Rotary union with bellows seal

A method for operating a rotary union, comprising:

• providing a housing having a fluid inlet;
• rotatably supporting a rotating machine component in the housing, the rotating machine component having a rotating seal member associated therewith;
• providing a slidably and sealably mounted non-rotating seal member in the housing adjacent the rotating seal member;
• engaging the non-rotating seal member and the housing with an expandable seal, wherein the expandable seal includes two end portions, one of the two end portions engaged to the non-rotating seal member and the other of the two end portions engaged to the housing, and an expandable portion disposed axially between the two end portions;
• selectively providing a fluid medium in the housing at a pressure to expand or contract the expandable portion of the expandable seal based on the pressure and a medium type;
• wherein engaging the non-rotating seal member and the housing with the expandable seal includes engaging each of the two end portions in a corresponding bore formed in the non-rotating seal member and the housing.

A rotary union, comprising:

• a rotating seal member;
• a non-rotating seal member that is reciprocally disposed in a housing;
• a media channel extending through the housing, the non-rotating seal member and the rotating seal member;
• and
• an expandable seal that includes at least one convolution, wherein the convolution is configured to expand under fluid pressure and axially displace the non-rotating seal member towards the rotating seal member until the non-rotating seal member sealably engages the rotating seal member along a mechanical face seal interface defined between the rotating seal member and the non-rotating seal member;
• wherein the convolution is further configured to provide a biasing force tending to push the non-rotating seal member towards the rotating seal member and to create a compressive force along the mechanical face seal interface during operation based on a pressure and a type of fluid present in the media chamber;
• wherein the expandable seal includes two convolutions;
• and
• wherein the expandable seal includes two straight, end portions disposed on either axial side of the two convolutions, each of the two straight, end portions radially engaging a corresponding bore formed in each of the housing and the non-rotating seal member.