Abstract: As per the Venting Atmospheric and Low-pressure Storage Tanks (API STD 2000-2014), and based on the engineering practices in China and abroad, relief rate required for safety facilities on lube oil tanks is calculated under over pressure and negative pressure. The relief rate calculation method for abnormal conditions is particularly discussed, and the relief rates of nitrogen regulator, relief valve and emergency relief manhole are determined. The results show that the maximum expiratory flow and maximum inspiratory flow of safety facilities under abnormal conditions are 876.3 m³/h and 501.8 m³/h respectively, both higher than the maximum fluid inflow and outflow under normal operations and the relief rate induced by atmospheric heating. In practice, all operational conditions of storage tanks should be analyzed one by one, in order to define the specification of safety facilities. The study results are instructive for design of safety facilities on storage tanks, especially those used in overseas projects.