A Practical Method to Study Over and Under-Pressurizing of Ship Tanks During Ballasting and Deballasting

There have been many incidents of hull damage due to over and under-pressurizing of ship tanks during ballasting and deballasting. A safety relief hole of 6 to 8mm diameter is generally provided in Air-pipes to prevent accidental over and under-pressurizing of ship tanks during ballasting and deballasting. This paper investigates the pressure rise and drop inside the tank assuming the air-pipe to be closed. A practical method based on Computational Fluid Dynamics has been presented to find out the maximum pressure rise or drop. A parametric study, based on varying relief hole diameter, has been carried out. The investigation brings to prospective the extent of pressure rise or drop, and hence the damages that can occur due to poor operation of the Air-pipes during ballasting and deballasting and a need for automated opening and closing of the Air-pipes for a safer ship.