JPH0335494Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an all-welded ball valve.

(Prior Art) Fully welded ball valves have become more popular in recent years than bolted ball valves due to their high reliability against external leakage, light weight, and compactness. especially,
For ball valves that handle sour gas containing a large amount of H ₂ S, CO ₂ or chlorine, external leakage is absolutely unacceptable considering environmental pollution and the impact on the human body, so naturally a fully welded type is required. .

Conventionally, as this type of all-welded ball valve, those shown in FIGS. 3 to 5 are known. That is, this ball valve has a main body 2 forming a spherical shell body 21 having openings 4 on both sides.
2 and a sub body 23, the main body 22
Seal rings 5 and 6 are mounted inside the subbody 23. A ball-shaped valve body 8 having a through hole 7 that communicates with the opening 4 and serves as a fluid flow path is rotatably supported on the main body 22 by an upper stem 9 and a lower lower stem 10. 22 and the subbody 23 are integrally connected by welding the entire circumference at the joint Y.

As shown in FIG. 4, this joint Y has a U-shaped groove formed on the outside, and protrusions 24a and 24b are provided on each root surface of the main body 22 and sub-body 23 to fit them together. It was then butt welded. Alternatively, as shown in FIG. 5, a protrusion 24c having an L-shaped cross section is provided on the back side of the U-shaped groove from the sub-body 23 side to form a space 25, and the back side of the valve body 8 is formed by burn-through during welding. In addition, Body 21
It is designed to prevent damage to the inside of the

(Problems to be solved by the invention) The welded part (including the heat-affected zone) is in an as-welded state, has a higher hardness than the base metal, and has residual stress due to welding. The absolute value of this residual stress differs depending on the implementation method, measurement method, etc., but most are 10Kg/ ^mm2 , and high ones are 40 to 50Kg/mm2.
It can be ^m2 . If such a welded state comes into contact with the sour gas, there is a very high possibility that sulfide stress corrosion cracking and chloride stress corrosion cracking will occur.

By the way, in order to prevent this stress corrosion cracking, it is effective to perform stress relief annealing on the welded portion to remove residual stress caused by welding. However, in fully welded ball valves, Teflon bearings, Teflon sheets, rubber O-rings, etc. are used as bearings and sealing members for the stem 9 and lower stem 10 near the final weld tangent, so the annealing temperature (usually 600°C Increasing the temperature of the welding part to a temperature higher than
Judging from the temperature (200℃, rubber is about 80℃), it is impossible.

In addition to stress relief annealing, there are mechanical stress relief methods such as peening that can be used to remove residual stress, but their effectiveness is not clear and they cannot be applied to fully welded ball valves due to workability. I can say that.

This idea was made in view of the problem of cutting.
The purpose of the present invention is to provide a fully welded ball valve that can withstand the use of corrosive fluids even in the welded state.

(Means for Solving the Problems) In order to solve the above problems, the present invention has a main body and a sub-body forming a spherical shell-like body with openings on both sides, and the main body has:
In the ball valve formed by rotatably housing and integrally joining a ball-shaped valve body having a through hole that communicates with the opening and communicates with the fluid flow path to form a fluid flow path, the joining by welding Department,
Welding to the area of the build-up part of the build-up part made of weld metal of a corrosion-resistant material buttered on the inner surface of the joint before welding, and the weld groove formed from the middle layer of this build-up part to the outside surface. a first welded portion made of the same type of weld metal as the built-up portion;
A dummy plate that covers the welding surface of the first welding part and is made of the same type of material as the base metal, and a dummy plate that is made of the same type of weld metal as the base metal and that is welded from the dummy plate to the base metal in the weld groove. It is formed from two welded parts.

(Example) Next, an example of the present invention will be described with reference to the drawings.

1 and 2 show a ball valve according to the present invention, and the ball valve shown in FIGS. Since they are the same, corresponding parts will be designated by the same numbers and their explanation will be omitted.

In FIG. 1, the joint X between the main body 2 and the sub-body 3 is butt welded from the outside with a U-shaped groove, as shown in FIG.

