Trunnion-type ball valve, valve seal structure, and valve packing

A trunnion-type ball valve in which a ball provided inside a body is rotatably provided via upper and lower stems and is sealed with a ball seat to be contacted in a state of being pressed to the ball, the trunnion-type ball valve having a packing attached to a space between an outer periphery step part provided at a rear part of the ball seat or a rear part of a seat retainer to which the ball seat is attached and the body and a pressing mechanism by which this packing is pressed to a ball direction and being provided with a contact surface to make contact with a step part surface of the outer periphery step part on a tip outer diameter side of a tip surface of the packing and a non-contact part configuring a space provided between the packing and the step part surface of the outer periphery step part on a tip inner diameter side of the packing tip surface other than the contact surface and, in a state in which a torsional action is caused to act on the packing at least by a pressing force of the pressing mechanism, a tip outer peripheral region of the packing being locally press-contacted to the body to raise a seal surface pressure.

A valve seal structure in which a seat in a pressed state is contacted with a valve body attached inside a body via a stem so as to be freely open and closed, the structure having a packing attached to a space between an outer periphery step part provided at a rear part of the seat or a rear part of a seat retainer to which the seat is attached and the body and a pressing mechanism by which this packing is pressed to a valve body direction and being provided with a contact surface to make contact with a step part surface of the outer periphery step part on a tip outer diameter side of the packing and a non-contact part configuring a space provided between the packing and the step part surface of the outer periphery step part on a tip inner diameter side of a packing tip surface other than the contact surface and, in a state in which a torsional action is caused to act on the packing at least by a pressing force of the pressing mechanism, a tip outer peripheral region of the packing being locally press-contacted to raise a seal surface pressure.

A valve packing capable of sealing as being attached to a space between a rear part of a seat in a pressed state to be contacted with a valve body attached inside a body of a valve via a stem so as to be freely open and closed or an outer periphery step part provided at a rear part of a seat retainer to which a seat is attached and the body, wherein a contact surface to make contact with a step part surface of the outer periphery step part is provided on a tip outer diameter side of this packing, a non-contact part with the seat or the seat retainer is provided on a tip inner diameter side of a packing tip surface other than the contact surface and, in a state in which a torsional action is caused to act on the packing itself at least by a pressing force of a pressing mechanism, a tip outer peripheral region of the packing is a portion where a seal surface pressure is raised.