JP2000074217A - Welded metal bellows - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve stress concentrating to the root part of a welded part so as to prolong the use life thereof. SOLUTION: Two thin plates 3, are joined together so as to form a bellows plate 2. A plurality of bellows plates 2 are line up in a row, and two adjacent bellows plates are connected by welding between their inner diameter parts and between their outer diameter parts, alternately. Thus formed welded metal bellows 1 are set in a mechanical seal or the like which is fitted in a rotary part or the like in an aircraft engine. With this arrangement, the welded metal bellows 1 serve as a bellows seal for sealing at that part. With the bellows plates 2 each composed of the two thin plates 3, 4, stress concentrating to the root part 6 of the welded part 5 can be relieved, thereby it is possible to greatly prolong the use life in a designed use range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded metal bellows, and more particularly to a welded metal bellows effective as a bellows seal such as a mechanical seal used under severe conditions such as high speed, high temperature and cryogenic temperature.

[0002]

2. Description of the Related Art As bellows seals such as mechanical seals used under severe conditions such as high speed, high temperature and cryogenic temperature such as nuclear power plants and aircraft engines, welding as shown in FIG. A metal bellows 11 is used.

[0003] That is, this weld metal bellows 11
A plurality of metal bellows plates 12 formed in a corrugated ring by punching or the like are arranged in a line, and between the inner diameter portions and the outer diameter portions of the adjacent bellows plates 12 and 12 are alternately connected by welding, and the whole is bellows. The retainer 18 is connected to the bellows plate 12 at one end by welding, and the bellows plate 12 at the other end is formed.
Is connected to the adapter 19 by welding.

Then, the weld metal bellows 11 constructed as described above is attached to a predetermined position of a mechanical seal, for example, and the mechanical seal is attached to a rotating part of a nuclear power plant or an aircraft engine.
Numeral 1 functions as a bellows seal, which can seal a rotating part of a nuclear power plant or an aircraft engine used at high speed, high temperature, and extremely low temperature.

[0005] However, in the case of the welded metal bellows 11 having the above-described structure, when evaluating the characteristics and the life within the design specification range, the target actual product is manufactured and the characteristics,
Since the life was evaluated, enormous cost and time were spent in developing one product.

Further, in the welded metal bellows 11 having the above-described structure, a stress is structurally applied to the base 16 of the welded portion 15 of the bellows plate 12 (a boundary portion between the welded portion 15 and the non-welded portion). Is concentrated, so that the stress concentrated on the portion can be relaxed to extend the life within the design range. However, no effective means for relaxing the stress concentrated on the portion has been found.

The present invention solves the above-mentioned problems of the prior art, and can easily evaluate the characteristics and life within the design specification range. It is an object of the present invention to provide a weld metal bellows that can be developed in a short time.
Another object of the present invention is to provide a welded metal bellows having a structure capable of relieving stress concentrated at the root portion of a welded portion of a bellows plate, thereby greatly extending a service life within a design use range. Is what you do.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to arrange a plurality of corrugated annular metal bellows plates in a line so that the bellows plates can be arranged between the inner diameter portions of adjacent bellows plates and outside. Welding metal bellows in which the diameter portions are alternately connected by welding to form a bellows tube as a whole, wherein the bellows plate is formed by laminating two thin plates having different plate thicknesses. It was done. Also, of the two thin plates of the bellows plate,
A means is adopted in which the thinner plate is positioned on the pressure receiving side and the thicker plate is positioned on the backup side.

[0009]

According to the present invention, a bellows plate is constructed by laminating two corrugated annular thin plates having different plate thicknesses by employing the above-described means, and receives the thinner one of the two thin plates. By locating the pressure side and the thicker side on the backup side, stress concentrated on the root of the welded portion of the bellows plate can be reduced.

[0010]

Embodiments of the present invention shown in the drawings will be described below. FIG. 1 shows an embodiment of a welded metal bellows according to the present invention. This welded metal bellows 1 is used in a high-speed, high-temperature, extremely low-temperature, etc., such as a nuclear power plant or an aircraft engine. It is used as a bellows seal or the like of a mechanical seal used under conditions, and a plurality of metal bellows plates 2 are arranged in a line, and between the inner diameter portion and the outer diameter portion of adjacent bellows plates 2, 2. Are alternately connected by gas welding or the like to form an entire bellows cylinder.

The bellows plate 2 is formed by laminating two thin plates 3 and 4 having the same size and shape but different thicknesses, which are formed in a corrugated ring by punching or the like. 4 is stainless steel, titanium, Monel,
It is formed from a weldable metal such as Inconel.

