AIR INGRESS INTO NITROGEN INERTED VENT PIPES

摘要

Providing a continuous flow of nitrogen through a vent pipe can avoid the ingress of air back down the vent. In the event of the nitrogen flow stopping air will enter the vent pipe. This could result in the loss of the inert gas blanket within the vented vessel if the nitrogen flow was not re-established quickly enough. Knowledge of how quickly air enters the vent pipe would be useful in devising a suitable corrective action plan. This paper presents the results of a series of experiments in which pipes of 1", 2", 4" and 6" nominal bore were inerted with nitrogen, the nitrogen flow stopped and the ingress of air into the pipes measured. Comparison of the experimental results with a theoretical model revealed that the predictions of the model were of the same order of magnitude as the experimental results for many of the test conditions. However, it was apparent that transient effects became dominant in situations where the vent pipe volume is small compared to the volume of the vessel.