Reliability Optimization of Compressed Air Systems in Nickel Smelter Industry based on Decision Making

The air plant is one of the important systems in the production process in the nickel smelter industry. The air plant consists of several compressors, distribution pipes, air sector systems, air dryers, separator tanks, and reservoirs. There are 13 centrifugal compressor units in the air plant which work with a total capacity of 49,000 CFM, while the demand is 35,000 CFM. The reliability of each compressor greatly influences the performance of the air plant, therefore it is necessary to determine the optimal number of compressors that can work on the air plant. The optimal number of compressors will result in higher energy efficiency so that production costs can be reduced. The purpose of this research is to produce maximum system reliability by determining the optimal number of compressors with a minimum air supply of 35,000 CFM. This research began with collecting maintenance data and piping and instrument diagrams, processing maintenance data, and creating an optimization model. There are three schemes as model variations used to obtain optimization values, when all compressors can work, when all compressors in section A3 are on standby, and when each section has one compressor on standby. The best scheme is shown when the system works with each section having one compressor on standby. This scheme has a system reliability of 0.655 when t is 4000 hours.