Determination of the mechanical power losses of engine-compressor GMVH for diagnostic purposes

The engine-compressors GMVH types are used in the national gas transmission system in Poland. There is a danger of scuffing of the working components of the engine-compressor particular pistons and cylinders during the process of their exploitation. The growth of resistance in motion parts of the machine is the main symptom of the scuffing. In the cinematic system of the engine-compressor where the engine and compressor are fully mechanically integrated it is impossible to assess the power of mechanical friction without stopping the machine. But if the engine-compressor is equipped with a cylinder pressure measuring system it is possible to determine the indicated power of all compressor and engine cylinders and assess the friction losses as a difference between the sum of the engine 's cylinder s indicated power and the sum of the compressor's cylinders indicated power. In the differential measurements of absolute values measuring errors are accumulated so considerable uncertainty of the measured parameter is expected. The accuracy of the friction power losses assessment method is not sufficient for research purposes. However, despite the expected significant errors, assessed parameters trends observation should allow to detect ofrapid changes of machine technical condition caused by piton scuffing. To ensure the sense of this method a precise measurements and in particular the error consistency of indicated pressure assessment of all cylinders in long time period are necessary. The experience from engine-compressors monitoring and diagnostic system services, the main sources of errors and methods for their minimization are described in the paper.