The invention is a catalyst injection system and method for injecting catalyst. In one embodiment, a fluid catalytic injection system includes vessel configured to store one or more catalysts, a pressure transmitter, a pressure control valve, a discharge valve, and a controller. The pressure control valve is coupled to the vessel and regulates the gas pressure therein. The discharge valve is coupled to the vessel and controls a discharge of catalyst from the vessel. The pressure transmitter provides a metric of pressure to the controller as an input. The controller contains instructions, that when executed, prevents the simultaneous opening of the pressure control valve and the discharge valve. In another embodiment, a method for injecting catalyst into a fluid catalytic cracking unit is provided. The method includes regulating pressure within a catalyst storage vessel, changing an amount of catalyst in the storage vessel, and preventing a simultaneous occurrence of the regulating and changing steps.