The Influence of Seat Fatigue Test on the Leakage in Ball Valve

The ball valves are used in places of pipelines where turn on/off of steam flow is needed. The leakage has influence on the system efficiency. Paper presents the results of investigations of the ball valve tightness. The basic assumption needed to be verified was, whether the leakage through a seal after fatigue load will increase. The helium detector was used to determine the leakage volume in given time intervals. Very important assignment was to build a measuring facility which would enable leakage detection from the ball valve at helium overpressure range 0,1–4,5 MPa. Impact of the pressurized air on the closed ball was used as a fatigue factor. Impact could be used as a diagnostic procedure simulating exploitation conditions. Gas escaping around the ball was measured when element was new, then after 5 000 and finally after 10 000 pressure impacts. Experiment included also similar leakage measurement through a stuffing box.