira
Glasgow Caledonian University, UK
Critical machines such as pumps are subject to wear and ageing. The materials and components they are made from degrade over time and, if no action is taken, they will eventually fail. Fortunately, most types of failure can be prevented by maintenance. To plan maintenance effectively, the plant operator must have accurate information on which components need repairing or replacing and when. Maintenance planning management plays a big role in preserving equipment reliability and the availability of a liquefied natural gas (LNG) plant. This paper investigates failures in a cryogenic heavies removal column reflux pump on an LNG plant. Root cause analysis (RCA) was conducted to determine the pump failure pattern. Failure of the thrust equalising mechanism (TEM) caused excessive downward thrust in the rotor, as demonstrated by the gap seen between the alignment of the wear ring and the casing on the seized impeller. Debris (aluminium, stainless steel and iron) from the pump obstructed the flow to the ball bearing and caused a lack of lubrication and cooling for the bearing, which consequently increased the bearing temperature and created localised heat vaporisation, and the bearing catastrophically failed. The pump casing was found with damage from the impeller thrusting against it during its failure, with deposits from the wear ring embedded in the contacted area. This would have placed the bearing into axial strain and caused the failure. Condition monitoring graphs of the pump performance prior to failure are critically analysed and presented in this paper.
