A seal apparatus for a casing of a turbomachine, comprising: an annular body having a center axis and defining a central opening extending along the center axis, the annular body further comprising a first annular body portion comprising a first annular sidewall, a second annular sidewall axially opposing the first annular sidewall, and an outer annular surface extending between the first annular sidewall and the second annular sidewall; a second annular body portion extending axially from the first annular body portion and having an outer annular surface radially offset from the outer annular surface of the first annular body portion; and an appendage extending axially from the first annular body portion and having an outer annular surface and an inner annular surface, the inner annular surface of the appendage and the outer annular surface of the second annular body portion defining an annular cavity therebetween, and at least a portion of the appendage is configured to be displaced radially outward in order to maintain contact with a first inner cylindrical surface of the casing and a second inner cylindrical surface of the casing during radial expansion of the casing; wherein a plurality of annular seals (106, 108, 110) are disposed in respective annular grooves (100, 102, 104) defined by the outer annular surface of the appendage, at least a portion of each of the plurality of annular seals (106, 108, 110) extending radially outward from the respective annular groove (100, 102, 104) and configured to sealingly engage the first inner annular surface of the casing, characterized in that the outer annular surface of the appendage further defines a port disposed between the adjacent annular seals (106, 108, 110) and configured to be fluidly coupled to a lower pressure environment, and the adjacent annular seals (106, 108, 110) are a primary annular seal and a secondary annular seal (108, 110), wherein the primary annular seal is disposed in an annular groove proximal to an end portion of the appendage distal to the first annular body portion, wherein the secondary annular seal (108, 110) is disposed in an annular groove (102, 104) distal to the end portion, wherein the primary annular seal has a greater external diameter than the secondary annular seal (108,110), and wherein the annular groove, in which the primary annular seal is disposed, is greater in size than the annular groove (102, 104) in which the secondary annular seal (108, 110) is disposed. an annular body having a center axis and defining a central opening extending along the center axis, the annular body further comprising a first annular body portion comprising a first annular sidewall, a second annular sidewall axially opposing the first annular sidewall, and an outer annular surface extending between the first annular sidewall and the second annular sidewall; a second annular body portion extending axially from the first annular body portion and having an outer annular surface radially offset from the outer annular surface of the first annular body portion; and an appendage extending axially from the first annular body portion and having an outer annular surface and an inner annular surface, the inner annular surface of the appendage and the outer annular surface of the second annular body portion defining an annular cavity therebetween, and at least a portion of the appendage is configured to be displaced radially outward in order to maintain contact with a first inner cylindrical surface of the casing and a second inner cylindrical surface of the casing during radial expansion of the casing; wherein a plurality of annular seals (106, 108, 110) are disposed in respective annular grooves (100, 102, 104) defined by the outer annular surface of the appendage, at least a portion of each of the plurality of annular seals (106, 108, 110) extending radially outward from the respective annular groove (100, 102, 104) and configured to sealingly engage the first inner annular surface of the casing, characterized in that the outer annular surface of the appendage further defines a port disposed between the adjacent annular seals (106, 108, 110) and configured to be fluidly coupled to a lower pressure environment, and the adjacent annular seals (106, 108, 110) are a primary annular seal and a secondary annular seal (108, 110), wherein the primary annular seal is disposed in an annular groove proximal to an end portion of the appendage distal to the first annular body portion, wherein the secondary annular seal (108, 110) is disposed in an annular groove (102, 104) distal to the end portion, wherein the primary annular seal has a greater external diameter than the secondary annular seal (108,110), and wherein the annular groove, in which the primary annular seal is disposed, is greater in size than the annular groove (102, 104) in which the secondary annular seal (108, 110) is disposed.