An LNG Plant or any Petrochemical Plant was constructed on the basis of discovered feed gas with full scale capacity. As the feed gas has decreased, the plant capacity is required to be put in idle or mothball mode. In that period, the plant facilities have to be preserved and inspected to maintain the integrity. The static and rotating equipment, electrical equipment, and instrumentations need to be maintained. The focus in this paper is how to preserve the rotating equipment. Since they always have clearances between rotating part and stationary part, nitrogen containment only is not always adequate to preserve the internal parts.
Failure Mode Effect and Criticality Analysis (FMECA) is one of the tools to define how to preserve rotating equipment. The analysis considers the following essential factors: duration of idle period, equipment functions, equipment mode of failures, preservation method, test convenience, cost of consequence, and safety.
This paper takes the case of FMECA of one of the LNG Process Train in Badak LNG that has undergone idle period. Rotating equipment consists of Steam Turbines, Centrifugal Gas Compressors, LNG Pumps, Hydrocarbon Pumps, High Speed Pumps, Lube Oil Pumps, and Fin Fans. The evaluation is down to its auxiliary parts such as Mechanical Seal, Bearing, and Hydraulic Governors.
The FMECA study also defines criticality of equipment in the frame of future as the idle period has ended. Rotating equipment may have issues on corrosion and performance. One possibility is whether the equipment or its internal parts (such as rotors, diaphragms, etc) need to be removed from site to storage or warehouse.
The criticality also considers the mode of operation of the equipment and their fluid services. This case study presents evaluation of following fluid services: High Pressure Steam, Medium Pressure Steam, Low Pressure Steam, Lubricating Oil, Amine, Natural Gas, Liquefied Petroleum Gas (LPG), and Liquefied Natural Gas (LNG).
As the result of FMECA study, the facility has to be preserved in specific methods and measures based on the period of idle. The method provides recommendation of preservation treatment, storage specification, testing requirement, product lifecycle study. The methods and measures performed during idle period are expected to maintain the facility integrity when it needs to be in operation again.