JPS61211588A - Seal mechanism of flange - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a flange sealing mechanism, particularly to a complete sealing mechanism for a piping flange for hazardous fluids.

[Prior art]

Various types of flange joints are used in various types of factory equipment such as chemical plants. Particularly in recent years, the number of devices that handle various fluids such as flammable hydrogen gas, low-temperature liquefied gases such as LPG, LNG, liquid air, liquid oxygen, and liquid nitrogen, or toxic substances such as chlorine and ammonia has increased. death,
The development of a flange joint with a complete sealing mechanism is strongly desired.

Conventionally, mechanisms using lip seal flanges or flanges with gaskets have been applied for such purposes, but these have not yet been satisfactory. A sealing mechanism using a lip seal flange is a sealing mechanism in which the joint outer surface of the flange is partially raised and that portion is welded to prevent stress from being applied to the welded portion. In the case of this seal mechanism, fluid leakage can be completely prevented, but as shown in FIG. 6, there are problems in that the shape of the lip portion is complicated and the cost is high. Furthermore, in the case of a lip seal mechanism, defects such as microshrinkage may remain in the lip part during the manufacturing and casting process, and if these defects occur continuously, if the flange is used, fluid may leak. There is a risk of Therefore, in order to maintain a perfect seal over a long period of time, strict inspection is required after the flange is manufactured, and at the same time, strict repairs must be made to areas where defects such as microshrinkage exist. In addition, when the material of the lip seal flange is carbon steel, corrosion of the seal weld becomes a problem, and corrosion prevention is an important point. It had become a big problem. Particularly in areas exposed to corrosive atmospheres, such as coastlines, thermal spraying of anticorrosive metals is sometimes used, but this work is considered to be extremely difficult.

In addition, although various improvements have been made in the shape of the joint surfaces of sealing mechanisms using flanges that use gaskets, in each case, there are drawbacks such as gaps occurring during use and leakage due to gasket deterioration. However, the complete seal was not satisfactory.

〔the purpose〕

The present invention aims to improve the shortcomings seen in the conventional flange seal mechanism described above, and in particular, to solve the above problems seen in the lip seal flange while maintaining the complete sealing performance of the lip seal flange. With the goal.

〔composition〕

According to the present invention, in a sealing mechanism using a flange joint, the outer periphery of the joint surface of each joint flange to be joined is flat-processed into a gasket surface shape, brought into close contact with each other by metal contact, and shafted by bolt means. Provided is a flange sealing mechanism characterized in that the flange is tightened in the direction of the flange and the outer periphery of the joint surface is sealed by welding.

Generally, when the joint surfaces of flanges are brought together, manufacturing errors occur in flanges obtained through normal manufacturing, and minute gaps are created in the joint surfaces due to finishing methods. for example,
As shown in FIG. 5, in the worst case, only the inner peripheral edge portions touch, and the gap widens toward the outer peripheral edge. For this reason.

If the outer circumference of a conventional flange is welded to fit the sound, stress will be concentrated at the welded part due to the tightening and removal of bolts, and there is a high possibility that cracks will occur at the welded part, making it impossible to achieve a complete seal. It can happen. Also,
If the contact surface is wide, an excessive compressive load is applied when tightening the bolt, and a tensile load due to the rebound of the contact surface when the bolt is removed is applied to the welded part, and cracks may occur in the welded part due to repeated repetition. Furthermore, it is not practical to precisely finish the entire joint surface due to high costs.

Therefore, the flange seal mechanism of the present invention is characterized in that only the outer peripheral edge of the joint surface of the flange joint used is flattened into a gasket surface shape. FIG. 1 shows a side sectional view of the joint surface of the flange joint used in the present invention,
Figure 2 shows its front view. Figure 2 shows arrow A- in Figure 1.
It is a partial front view seen from the A direction.

In FIGS. 1 and 2, the joint surfaces of the flange joint 1 include a flat outer peripheral edge 2 and a non-flat inner center 3.
The outer peripheral edge is flat-processed, and its surface roughness can be as long as that of a gasket surface, and is generally about ±0.05.
It is maintained within mm. In addition.

The gasket surface shape here refers to flat metal gaskets,
This refers to the same finished surface as that applied to gaskets intended to achieve pressure resistance and airtightness through metal contact, such as ring joint gaskets. In the case of the present invention, the ratio of the outer peripheral edge 2 and the inner core 3 of the joint surface may be such that the surface pressure of the joint surface is greater than or equal to (internal pressure x gasket coefficient) in the pipe in which it is used. The rate of tightening with bolts varies depending on usage conditions such as strength, and cannot be determined unambiguously. Therefore, it can be selected as appropriate depending on the usage conditions.1For example, in the case of LPG piping,
Usually, the ratio of the distance mΩ-1 to 2-2 (Ω-17Q-2) is 1/1.8 to 115.4. In one drawing, 5 indicates a bolt hole, and 4 indicates a fluid passage. A flange having a joint surface of such a shape can be made by bringing the joint surfaces into close contact with each other through metal contact, tightening them in the axial direction with bolts, and sealing the outer periphery of the flange joint surface by welding to achieve the desired sealing machine end. can be obtained. In this case, when welding, first tighten the flange using bolts according to the usage conditions, then partially remove the bolts at the location to be welded, and then tighten the bolts again, sequentially tightening the bolts on all joint surfaces. It is best to repeat the process around the outer circumference of the area. By doing so, the stress applied to the weld under the conditions of use can be minimized. In Figure 3,
An explanatory cross-sectional view of a sealing mechanism of an example of the flange joint of the present invention is shown.

