Publications

The acid gas removal unit is designed to lower the H2S content of the fuel gas in Banyu Urip facility from 1.8% mole to 0.01% mole. To achieve the required quality, feed gas pre-treatment is required including gas cooling with AGRU inlet gas cooler (IGC). After 7 years of operation, a leak was detected in its tubes. To understand the risks posed by the leak, a risk screening was conducted, resulting in an updated working procedure. The integrity assessment also became critical to understand the leak and provide robust mitigation to prevent the same problem from happening in the future. To determine the location of the leak, inspection was completed using multi-gas detector, dye penetrant, and gas detection camera, which showed that the leak was localized only on the inlet area. A temporary clamp was installed on the top leaking tubes to prevent further dispersion, since the bottom are unable to be reached due to its narrow spacing. After looking at the data, the failure mechanism is a combination between microbiologically induced corrosion and under deposit corrosion, where natural biofilm from atmosphere and cooling water provides a place for concentrated chlorides which penetrates the steel in a pitting corrosion manner. Thus, the affirmed root cause is biofilm growth, and preventing it is vital to improve the unit’s integrity. Additionally, a process improvement study was also performed by a trial to run AGRU without cooling water to understand how to manage fuel gas production in that condition, and the result shows that the fuel gas can still be maintained, leading to proposal of future opportunities where the unit can be replaced with a cooler that has less cooling capacity and less potential integrity issue. As part of mitigation for the leak probability 0.142 per year with potential loss of $250K, a permanent jumper line installation will be installed. This initiative provide reliability benefit to minimize system failure as well as allowing bypass operation mode when maintenance and inspection are performed at the cooler. This also potentially save $1.75 M of excessive diesel consumption during leak repair by investing $170K.