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

A valve seal structure comprising:

• a seat adapted to contact, in a pressed state, a valve body attached inside a body via a stem so as to be freely opened and closed:
• a packing disposed between an outer periphery step part provided at a rear part of the seat and the body;
• and
• a pressing mechanism by which the packing is pressed towards a valve body, the pressing mechanism including a spring and a retainer gland pressed by a resilient force of the spring,
• the packing being provided with a contact surface for making 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 defining a space 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
• wherein, when a rear end part of the packing is pressed by the retainer gland, an inner diameter side of the packing advances into the space further than an outer diameter side of the packing, and a torsional action occurs between the inner diameter side and the outer diameter side of the packing with:
• an inner diameter side of the rear end part of the packing functioning as a point of effort:
• the contact surface of the packing functioning as a fulcrum;
• and
• a tip outer peripheral region of the packing functioning as a point of load.

A valve packing capable of sealing when 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 opened and closed and the body, the valve packing comprising:

• a contact surface for making contact with a step part surface of an outer periphery step part of the seat is provided on a tip outer diameter side of the packing;
• and
• a non-contact part that does not make contact with the seat is provided on a tip inner diameter side of a packing tip surface other than the contact surface.
• wherein, when a rear end part of the packing is pressed by a pressing force of a pressing mechanism, an inner diameter side of the packing will advance in a direction toward the seat more than an outer diameter side of the packing, and a torsional action occurs between the inner diameter side and the outer diameter side of the packing with:
• an inner diameter side of the rear end part of the packing functioning as a point of effort:
• the contact surface of the packing functioning as a fulcrum;
• and
• a tip outer peripheral region of the packing functioning as a point of load.