Automated Tank Breathing

Abstract Our Terminal Operation is fully automated wherein tanks and pumps are assigned by the system and human interface is marginal. In automated operation we need to segregate the tanks and pumps to avoid cross contamination. Blocked sections of pipe are exposed to thermal expansion and activation of Pressure Relief valves (RV). This resulted in the pipes exposed to pressure cycles and product being released by RV. System developed to address the issue. Our Terminal operates on a start Stop mode. We identified the major Pipe sections which are responsible for the thermal expansion in the facility. These major Pipe sections were kept open to the same product tank at low level. This to ensure all thermal expansion in the pipe section are released to the tank. When the tank is designated for Breathing mode, then the tank is blocked by the system for any other operation to avoid the migration of undesired prodcucts to the tank. This is visually indicated in the screen to Alert the Operation Crew. The entire terminal handled four major products. Pipe sections were grouped based on product type. Major Pipe sections were identified in each group. Frequency of the pipe section being locked were analyzed and a statistical model was evolved to identify the pipe section which required to be kept in breathing. Once the Pipe sections were identified then the possible destination for these pipe sections were identified. For each destination the path is identifiedto allow assets within this path to be recognized. The current state of the asset is ascertained, e.g. is it available for operation or subject tomaintenance. If the asset is subject to maintenance, then alternate path is explored. The path selection criteria are based on the minimum number of assets which should be in the selected path. Once the path is chosen the asset and the tank is blocked for breathing for that particular blocked pipe section. In the event that the Pipe section, asset or Tank is required for Operation, then an alternate path is chosen for breathing. Any Pipe section that could be kept in breathing is alerted to the Terminal Operation crew, that at the earliest they need to keep the pipe section under breathing. This proposed approach intends to replace previous practices where the thermal expansion of the hydrocarbon was released to the closed blow down system, which resulted in loss of finished product. The pipe section was exposed to cyclic pressure cycle, which increased the fatigue in the pipes and rendering the pipes operating close to their design pressure each time the relief valve was operated. The simplicity and ease of operation is one of the key features offered by the proposed system. It also ensures the safety integrity of the Terminal assets.