A rotary union for providing a fluid connection between a rotating machine component and a non-rotating machine component, comprising: a rotating seal carrier adapted for connection to the rotating machine component, the rotating seal carrier having a rotating seal member connected thereon; a non-rotating seal carrier having a generally cylindrical shape, the non-rotating seal carrier having a non-rotating seal member connected thereon; the non-rotating seal carrier comprising a piston portion proximate the non-rotating seal member, the piston portion having a generally cylindrical shape with an enlarged diameter relative to the remaining portions of the non-rotating seal carrier; a flow restrictor ring having a generally annular shape disposed around the piston portion; a housing adapted for connection to the non-rotating machine component and forming a carrier bore into which the non-rotating seal carrier is slidably and sealably disposed such that, when the non-rotating seal carrier is at an extended position relative to the housing, the non-rotating seal member engages the rotating seal member to form a sliding face seal, the housing further forming a piston bore; a segmented media channel formed in the rotating and non-rotating seal carriers (101, 103), the segmented media channel being adapted to define a fluid passageway that conveys fluid media between the rotating and non-rotating machine components (108, 110) while the sliding face seal is present, wherein the segmented media channel is further adapted to be open for venting to the atmosphere when the rotating and non-rotating seal members (102, 104) are not engaged; wherein the enlarged diameter of the piston portion provides a net pneumatic or hydraulic surface that can be acted upon by a fluid at a positive or negative atmospheric pressure present within the piston bore of the housing, characterized in that the piston bore slidably accepts therewithin the piston portion and the flow restrictor ring such that a gap is formed in a radial direction between an outer diameter of the flow restrictor ring and an inner diameter of the piston bore. a rotating seal carrier adapted for connection to the rotating machine component, the rotating seal carrier having a rotating seal member connected thereon; a non-rotating seal carrier having a generally cylindrical shape, the non-rotating seal carrier having a non-rotating seal member connected thereon; the non-rotating seal carrier comprising a piston portion proximate the non-rotating seal member, the piston portion having a generally cylindrical shape with an enlarged diameter relative to the remaining portions of the non-rotating seal carrier; a flow restrictor ring having a generally annular shape disposed around the piston portion; a housing adapted for connection to the non-rotating machine component and forming a carrier bore into which the non-rotating seal carrier is slidably and sealably disposed such that, when the non-rotating seal carrier is at an extended position relative to the housing, the non-rotating seal member engages the rotating seal member to form a sliding face seal, the housing further forming a piston bore; a segmented media channel formed in the rotating and non-rotating seal carriers (101, 103), the segmented media channel being adapted to define a fluid passageway that conveys fluid media between the rotating and non-rotating machine components (108, 110) while the sliding face seal is present, wherein the segmented media channel is further adapted to be open for venting to the atmosphere when the rotating and non-rotating seal members (102, 104) are not engaged; wherein the enlarged diameter of the piston portion provides a net pneumatic or hydraulic surface that can be acted upon by a fluid at a positive or negative atmospheric pressure present within the piston bore of the housing, characterized in that the piston bore slidably accepts therewithin the piston portion and the flow restrictor ring such that a gap is formed in a radial direction between an outer diameter of the flow restrictor ring and an inner diameter of the piston bore.