Valve device having stationary and movable or turnable valve bodies

Abstract: The invention provides an erosion resistant pressure reduction valve or choke comprising a valve housing (1,22) defining a valve chamber (2) connected with an inlet (3) and outlet (4), a stationary first valve body (6,17) arranged in the chamber, and a second valve body (7,18). The second valve body is arranged so as to be turnable or displaceable relative to the first valve body by means of a spindle or the like (14,23). The first and second valve bodies are each provided with corresponding flow-through apertures (19,28). Flow through the valve is regulated by turning or displacing the turnable/displaceable second valve body relative to the first. The apertures in the valve bodies (6,7,17,18) are provided with casings (15,20) made in one piece of polycrystalline diamond.

Description: The present invention provides a pressure reduction valve or choke which retards erosion. The inventive valve comprises a valve housing defining a valve chamber connected to an inlet and an outlet, and a stationary first valve body provided in the chamber. In connection with the exploitation of oil and gas, pressure reduction valves or chokes are used to control the pressure and the stream of oil and gas from subterranean reservoirs. Usually, these chokes sit in a christmas tree of a particular oil well. They are arranged so as to be demounted for maintenance or replacement. The chokes often operate under very difficult conditions of high temperature and pressure and with high current velocities. Often, the oil and gas contain sand particles; erosion may frequently be extreme in exposed parts of the chokes. Consequently, these parts or entire chokes have to be replaced after a short time. Replacement and maintenance of the chokes is risky because of the high pressure under which they operate. Special safety precautions must be taken to reduce the danger of pollution to the surroundings and to avoid injury to persons doing the maintenance and replacement. When oil and gas are exploited at great subsea depths, chokes are arranged on a christmas tree connected to seabed structures. Replacement and maintenance of the chokes in such installations is particularly risky and demanding, and the costs are high. Clearly, extension of the choke lifetime can achieve reduced replacement/maintenance costs. Therefore, efforts have been made to develop regulatable chokes with erosion-resistant properties. U.S. patent No. 4,732,364 discloses a choke in the form of a valve seat with a turnable, with an axially displaceable pin extending into a casing arranged in a valve housing. The pin has a conical portion corresponding to a complementary conical portion in the casing. The conical portions of the pin and casing are coated with polycrystalline diamond tiles to increase erosion resistance. By turning the pin, the fluid stream through the valve is regulated. The valve can be completely closed by turning the pin such that a projecting part of the pin rests against seat-shaped part at the upper end of the casing. The valve disclosed in this patent has not found any practical application since the tiles loosen and fall off. The valve is also expensive to make, both because the large number of specially designed tiles are expensive to produce and because painstaking work is required to bond the tiles. An object of the present invention is to provide a choke or pressure reduction valve with a substantially longer lifetime, i.e. which is substantially more erosion resistant than conventional valves. Another object is to provide a pressure reduction valve substantially cheaper to make and simpler to maintain. The inventive valve is characterized in that a second valve body is arranged so as to be turnable or displaceable relative to the first valve body by means of a spindle or the like, wherein the first and second valve bodies are each provided with corresponding flow-through apertures whereby flow through the valve is regulated by turning or displacing the turnable/displaceable second valve body relative to the first, and that the apertures in the valve bodies are provided with casings made in one piece of polycrystalline diamond. Dependent claims 2-6 define advantageous features of the invention. The invention shall now be described with an example and with reference to the attached drawing, in which Fig. 1 shows a vertical and horizontal section (along line A-A) of an embodiment of the inventive choke, Fig. 2 shows in cross section and a overhead view of a casing provided in accordance with the invention, and Fig. 3 shows a vertical and horizontal section (along line B-B) of an alternate embodiment of the inventive valve. Fig. 1 shows as previously stated vertical and horizontal sections of the inventive valve. The valve comprises a valve housing 1 defining a valve chamber 2 connected with an inlet 3 and a outlet 4. A substantially cylindrical stationary first valve body 6 is arranged in the valve chamber 2. The stationary valve body 6 is provided with radial apertures 5. Valve body 6 is fixed to the valve housing 1 by a bushing 12 pressed downwardly by a closure 13. A second valve body 7 is arranged inside the stationary valve body 6. A valve spindle 14 can axially displace the second valve body. The axially displaceable valve body 7 is adapted to the interior shape of the stationary valve body 6, and is provided with apertures 8 corresponding to apertures 5 in the stationary valve body 6. The stream of fluid through the inventive valve can be regulated by displacing the second valve body 7 in an axial direction by means of the spindle 14 such that the flow-through area between the apertures is increased or decreased. The inventive valve can be completely shut by displacing the second valve body 7 and thereby the apertures 8 past apertures 5 in the stationary valve body 6. The essence of the invention is that the apertures 5 and 8 in the valve bodies 6 and 7 are provided with casings 15 made of one-piece polycrystalline diamond. The casings 15 can be fastened to the valve bodies 6,7 by a shrinking on process, soldering or in another manner. The casings 15 made of this material can be advantageously anchored as shown in Fig. 2 to exterior casings or rings 16 of wolfram carbide or similarly suitable material. Fig. 3 shows an alternatively shaped inventive valve based on the same principle but somewhat different from the previously described embodiment. The difference is that instead of valve bodies 6,7 with radial apertures, two discs are used, one being a lower stationary disc 17 and the other an upper rotatable disc 18. Each disc 17,18 is provided with axially corresponding apertures 19 with casings 20 of polycrystalline diamond. The discs are arranged in a valve-stem guide 21 in the valve housing 22. The upper disc 18 can be rotated by means of a valve spindle 23 rotatable arranged in a closure 24. By rotating the upper disc 18 relative to the lower disc 17, flow through quantity can be regulated or alternatively the valve can be closed. Access to the valve chambers for both inventive valve embodiments shown in Figs. 1-3 is simply attainable by screwing off (demounting) the closures 13 and 24. Thus, the valve bodies are easily removable and replaceable during maintenance. To reduce erosion of particularly exposed parts of the valve, it may be desirable to furnish these parts with erosion-resistant material. In Figs. 1 and 3, examples are illustrated with the valve body 6 and guide 21 are provided with wolfram carbide plates 25,26 coated with a diamond layer in accordance with the vapor deposition method. In the drawings, inventive valves are shown with four apertures. With respect to the invention as defined in the claims, the inventive valves can be provided with larger, fewer or more apertures, depending upon desired capacity, pressure conditions, etc. Similarly, the number of casings 20 in the direction of the flow can be more than one.

