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Catalytic coking sites: upper part of the riser nozzle, upper space of the settler, surface of the centrifuge, oil transfer line, slurry circulation system. Preventive measures: use high-efficiency nozzles, install small nozzles symmetrically； The preheating temperature should be no lower than 200 degrees ； Atomized steam greater than 5% ； The temperature of the mixture of agent and oil should be no lower than 540 degrees ； Try to minimize the residence time of oil and gas, keeping it no more than 5 seconds ； Prevent scorching steam from reaching dead corners ； When starting up, use wax oil as much as possible; the injection temperature should be no lower than 530 degrees to prevent the formation of coking during startup ； Inspection and coking removal must be thorough ； Check that the lining has no hot spots, to prevent coking caused by dew point condensation ； The temperature at the bottom of the fractionation tower should not exceed 350 degrees; the density of the slurry should not be greater than 1.1 g/m3; the flow velocity in the slurry circulation line should be no less than 1.5 m/s. The pipelines in the slurry system must not be modified or thickened arbitrarily ； Make proper use of the slurry scale inhibitor; the stirring steam at the bottom of the distillation tower must be activated, and the residence time of the slurry at the bottom of the tower should be less than 5 minutes. Please add anything that was not mentioned.