JPS6056952B2 - Seal mechanism of low temperature flange - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sealing mechanism for various flange joints such as low-temperature valve flanges and piping flanges.

[Conventional technology]

Many types of flange joints are used in industrial equipment and devices such as chemical plants.

When selecting these, consider the operating temperature, operating pressure,
It is necessary to consider the chemical and physical properties of the fluid to be handled, the severity of use and service life, the difficulty of construction and maintenance, etc. In recent years, the number of devices that handle low-temperature liquefied gas fluids such as LPG, LNG), liquid oxygen, liquid nitrogen, liquid air, and Freon has been increasing, but many of the flange joints in these devices are gaskets that have been commonly used. However, this has caused fluid leakage, which has become a problem. For example, a flange joint as shown in FIG. 1 was used. That is, the gasket 3 was inserted between the joint surfaces 7, 7 of both flanges 1, 1, and the flanges 1, 1 were tightened with double bolts 2 and nuts 2'', 2''. In this case, in order to improve the effect of the gasket, it is necessary to tighten the plurality of bolts 2 while controlling the torque so that each bolt is tightened uniformly, and it is necessary to control the tightening method. Furthermore, if quality control of the gasket or the gasket surface of the flange is insufficient, there is a possibility that fluid leakage may occur even if bolt tightening is controlled. Furthermore, when handling high-temperature fluids, it is easy to obtain a tighter seal due to the thermal expansion of the base material even if the above-mentioned controls are insufficient, whereas in the case of low-temperature fluids, the opposite is true. Shrinkage occurs, and even if the product is sufficiently sealed during installation, leakage may occur on the other side, and a technical solution has been desired.
In particular, when handling cryogenic fluids such as LNG that are below -40°C, the temperature of the flange joint itself drops to a low temperature, but if there is a sudden drop in the process of dropping, a temperature difference occurs in the circumferential direction of the flange. The flange may become deformed or
Excessive force acts on the gasket, damaging the gasket and causing fluid leakage.

Further, even if the flange joint is carefully and gradually temperature-cured, the difference in the coefficient of thermal expansion of the flange 1, bolt 2, and gasket 3 may result in incomplete sealing at low temperatures, which may result in fluid leakage. In order to prevent this, it is extremely difficult to select the materials for each member. On the other hand, in joints using these gaskets, if the sealing by the gasket becomes incomplete during use and fluid leakage occurs, the outer periphery 4 of the joint surface of the flanges 1, 1 is seal-welded as shown in Fig. 2a. A method has also been proposed.

In this case, since the gasket 3 is embedded in the joint end face as shown in the figure, the low-temperature liquefied gas that has passed through the layer with the gasket 3 on the joint surface and entered between each joint surface on the outside in the thickness direction remains as it is. As the temperature rises,
These liquefied gases may vaporize and increase the pressure in this area, potentially damaging the weld. Further, as shown in FIG. 2B, a sealing material 5 is used at the joint where the gasket 3 is inserted, and the joint is sealed by a seal weld 6. In this case as well, the seal means is designed to prevent fluid leakage, and there are problems similar to those shown in FIG. 2a. As a means for solving the above-mentioned problem, the method shown in FIG. 3 has been conventionally implemented.

In FIG. 3, small-diameter disks 14, 14 are formed integrally with the flange body, and holes with a diameter smaller than the diameter of the flange 11 and the same diameter as the flange inner diameter are bored on the joint surfaces of the joint flanges 11, 11, respectively. will be installed respectively.

Both flanges are axially tightened by bolts 12 and nuts 12''.

It is generally desirable that this tightening force be stronger than the conventional tightening force. After the joining operation is completed, the outer periphery 15 of the joint portion of the small diameter discs 14, 14 is completely sealed by seal welding. Even with the method shown in FIG. 3, a fairly good seal can be obtained without using a gasket, but in this case, the flange on which the small disk 14 is formed has a complicated shape and is expensive, and the material of the small disk is inferior. It tends to be uniform.

It may also be necessary to use dissimilar materials at the flange joints to provide a more complete seal. [Problems to be solved by the invention] The inventor has conducted various research and prototypes to solve the various problems of the flange sealing mechanism at low temperatures as described above, and has solved these problems. We have developed a highly effective sealing method that solves the problem and prevents leakage.

That is, the present invention provides a low-temperature sealing mechanism that can achieve a more complete seal without using expensive flanges made of non-uniform materials and by using different materials for the joints.

[Means for solving problems]

That is, the present invention solves the above-mentioned problem, and its means include, in a sealing mechanism for the joint surface of a joint flange for low temperature use, a sealing mechanism for the joint surface of each joint flange to be joined, which is separately formed at the end of the joint surface of the joint flange to be joined. At each end, one or more small-diameter disks are provided with a hole having an outer diameter smaller than the outer diameter of the joint surface of the flange and larger than the outer diameter of the joint surface of the flange, and having a hole equal to the inner diameter of the center hole of the joint flange. The outer end surfaces of the small-diameter disks are brought into close contact with each other through metal contact, and each of the joint flanges is axially tightened by bolt means, and the outermost surface of the small-diameter disks arranged and connected to each end of A low-temperature method characterized by welding the outer periphery of the closely joined surfaces of the ends, and sealing the joint surfaces between the flange and the small-diameter disk, and between the small-diameter disks and the small-diameter disk by alternately welding the outer periphery and the inner periphery. This is the sealing mechanism for the flange.

