Air Compressor Site Performance Testing: Apparent Simplicity & Practical Complexity
Air Compressor Site Performance Testing: Apparent Simplicity and Practical Complexity: The performance of a steam turbine driven air compressor deteriorated by 35% over a span of four months. This Case Study elaborates on the identification, analysis and restoration of performance. Compressor Rating: Casings: 2 with intercooler. Capacity: 19,497 Inlet m3/hr [11,476 ICFM]. Speed: 8400 rpm. Rated mass flow: 21,585 Kg/hr [793 lb/min]. Power: 2.3 MW. Discharge pressure: 10.6 bara. [152.3Psia]. The subject air compressor forms part of the utility and instrumentation air supply system to an oil refinery. Constant pressure at header that supplies air to instrumentation system is very important. Any reduction in mass flow of dry air to the air supply system will result in reduction of the header pressure. Drop in air header pressure was experienced that prompted potential deterioration in air compressor performance.Performance testing at site indicated operating points almost on the design surge curve. The difference between the design polytrophic efficiency and the polytrophic efficiency calculated from data collected during operation at comparable operating points for the first and second casings were marginal, 0.3 to 0.7 percent. The calibration of the instrumentation used during testing was verified and the air inlet filter elements were replaced. After examining other possible causes the compressor was opened and it was found to be clean. The root-cause was found to be an unexpected obstruction.The Case Study shows how important it is to measure the inlet conditions as close to the compressor inlet nozzle as possible besides emphasizing on thorough compressor system analysis.
Ganesan, S.T. (2004). Air Compressor Site Performance Testing: Apparent Simplicity & Practical Complexity. Texas A&M University. Turbomachinery Laboratories. Available electronically from