Hydrodynamic face seal with grooved sealing dam for zero-leakage

In a mechanical seal for sealing an annular sealing space between a housing and a rotatable shaft which extends axially, said mechanical seal including a first seal ring mounted non-rotatably to said housing and a second seal ring rotatably connected to said shaft so as to rotate therewith, one of said first and second seal rings being axially movable relative to the other of said first and second seal rings and having a biasing arrangement which biases said one seal ring axially toward the other, said first and second seal rings having opposing seal faces disposed in sealing relation with each other to define a sealing region extending radially along said seal faces, said seal faces being relatively rotatable and axially separable during shaft rotation such that a liquid film is defined therebetween within said sealing region, comprising the improvement wherein one of said seal faces includes hydrodynamic lift features which comprise a plurality of circumferentially spaced apart recesses, each said recess extending radially away from a first end thereof near a first circumferential boundary of said sealing region and toward an interior second end, a film liquid being disposed between said seal faces, and said recesses receiving said film liquid therein and generating hydrodynamic lift within said sealing region during shaft rotation to control separation of said seal faces, said liquid film extending radially uninterrupted between said first and second ends of said recesses to hydrodynamically counteract said biasing arrangement for stable non-contacting separation of said seal faces, one of said seal faces further including a plurality of annular grooves disposed radially between a second boundary of said sealing region opposite said first boundary and said interior second ends of said hydrodynamic recesses, said grooves having a shallow depth and being separated one from the other by annular lands extending radially therebetween, said grooves and said lands being configured such that gas in said liquid film separates therefrom during shaft rotation and collects in said grooves while liquid is retained along said lands, alternating rings of said gas and said film liquid being formed during shaft rotation by the configuration of said grooves and said lands to define a leakage barrier during shaft rotation which prevents movement of said film liquid radially across said annular grooves to prevent leakage of said film liquid from said second boundary.

In a mechanical seal having first and second seal rings which are disposed one next to the other along a rotating member adjacent to a seal chamber having a sealed fluid therein, said seal rings having respective opposing seal faces which define a radial sealing region therebetween which prevents leakage of said sealed fluid along said rotating member, said seal rings being relatively rotatable during rotation of said rotating member, comprising the improvement wherein said sealing region includes an annular grooved seal face region and an annular hydrodynamic seal face region disposed radially next to said grooved seal face region, said seal faces being in contacting relation in the absence of shaft rotation, and a film liquid being supplied to said hydrodynamic seal face region during shaft rotation, said hydrodynamic seal face region including hydrodynamic lift features formed in one of said seal faces wherein said hydrodynamic lift features receive said film liquid and generate a liquid film that is disposed axially between said seal faces and extends radially within said sealing region during shaft rotation, said liquid film defining a lift load which maintains said seal faces in axially spaced, non-contacting relation during shaft rotation, said grooved seal face region including a plurality of annular concentric grooves formed in one of said seal faces wherein said grooves are radially spaced apart from each other by seal face lands extending radially therebetween and receive said film liquid during shaft rotation, said grooves and said lands being configured such that gases in said film liquid separate therefrom during shaft rotation and collect within said plurality of grooves, said lands having film liquid disposed between each said land and said seal face opposite thereto wherein said concentric grooves define a plurality of liquid-gas interfaces spaced radially apart from each other across said grooved seal face region to support a radial pressure gradient between inner and outer diameters of said grooved seal face region to prevent leakage of film liquid radially from said hydrodynamic seal face region across said grooved seal face region.