Study for effective lighting protection system for floating roof tanks in petroleum refinery

Abstract

Refinery is considered as the foremost division of the Ceylon petroleum corporation which ensures the safety of the operation of process plant as well as for maintaining the required country’s demand for petroleum products to enhance the energy sector of the country. Since the un-interruptible continuous refinery operation is critically important to maintain national requirement of petroleum product and protecting the tanks and process equipment is essential. In this study, main concern about floating roof large crude oil storage tank facility. The most general method to prevent the possible damage to floating roof crude oil storage tank is using good earthing. The earthing system provides an electrical path to the ground and performance of the earthing system gets better as the earth loop impedance becomes lower. Since it is among the major concerns currently Refinery engineering staff is struggling with; and a proper method for reducing the sparks due to lightning mainly at critical locations were studied and simulations were done by using the floating roof tank model prepared by using PSCAD software which was validated with the actual model tank tested in the UOM laboratory. Direct and In-direct surge currents were calculated theoretically for 25 kA, 50 kA, 100 kA and 200 kA surges of 10/350 μS & 8/20 μS by applying calculated surge currents to the tank model. Finally, by analyzing all the results and the protection methods of different types of grounding devices were studied and proposed adjustable grounding conductor (AGC) with suitable locations as the optimum solution.