In FIG. 3, 6 is a bolt and 7 is a weld seal portion. Further, 2' is a contact portion of the outer peripheral edge portion 2 that is in complete surface contact, and 3′ is a gap portion formed between the inner core portions 3 that are in incomplete contact. FIG. 4 shows a side sectional view of another example of the flange joint of the present invention. The flange shown in FIG. 4 is a valve bonnet flange, and the outer peripheral edge 2 of the joint surface of one of the pair of flanges (a) is formed in a convex shape for centering.
The joint surface of the other flange (b) is correspondingly formed in a concave shape. In FIG. 4, 2' is a contact portion of the outer peripheral edge 2 that is in complete surface contact, and 3' is a gap formed between the inner core portions 3 that are in incomplete contact.

In the flange used in the present invention, as described above, the joint surface is formed at the flattened outer peripheral edge 2 and the unflattened inner core 3, and the flattened outer peripheral edge 2 is formed by the gasket. It is a gasket surface that acts as a surface, and when the flanges are brought close together as shown in Figure 3,
Each flange is in complete surface contact at its outer peripheral edge 2. On the other hand, as shown in FIGS. 3 and 4, the unplanar inner core portion 3 does not come into complete surface contact, but creates a gap 3'. The gap of this gap 3' is usually such that complete surface contact of the outer peripheral edge 2 can be achieved and that it does not affect the strength of the flange.

It is about 0.5 to lom.

The flange of the present invention can be created as follows.

(1) First, the joint surface of the flange is adjusted so that the desired joint cross section is obtained, for example, the side cross section shown in Fig. 3 (line flange) or Fig. 4 (valve bonnet flange) is obtained. Rough cutting. In this case, in the line flange shown in FIG. 3, the outer peripheral edge 2 is made to form a more convex surface than the inner core 3. Also, in the valve bonnet flange shown in Fig. 4.

For centering, the joint surface of one flange (a) is made such that the outer peripheral edge 2 forms a more convex surface than the inner surface 3.

The other flange (b) has a joint surface so that the outer peripheral edge 2 forms a more concave surface than the inner surface 3 correspondingly.

(2) The outer peripheral edge 2 obtained above is flattened into a gasket surface shape.

[Effects] The flange seal mechanism of the present invention has the above configuration, and the outer peripheral edge 2 of the flange joint surface is flattened,
Since it acts as a gasket, the mutual contact at the outer peripheral edge 2 is complete.

Further, even if the joint area is reduced, the residual surface pressure value becomes equal to or higher than (internal pressure in the pipe x gasket coefficient), so a perfect seal can be obtained. Moreover, in the case of the present invention, since the outer periphery of the flange joint surface is sealed by welding,
The fluid seal is complete, and internal fluid will never leak out from the joint surface. Therefore, although the sealing mechanism of the present invention does not have a lip portion, it can seal completely like a conventional lip flange seal, and furthermore, the structure is simple and inspection is easy. However, the cost is low, and defects such as micro-shrinkage, which was a problem in the casting process of manufacturing lip flanges, occur continuously and there is almost no possibility of penetrating the seal, making it extremely difficult to manufacture from an industrial perspective. It is both effective and safe, making it extremely useful. Furthermore, unlike gasket flanges obtained by conventional methods, when the flange is tightened in the axial direction by bolt means, the stress is applied to the outer peripheral edge 2 of the flange joint surface.
This ensures that the surface pressure is maintained.

In addition, the reduced contact area reduces the tensile load due to the rebound of the contact surface, and also reduces the compressive load, which reduces the repeated load on the welded part due to bolt tightening and removal, which can lead to cracks in the weld seal. There are no such problems.

Furthermore, since the flange according to the present invention has a simple structure, corrosion protection of the welded portion can be easily performed.

The flange seal mechanism of the present invention is applicable to complete sealing of flange portions of pipes that conduct low-temperature fluids such as LPG, LNG, liquid air, liquid oxygen, and liquid nitrogen, as well as for gases that are prone to leakage such as hydrogen gas, It can be applied to complete sealing of piping flanges that conduct toxic fluids such as chlorine and ammonia.

〔Example〕

A simulated test material having a seal portion equivalent to the flange according to the present invention is subjected to a repeated compression test, which is more severe than a destructive test that assumes the pressure generated by the pulsation of a pump, etc. repeat 2
I went there 0 times. The results showed that there were no defects such as cracks in the welded area.

Further, when welding the flanges of the present invention, welding defects were caused by intentionally adding tungsten, etc., and the above-mentioned destructive test by opening and tightening the bolts was conducted in the same manner. In this case as well, there was no development of secondary defects from weld defects.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of the line flange joint surface. FIG. 2 shows its front view. FIG. 3 shows an explanatory sectional view of a seal mechanism formed using the line flange. FIG. 4 shows a side sectional view of the valve bonnet flange. FIG. 5 shows an explanatory diagram of a joint cross section of a conventional line flange. FIG. 6 shows a cross-sectional view of a conventional lip seal flange. 1...Flange, 2...Flange joint outer peripheral edge, 3
...Inner part of flange joint, 4...Fluid passage, 5...
- Bolt hole, 6... Bolt, 7... Weld seal part. Applicant's representative Patent attorney Toshiaki Ikeura Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) In a seal mechanism using a flange joint, the outer peripheral edge of the joint surface of each joint flange to be joined is flattened into a gasket shape, brought into close contact with each other by metal contact, and tightened in the axial direction by bolt means. , and a flange sealing mechanism characterized in that the outer periphery of the joint surface is sealed by welding.