A seal device is adapted to be interposed and compressed between joined pieces in a flow line that is operative to convey a flowing fluid. The seal device comprises an inner seal member and an outer seal retainer member. The inner seal member has a central opening extending therethrough to accommodate the flow of the fluid and has a channel structure that provides a channel opening which faces the central opening and extends therearound. A pair of lips are disposed opposite each other and extend around an inner peripheral portion of the inner seal member. The lips operate to apply a sealing force against the joined pieces when interposed and compressed therebetween. The outer seal retainer member surrounds the inner seal member. The inner seal member and the outer seal retainer member are sized and adapted to seal a space between the joined pieces in the flow line when interposed and compressed between the joined pieces to allow fluid to flow therethrough. The inner seal member is operative to prevent contact of the fluid with the outer seal retainer member when interposed and compressed between the joined pieces. Where the fluid is corrosive, the inner seal member includes a portion formed of anti-corrosive material. Auxiliary resilient spacers and springs may be employed with the inner seal member.