Roof drain system is one of the key components in ensuring safety and reliable performance of floating roof tanks. It is the main conduit for the drainage of the accumulated water/fluid on top of the roof of the external floating roof tanks. Over the years the design of roof drain system has evolved from simple gland packing type swivel joints to ball bearing type swivel joints, flexible joint type, flexible steel hose pipe (Co-flex pipe) and so on. The moving parts and the attached accessories of the roof drain system are subjected to continuous stresses due to the cyclic filling and unloading of the tank, thereby making them susceptible to failure. Failure of the roof drain system can jeopardize the overall safety of tanks as it can lead to product spillage, roof sinking and other serious environmental hazards. Furthermore, as the roof drain system is inacces- sible while the tank is in operation, it would be required to shutdown and clean the tank in order to carry out suitable repairs to the roof drain system. A study was undertaken to evaluate the performances of different types of roof drain systems used in storage tanks at Kuwait Oil Company. Comprehensive data was collected with regard to the service life, failure frequency of the components, impact of failures and causes of failures. “What if” analysis & Failure Mode & Effect Analysis (FMEA) were carried out highlighting the adverse effects of roof drain system failure. This paper discusses the selection, design and maintenance of the roof drain system in the best possible manner to minimize or avoid any unexpected failures during normal operation leading to a hazardous situation.
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