Abstract: A mechanical seal having two balance diameters and balance factors established separately and freely for two fluids which are opposed at a sealing face by providing two seal packings with a seal ring. A sidewall of a packing groove is removed on the sealed fluid side when the sealed fluid contains crystal deposits or solid substances, and a vacuum path is connected between the two seal packings. Also, a seal ring can be divided between the two seal packings into two parts so as to provide flexibility against deflection in a radial direction.

Abstract: A pressurizing device for a pump seal includes a cylindrical chamber fitted over an extension of a pump shaft external of the seal with a sliding piston inside the chamber being mounted for reciprocation relative to the external shaft portion in dividing the space in the cylinder into high pressure and low pressure chambers with the high pressure chamber communicating with the seal. A screw pump consisting of a pumping thread on the shaft is positioned in a bore axially extending through the piston with rotation of the shaft effecting pumping through a check valve to the high pressure chamber from the low pressure chamber so as to cause the piston to move toward the low pressure chamber and compress a compression spring mounted in the low pressure chamber. The compression spring urges the piston toward the high pressure chamber so as to always maintain high pressure in the high pressure chamber after the pump operation and consequent rotation of the shaft is terminated.