Patent ID: 6874759

Claim:
A plug valve comprising: a main valve body having a first passage, a second passage, and a first opening intersecting said first passage and said second passage, said first opening having a cylindrical surface; a plug member provided with a communication hole for communicating with said first passage and said second passage, said plug member being rotatable between a communication position for connecting said communication hole to said first passage and said second passage and an interruption position for interrupting communication between said first passage and said second passage; a seal member provided on said plug member for surrounding an opening end of said communication hole; and a seal-retaining member provided in said first passage and having a second opening, wherein slits or holes communicating with said first opening are provided in said seal-retaining member, said seal-retaining member having a cylindrically curved surface corresponding to said cylindrical surface of said first opening and conforming to an outer circumferential surface of said plug member, wherein said seal member is prevented from projecting by said seal-retaining member when said plug member rotates and said seal member crosses said first passage.