That is, a built-up part 1 made of corrosion-resistant weld metal that has been buttered to a thickness H on the inner surface of the joint part X in advance.
A U-shaped groove is formed toward the outer surface from the intermediate layer of 1a and 11b. By forming protrusions 12a and 12b on the root surface of this U-shaped groove, that is, on the end surfaces of the main body 2 side and the sub-body 3 side, respectively, of the joint where the U-shaped groove is not formed, and the two fitting into each other at the time of joining, , to prevent burn-through to the inside during welding.

Then, the welded part
A first welded part X1 welded in the range of a and 11b,
Dummy plate 1 covering the welding surface of the first welding part X1
3 and from the second welded part It has been formed. The first welding part X1 is the built-up part 11
The dummy plate 13 is made of the same type of weld metal as the base metal, and the second welded portion X2 is made of the same type of weld metal as the base metal.

The weld metal of the built-up parts 11a and 11b is made of Inconel, Stellite, Hastelloy, etc., which are difficult to cause stress corrosion cracking even in the welded state (hereinafter referred to as high SCC limit stress materials). Appropriate materials should be selected depending on the external environment, welding conditions, etc. Further, the build-up thickness H of the build-up parts 11a and 11b needs to be designed to an appropriate thickness that takes into account the amount of corrosion caused by the internal fluid of the main body 2 and sub-body 3.

If the dummy plate 13 is directly welded to the welding surface of the first welding part X1 made of the same type of weld metal as the high SCC limit stress material with a welding rod made of a different metal material such as carbon steel, cracks will occur at the limit part. In order to prevent this cracking, the welding surface of the first welded portion X1 is coated.

Therefore, since the surfaces of the dummy plate 13 and the first welded part X1 remain as unwelded parts, the existence of these unwelded parts is taken into consideration when calculating the wall thickness of the main body 2 and subbody 3, and when evaluating the strength of the main body 2 and the subbody 3, such as the presence or absence of brittle fracture. It is necessary to give sufficient consideration.

(Effects of the invention) As is clear from the above explanation, according to the invention, by providing a built-up part made of weld metal of a corrosion-resistant material on the inner surface of the final welding part of the ball valve, the final welding part is welded. Even if it comes into contact with a corrosive fluid in its original state, stress corrosion cracking will not occur, so treatments such as stress relief annealing and peening to remove residual stress and reduce hardness are not necessary.

In addition, by covering the welding part of the first layer of weld metal made of corrosion-resistant material with a dummy plate made of the same material as the base metal, welding up to the final layer of the base metal can be performed using the same type of welding rod as the base metal. This makes welding work easier, and there is no need to use expensive corrosion-resistant welding rods, leading to cost reductions.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a ball valve according to the present invention, FIG. 2 is an enlarged sectional view of section A in FIG. 1, FIG. 3 is a sectional view of a conventional ball valve, and FIG. FIG. 5 is an enlarged sectional view of section B in FIG. 3, showing another example of section B in FIG. 1... Body, 2... Main body, 3... Sub body, 4... Opening, 7... Through hole, 8...
Valve body, 11a, 11b... built-up part, 12a, 1
2b...Protrusion part, 13...Dummy plate, X1...First welding part, X2...Second welding part.

Claims (1)

[Scope of utility model registration request] The valve body has a main body forming a spherical shell-like body with openings on both sides, and a ball-shaped valve body having a through hole communicating with the opening and forming a fluid flow path in the main body is rotatable. In a ball valve formed by integrally joining the main body and sub-body by welding the entire circumference, the welded joint is made of a welded metal of a corrosion-resistant material that is buttered on the inner surface of the joint before welding. a first welded part made of the same type of weld metal as the built-up part, which is welded to the range of the built-up part of the weld groove formed from the intermediate layer of the built-up part toward the outer surface; , a dummy plate that covers the welding surface of this first welding part and is made of the same type of material as the base metal, and a welded metal of the same type as the base metal that is welded from the dummy plate to the base metal in the welding groove. A ball valve characterized in that it is formed from a second welded portion.