〔Example〕

FIG. 4 is an explanatory sectional view of one embodiment of the present invention, in which the perforated small-diameter disks 24, 24 are manufactured separately from the flanges 21, 21, respectively.

The outer diameter of the small-diameter disks 24, 24 is smaller than the outer diameter of the flanges 21, 21, and larger than the outer diameter of the joint surface of the flanges 21, 21, and the holes of the small-diameter disks 24, 24 are formed in the flanges 21, 21. 21 is formed to have the same diameter as the inner diameter. An end surface 28 of a small-diameter circular plate 24 with holes is brought into close contact with the joint surface of each flange 21, and the inner periphery 27 of this contact surface is joined by welding.
After the flange 21 and the small-diameter disc 24 are connected in this manner, the flange joint brings the end surfaces 26 of each of the small-diameter discs 24, 24 into close contact and is firmly tightened with bolts. The contact surfaces 28 and 26 are machine finished. After joining, the outer periphery 25 of the joint portion of the small diameter discs 24, 24 is sealed by welding. In this embodiment, there is one small-diameter disk in close contact with the flange, but there may be more than one, and the number does not have to be the same on the left and right, and the outer periphery of the outermost end is finally welded. Further, the flange 21 and the small diameter disc 24 may be made of the same material, but they may also be made of different materials if necessary. FIG. 5 is an explanatory cross-section of another embodiment of the present invention,
In this embodiment, each flange 31 has two pairs of perforated small-diameter disks 34, 34a on close contact surfaces 38, 3.
Closely connected at 8a.

The flange 31 and the small-diameter disk 34 are welded together at the outer periphery 37, and the small-diameter disks 34 and 34a are welded at the inner surface 37a. At the joint surface 36 of the small diameter disk 34a, the outer peripheral portion 35
is welded. As described above, in the embodiments shown in FIGS. 4 and 5, seal welding is performed alternately on the inner and outer circumferences. In the embodiment shown in FIG. 5, the number of pairs of small-diameter disks is the same on the left and right, but it is not necessarily necessary that the number is the same on the left and right, and a different number of pairs of small-diameter disks on the left and right may be used depending on the situation. [Effects of the Invention] Since the flange sealing mechanism of the present invention does not use a gasket, it is desirable to perform torque control on each bolt as usual when tightening bolts. Even without controlled tightening, metal-to-metal contact provides a reliable connection without tightening, and welding provides a complete seal.

Moreover, it is of course unnecessary to control the quality of the gasket.
Furthermore, even in the case of a sudden temperature drop, since no gasket is used, failures due to thermal shock or seal failures due to differences in expansion coefficients are eliminated. Furthermore, since the outer periphery of the joint surface is sealed and welded, even if fluid enters the joint, it will not leak to the outside.

It is also possible to improve the adhesion by changing the material of the small diameter disc and utilizing the difference in expansion coefficient.

In addition, since stress is concentrated on the welded part, which is a fixed part, we provide seal welds alternately on the inside and outside, and by dispersing the stress effect over the entire small diameter disc, we have flexibility in the tightened state and localize it to the small diameter disc. to avoid extreme stress. be able to. Furthermore, if excessive stress is applied to the small diameter disc in the axial direction due to tightening, etc.
The stress can also be distributed by increasing the number of small-diameter disks or pairs of small-diameter disks.

As mentioned above, this joint seal is used for valves and piping that handle low-temperature fluids, and experience shows that it is particularly effective for fluids generally at -40°C or lower.

[Brief explanation of the drawing]

Fig. 1 is an explanatory sectional view of an example of a conventional flange seal mechanism, Fig. 2 A and b are illustrative sectional views of an example of another conventional flange 7 seal mechanism, and Fig. 3 is an explanatory sectional view of an example of another conventional flange seal mechanism. FIG. 4 and FIG. 5 are explanatory cross-sectional views of embodiments of the sealing mechanism of the present invention. 11, 21, 31...flange, 14, 24,
34, 34a... Perforated small hole disc, 7, 16, 2
6, 36... joint surface, 15, 25, 35...
...The outer periphery of the joint surface.

Claims (1)

[Scope of Claims] 1. In a sealing mechanism for a joining surface of a joint flange for low temperature use, the outer diameter of the joint flange is smaller than the outside diameter of the joint flange and is separately formed at the end of the joining surface of each joint flange to be joined. One or more small-diameter disks having an outer diameter larger than the outer diameter of the joint surface and having a hole equal to the inner diameter of the center hole of the joint flange are arranged and coupled at each end, and the small-diameter The outer end surfaces of the disks are brought into close contact with each other by metal surface contact,
Each of the joint flanges is tightened in the axial direction by bolt means, and the outer peripheries of the close joint surfaces of the outermost ends of the small diameter discs arranged and coupled to each end are welded, and the flange and the small diameter disc are connected to each other, and The joint surface between the small diameter disc and the small diameter disc is the outer periphery,
A low-temperature flange sealing mechanism characterized by alternately welding and sealing the inner circumference. 2. The low temperature flange sealing mechanism according to claim 1, wherein each of the small diameter discs is formed in a plurality of pairs. 3. The low-temperature flange sealing mechanism according to claim 1, wherein the number of small-diameter disks arranged and coupled to the end of the joint surface of each flange is different from each other. 4. The low-temperature flange sealing mechanism according to claim 2, wherein the number of pairs of small-diameter disks arranged and coupled to the end of the joint surface of each flange is different from each other. 5. A sealing mechanism for a low-temperature flange according to any one of claims 1 to 4, wherein the flange and the small-diameter disk are made of different materials.