Sliding-gate valve

In a valve assembly, the combination of:

• a valve body defining a circular bore extending about a first axis,
• a seat assembly coaxially fitted in said bore and defining a flow channel, said seat assembly comprising first and second seat rings cooperatively defining an annular gap which together with opposed passages in said body forms a guideway extending along a second axis normal to the first axis, the first seat ring being slidably and sealably engaged with said body, the second seat ring being press-fitted in but not affixed to said body;
• a third ring disposed outwardly of and bearing on the first seat ring, the third ring being cut away at spaced-apart locations to receive inwardly slidable wedge-shaped inserts for displacing the first seat ring toward the second seat ring when said inserts are forced inward toward said channel;
• and a fourth ring affixed to said body for preventing displacement of the second seat ring in a direction away from the first seat ring.

A valve assembly comprising:

• a valve body defining a circular bore extending about a first axis and also defining opposed passages intersecting said bore and extending along a second axis substantially normal to the first;
• an annular seat assembly coaxially fitted in said bore and defining a flow channel, said assembly comprising rings disposed along the first axis, said rings including first and second seat rings cooperatively defining an annular gap communicating with said passages to form a guideway extending along the second axis, the first seat ring being slidably and sealably engaged with said body;
• the second seat ring being tightly fitted in but not affixed to said body;
• a third ring disposed outwardly of and bearing on the first seat ring, the third ring being affixed to said body;
• a fourth ring affixed to said body for preventing displacement of the second seat ring in a direction away from the first seat ring;
• and inwardly slidable wedge-shaped inserts positioned between the first seat ring and the second seat ring for displacing the first seat ring toward the second seat ring;
• a valve casing supporting said body and including chambers extending in opposite directions from said body along the second axis, said chambers communicating respectively with said passages and being sealed from atmosphere;
• a plate-type gate mounted for reciprocation in said guideway between positions where a portion of said gate closes said channel and where a generally circular aperture in said gate is in register with said channel, and
• means respectively extending into said chambers for introducing therein purge gas at a pressure exceeding the pressure within said channel.