Compressor package: Failure analysis & Reliability enhancement

Instrument Air (IA) compression system is a critical utility system that is responsible to deliver filtered and dry air to various process stations within the plant. The compressed air is used to manipulate valves that are crucial for plant control and emergency shutdown systems. Inadequate operation of the IA compression package leads to reduced system availability, which introduces safety hazard and leads to serious operational interruption. This paper analyzes a case study of frequent system tripping due to hot air recirculation phenomenon (HAR), using actual field measurements and computational fluid dynamics (CFD) simulations, to propose solutions for maximized system reliability. This research work presents a case study of HAR at oil and gas offshore plant that reduced the performance of an air-cooled IA compression package. This in turn caused the system to experience repeated and frequent trips due to increased temperature within the package. Therefore, the need for exhaust hot air dispersion analysis of discharged air from air-cooled heat exchangers is becoming of great importance. A detailed three-dimensional CFD model, that represents different installation arrangements of the compressor unit area, was built to simulate the HAR and its influence on the overall performance of the compressor unit. Actual site measurements were collected, analyzed and compared to CFD predictions. The effect of wind speed and direction with relative to the compressor package installation location on the platform was analyzed and discussed. Recommendations and mitigation measures to avoid frequent system outings and exhaust HAR are provided based on CFD outcomes. The results of the analysis showed that HAR was the main reason of the frequent system tripping which is directly associated with the installation location of the compressor package. The CFD predictions calculated the flow and temperature distribution in the compressor area, and results were compared with actual site measurements, taking the site weather conditions, wind speed and direction into account. Excellent agreement between CFD results and field measurements was observed. In order to prevent system breakoffs from happening, a short-term mitigation of installing a ventilation blower inside the package while introducing additional suction louvers in the enclosure was made to enhance heat transfer. Moreover, a long-term solution to install exhaust ducting to route the exhaust hot air away from the air-cooler intake of the compression package is proposed. Both mitigation measures were implemented and the frequent tripping was eliminated. The influence of HAR on air-cooled compression packages is not well recognized in oil and gas industry. This study utilizes in-depth engineering analysis techniques to enhance the air compression system reliability using advanced engineering simulations.