Vol.13, No1, 2013, pp.17–22
UDC 620.19:621.65

Valves (formed from ball and seat) in pistons pumps ensure the movement of the petroleum from the deposit to the surface. The balls must withstand the complex erosive-abrasive wear determined by corrosive environments, while having a resistance to the micro cutting and micro fatigue as much as possible. In the case of extraction through underground combustion, the effect of high temperature will also occur. Several experimental batches of balls with structural gradients are made using different extremely hard alloys. An analysis, using finite elements, of the tension states that occur during the process is performed and the life span of the balls is estimated. We present the analysis of the ways of deterioration caused not only by usage in the process, but also by the manufacturing defects of balls with a structural gradient. The complex analyses that are performed to determine the causes and the mechanisms of deterioration are presented and also technological ways to improve the life span have been proposed.

Keywords: oil extracting pump, valves, balls, wear, extremely hard alloys, stresses, fracture, fatigue, FEM, CAD, life span