GATE VALVE STRUCTURE AND PRODUCTION METHOD THEREFOR

Abstract

With the simple cylindrical body shape of gate valves that are currently on the market, the welded portions have three-dimensionally curved shapes and welding is difficult for general purpose welding machines. Moreover, in manufacture by casting, there are many defects in the material such as cavities and sand trapping, and man-hours and cost are necessary to repair same. In the gate valve according to the present invention, a body has openings to accommodate two connecting pipes and a gate. The two connecting pipes respectively pass through the two openings and are disposed so as to face the gate from two sides. The two connecting pipes are each joined to the body by welding at an opening and the shape of said welded sections is a circular ring. Moreover, when producing the body in the present invention, the body portion is manufactured by forging instead of casting and after machining, is unified by welding.

Claims

1-6. (canceled)

7. A gate valve comprising: a hand wheel, a stem, a gate, a body, and two connection pipes, the gate valve being configured to control a flow of a fluid, wherein the body has a first opening and a second opening for accommodating each of the two connection pipes, and a third opening for accommodating the gate, protrusions each having a circular-ring shape are provided on an outer circumference of each of the two connection pipes, and an outer circumference of each protrusion is configured to match to each inner circumference of the first opening and the second opening, each of the two connection pipes passes through the first opening and the second opening, each end of the two connection pipes being disposed opposed from both sides of the gate, and each of the two connection pipes is jointed to the body by welding each of the outer circumferences of the protrusions and each of the inner circumferences of the first opening and the second opening.

8. The gate valve according to claim 7, wherein at least a circumferential portion of the first opening and the second opening of the body has part of a sphere in shape.

9. The gate valve according to claim 7, wherein at a circumferential portion of the first opening and the second opening of the body has part of a circular cone in shape.

10. A method for producing a gate valve including: a hand wheel, a stem, a gate, a body, and two connection pipes, the gate valve being configured to control a flow of a fluid, the method comprising: producing a plurality of divided body portions of the body by forging; welding the plurality of divided body portions to form the body; forming first and second openings each having a circular shape on side faces of the body to allow disposition of each end of the two connection pipes opposed from both sides of the gate; forming protrusions each having a circular-ring shape are provided on an outer circumference of each of the two connection pipes; and joining each of the outer circumferences of the protrusions of the two connection pipes to each of inner circumferences of the first opening and the second opening which match to the outer circumferences by welding.

11. The method for producing the gate valve according to claim 10, wherein the forming the openings on the side face of the body is performed by machining.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1A is a perspective view of a structure of a conventional gate valve (a portion of a body, a connection pipe, or the like is not given).

[0020] FIG. 1B is a cross-sectional view of the conventional gate valve.

[0021] FIG. 2A is a top view of a joint portion between a cylindrical body and a connecting pipe portion of a conventional cast gate valve.

[0022] FIG. 2B is a perspective view of the joint portion between the cylindrical body and the connecting pipe portion of the conventional cast gate valve.

[0023] FIG. 2C is a cross-sectional view of the joint portion between the cylindrical body and the connecting pipe portion of the conventional cast gate valve.

[0024] FIG. 3A is a top view of a joint portion between a spherical body and a connecting pipe portion according to the present invention.

[0025] FIG. 3B is a side view of the joint portion between the spherical body and the connecting pipe portion according to the present invention.

[0026] FIG. 3C is a front view of the joint portion between the spherical body and the connecting pipe portion according to the present invention.

[0027] FIG. 4A is a divided view of a body spherical portion according to the present invention.

[0028] FIG. 4B is a welded view of the body spherical portion according to the present invention.

[0029] FIG. 4C is a processed view of the spherical portion according to the present invention.

[0030] FIG. 4D is a welded view of a connecting pipe portion and a connection pipe according to the present invention.

[0031] FIG. 4E is a welded view of the connecting pipe portion and a body lower portion according to the present invention.

[0032] FIG. 5 is a cross-sectional view of a connection pipe weld portion according to the present invention at non-destructive inspection.

FIRST EMBODIMENT

[0033] When a body is fabricated by forging, a body having an axially symmetric shape can be easily produced by ring forging and die forging. However, both ring forging and die forging are difficult to from a thin body or a body having a large length/diameter ratio. In order to facilitate forging, as illustrated in FIG. 4A, a body is divided at a connecting pipe portion to reduce the length/diameter ratio. Dividing the body enables die forging of a bulge of a body central portion and use of materials close to the final form, so that material cost can be reduced.

