Abstract: A shaft seal device comprises two mechanical seals for sealingly separating a sealed fluid region from an atmospheric region. A shaft is rotatable about an axis and extends through a casing from a sealed fluid region to an atmospheric region. The mechanical seals separate the sealed fluid region and the atmospheric region by a purge region formed between the mechanical seals. Each mechanical seal comprises a first seal ring fixed on the shaft and a second seal ring slidable in the axial direction and pressed against the first seal ring. The mechanical seal separating the sealed fluid region from the purge region is a contact type seal so that the fluid pressure of the sealed fluid region acts as a back pressure on the second seal ring. The mechanical seal separating the atmospheric region from the purge region is non-contact type seal so that the fluid pressure of the purge region acts as a back pressure on the second seal ring.

Abstract: This invention discloses an emergency shaft seal device wherein a packing ring of elastic material the inside diameter of which is larger than the outside diameter of a rotatable shaft is received in an annular groove along the periphery of the rotatable shaft to be free and not in contact with the rotatable shaft, and in the event of abnormal condition of a main shaft seal device used under the normal conditions, the packing ring is deformed by the pressure of a pressurized fluid applied to the outer periphery of the packing ring to be equally pressed to the periphery of the rotatable shaft so that the sealing is performed by the packing ring in place of main shaft seal.