Adjustable choke valve

Claim 2

A choke valve comprising: a. a housing having an inlet and an outlet, b. a first disc fixedly mounted within said housing between said inlet and said outlet and having an aperture therein, c. a second disc rotatable mounted within said housing, one face of said first disc contacting and mating with one face of said second disc, said second disc having an aperture therein which periodically passes in registry with said aperture in said first disc when said second disc is rotated, d. a coating of dense, impermeable material having a hardness of at least 2,700 on the Knoop scale and having a variation in surface flatness of less than six helium light bands covering the mating surfaces of said first and second discs, said discs being comprised of: e. steel carrier plates having recesses in said mating surfaces, and f. insert members secured within said carrier plates, said insert members comprising bodies of graphite having a coating of silicon carbide on the exposed surface thereof.

Claim 3

A choke valve as defined in claim 1 wherein the exposed surfaces of said carrier plates are covered with a dense impermeable coating of titanium carbide.

Claim 4

In an adjustable choke valve having a housing with an inlet and an outlet, a choke disc having at least one aperture therein positioned between said inlet and said outlet, a follower disc abutting said choke disc and rotatable with respect thereto, said follower disc also having at least one aperture passing therethrough and positioned to periodically pass in registry with said aperture in said choke disc as said follower disc is rotated, and means for rotating said follower disc, the improvement comprising: a. a choke disc and a follower disc having depressions in the abutting surfaces thereof; b. bodies secured within said depressions in said choke disc and said follower disc, said bodies having a coating of dense, impermeable material having a thickness of at least 0.005 inch and a hardness of about 2,740 on the Knoop scale covering the mating surfaces of said bodies, said mating surfaces further being parallel to + or - 0.002 inch and having a variation in surface flatness of less than six helium light bands; and c. said bodies being comprised of graphite coated with a continuous layer of silicon carbide intimately bonded to said graphite.

Claim 5

In an adjustable choke valve having a housing with an inlet and an outlet, a choke disc having at least one aperture therein positioned between said inlet and said outlet, a follower disc abutting said choke disc and rotatable with respect thereto, said follower disc also having at least one aperture passing therethrough and positioned to periodically pass in registry with said aperture in said choke disc as said follower disc is rotated, and means for rotating said follower disc, the improvement comprising: a. a choke disc and a follower disc having depressions in the abutting surfaces thereof; b. bodies secured within said depressions in said choke disc and said follower disc, said bodies having a coating of dense, impermeable material having a thickness of at least 0.005 inch and a hardness of about 2,740 on the Knoop scale covering the mating surfaces of said bodies, said mating surfaces further being parallel to + or - 0.002 inch and having a variation in surface flatness of less than six helium light bands; and c. said bodies being comprised of graphite coated with a continuous layer of silicon carbide intimately bonded to said graphite.