[0034] A steel material with 0.1 to 0.4% carbon is used and body portions 40 and 41 are hot forged at 1000 to 1500 C. Then, heat treatment (quenching and annealing) is performed as necessary. The hemispherical body portions 40 and 41 are welded as illustrated in FIG. 4B, and then openings 42 for inserting a connection pipe are fabricated both sides of the body, respectively by machining (FIG. 4C). For example, each opening 42 is machined by cutting into a circular shape and cutting as it is with a U-axis machining center.

[0035] Next, as illustrate in FIG. 4D, connection pipes 45 and 46 are respectively inserted into the fabricated openings 42 opposed to each other and then welded. At this time, since a circumferential portion 44 at which a connection pipe of the body is to be inserted is formed in a spherical shape, a weld portion 43 has a circular-ring shape in a horizontal plane. Therefore, just maintaining the angle of the welding torch and the workpiece of interest at a constant angle and rotating the workpiece of interest in the horizontal plane enables easy welding. Note that, in order to make the shape of a weld portion a circular-ring shape in the horizontal plane, in addition to making the shape of the circumferential portion 44 spherical, the circumferential portion 44 may be made into a circular cone shape at which the rotary shaft agrees with the axis of the connection pipe, or may be into a different curved shape at which the rotary shaft agrees with the axis of the connection pipe.

[0036] Next, as illustrated in FIG. 4E, a portion 48 to be the bottom of the body is welded, and finally a portion to receive a bolt of a valve bonnet 10 is welded (not illustrated). After the body welding, heat treatment is performed for stress relaxation if necessary. Examples of the welding of the present embodiment can be used include tungsten insert gas (TIG) welding, metal insert gas arc (MIG) welding, metal active gas (MAG) welding, and submerged welding.

[0037] After the body welding is completed, in order to fit a gate segment part, the opposing cylindrical portions of the connection pipe 22 inserted in FIG. 4D is machined with the U-axis machining center so as to have predetermined spacing, shape, and surface roughness (not illustrated). Then, parts such as a gate 12, the bonnet 10, and a stem 6 separately produced are assembled to complete a gate valve.

SECOND EMBODIMENT

[0038] In the present invention, a weld portion of a connection pipe may be made as illustrated in FIG. 5. That is, a protrusion 57 having a ring shape is integrally formed with a connection pipe outside the connection pipe 55 in a shape forming part of a body spherical portion. A boundary between the outer circumference of the protrusion 57 and an opening fabricated so as to match the outer circumference of the protrusion 57 is included in a weld portion 53. Protruding the protrusion 57 by 2 cm or more outside the connection pipe, at radiological inspection, facilitates irradiation of the weld portion 53 with radiation 61 from a radiation source 60 and fixing, inside the body, a photosensitive film 62 for radiological inspection. As a result, the radiological inspection can be easily performed.

[0039] Although the above description has been made with reference to the embodiments, it should be understood by those skilled in the art that the present invention is not limited the embodiments and that various changes and modifications can be made within the spirit of the present invention and the scope of the attached claims.

REFERENCE SIGNS LIST

[0040] 1 STEM INDICATOR [0041] 2 STEM COVER [0042] 3 HAND WHEEL [0043] 4 YOKE NUT [0044] 5 YOKE [0045] 6 STEM [0046] 7 YOKE BOLT [0047] 8 STEM PACKING [0048] 9 RELIEF VALVE [0049] 10 BONNET [0050] 11 BONNET BOLT [0051] 12 GATE [0052] 13 SEAT RING [0053] 14 BODY [0054] 15 LEG [0055] 16 FLANGE [0056] 17, 22, 32, 45, 46, 55 CONNECTION PIPE [0057] 20, 50 BODY [0058] 30, 44 CIRCUMFERENTIAL PORTION OF SITE OF BODY AT WHICH WELDING IS PERFORMED [0059] 33, 43, 53 WELD PORTION [0060] 40, 41 BODY PORTION [0061] 42 OPENING [0062] 57 PROTRUSION [0063] 60 RADIATION SOURCE [0064] 61 RADIATION [0065] 62 FILM