A damper for dampening rotation of a dipper door relative to a dipper body of a mining shovel includes a shaft, an arm, and a high pressure fluid seal. The shaft supported for rotation about a shaft axis, and rotation of the shaft is dampened by fluid in an enclosed chamber. The high pressure fluid seal engages an outer surface of the shaft at a position between the first end of the shaft and the second end of the shaft. The high pressure fluid seal engages an outer surface of the shaft and includes a low pressure side and a high pressure side adjacent a shaft cavity. The arm includes a first end coupled to the first end of the shaft, and a second end coupled to the dipper door or the dipper body such that rotation of the dipper door drives the arm to rotate the shaft.