Claims: An erosion resistant pressure reduction valve or choke comprising a valve housing (1,22) defining a valve chamber (2) connected with an inlet (3) and outlet (4), a stationary first valve body (6,17) arranged in the chamber, characterized in that a second valve body (7,18) is arranged so as to be turnable or displaceable relative to the first valve body by means of a spindle or the like (14,23), wherein the first and second valve bodies are each provided with corresponding flow-through apertures (19,28) whereby flow through the valve is regulated by turning or displacing the turnable/displaceable second valve body relative to the first, and that the apertures in the valve bodies (6,7,17,18) are provided with casings (15,20) made in one piece of polycrystalline diamond. The valve of claim 1, characterized in that the casings of polycrystalline diamond are anchored to exterior casings (16) of wolfram carbide, stainless steel or another suitable material. The valve of claims 1 and 2, characterized in that the valve bodies are constituted by two substantially concentric cylinders (6,7) having radially arranged apertures (5,8), wherein the outer cylinder (6) is stationary, while the inner cylinder (7) is axially moveable. The valve of claim 1 and 2, characterized in that the valve bodies are constituted by two discs with apertures (19,28) extending through the discs, wherein the one disc (17) is stationarily arranged in a valve stem guide (21), while the other (18) is rotatable arranged on the stationary disc. The valve of preceding claims 1 through 4, characterized in that the valve bodies are provided with one or a plurality of successive casings (15,20) of polycrystalline diamond in the direction of the flow. The valve of preceding claims 1 through 4, characterized in that the valve bodies are provided with in the direction of the flow one or a plurality of successive casings of wolframcarbide, acid resistant steel or similar erosion resistant material.

Inventors: NOKLEBERG LARS, SKYLLINGSTAD OLAV, SONTVEDT TERJE, NOKLEBERG, LARS, SKYLLINGSTAD, OLAV, SONTVEDT, TERJE
Applicants: NORSK HYDRO AS, NORSK HYDRO A.S.
Application year: 1992
Main classification: F16K25
IPC codes: F16K25, E21B34