Of the two thin plates 3 and 4 of the bellows plate 2, the thin one 3 is located on the pressure receiving side, and the thick one 4 is located on the backup side. Therefore, for example, when the outer peripheral side of the weld metal bellows 1 is the pressure receiving side and the inner peripheral side is the backup side, the thinner thin plate 3 is located on the outer peripheral side, and the thicker thin plate 4 is located on the inner peripheral side. Will be located.

At least one of the pressure receiving side thin plate 3 and the backup side thin plate 4 is provided with a plurality of through holes (not shown) communicating with the counterpart thin plates 4 and 3. 2 improves the responsiveness.

A retainer 8 is connected to the bellows plate 2 at one end by gas welding or the like, and an adapter 9 is connected to the bellows plate 2 at the other end by gas welding or the like, and is mechanically connected via the retainer 8 and the adapter 9. It is designed to be attached to a predetermined position of a device such as a seal.

When the welded metal bellows 1 constructed as described above is attached to a predetermined position of a mechanical seal, for example, and the mechanical seal is attached to a rotating part of a nuclear power plant or an aircraft engine, the welded metal bellows 1 is attached. By functioning as a bellows seal, a rotating part of a nuclear power plant or an aircraft engine can be sealed.

The present inventors evaluated the life of the weld metal bellows 1 according to this embodiment and the conventional weld metal bellows 11 by using the finite element method (finite element method).
The stress analysis of the welded parts 5 and 15 of the bellows plates 2 and 12 was performed by element method. The results are shown in FIGS.

Here, FIG. 3 shows the result of stress analysis of the welded portion of the bellows plate of the welded metal bellows according to this embodiment, and FIG. 4 shows the details of the welding root portion serving as a fracture starting point in FIG. FIG. 5 shows a result of stress analysis of a welded portion of a bellows plate of a conventional weld metal bellows, and FIG.
FIG. 7 shows details of a weld root portion serving as a fracture starting point in FIG. 5, and FIG. 7 shows the "pressing pressure of the weld metal bellows according to this embodiment and the conventional weld metal bellows and acts on the root portion of the weld portion of the bellows plate. Relationship with MISES stress ". FIG. 7 (〇) shows the weld metal bellows 1 according to this embodiment, and FIG. 7 (△) shows the conventional weld metal bellows 11.

According to the result of this analysis, stress was concentrated on the root 16 of the welded portion 15 of the bellows plate 12 in the conventional weld metal bellows 11, but in the bellows plate 1 in the weld metal bellows 1 according to this embodiment. It can be seen that the stress concentrated on the base 6 of the welded portion 5 of No. 2 is reduced.

It is extremely difficult to experimentally determine the stress value acting on the roots 6 and 16 of the weld. Therefore, the inventors of the present application conducted a "test for examining the life of the bellows plate under pressure" in order to confirm that the result of the stress analysis by the finite element method was correct. Pressure 0.01-0.1kg
When a variation of f / mm ² was given, as a result, a remarkable improvement in the life characteristics of the product of the present invention was recognized. FIG. 8 shows the results of this test. In the figure, the horizontal axis represents MI obtained by the above-described analysis.
The SES stress (pressurized 0.1 kgf / mm ² ) and the vertical axis indicates the number of lifetimes obtained by this test. Here, (〇) shows the weld metal bellows 1 according to this embodiment, and (△) shows the conventional weld metal bellows 11.

In general, it is known that when the modified Goodman diagram is taken into consideration, a decrease in stress amplitude improves the life characteristics. From these evaluation results, it can be seen that the weld metal bellows 1 according to this embodiment has a smaller stress acting on the root 6 of the welded portion 5 with respect to the applied pressure than the conventional weld metal bellows 11. Was confirmed. Further, the weld metal bellows 1 according to this embodiment
It was confirmed that the stress concentrated on the base 6 of the welded portion 5 of the bellows plate 2 was reduced. Therefore, it was experimentally confirmed that the result of the stress analysis by the finite element method was correct.

In the welded metal bellows 1 according to this embodiment configured as described above, when evaluating the characteristics and the life prediction within the design specification range, they are evaluated by the stress analysis by the finite element method. Therefore, unlike the conventional one, there is no need to prepare and evaluate a target product, and one product can be developed at a low cost and in a short time.

Further, the bellows plate 2 is composed of two thin plates 3 and 4, the thinner thin plate 3 is located on the pressure receiving side, and the thicker thin plate 4 is located on the backup side. , Base 6 of welded portion 5 of bellows plate 2
The stress concentrated on (the boundary between the welded portion 5 and the non-welded portion) can be reduced. Therefore, the life within the design specification range can be significantly extended as compared with the conventional one.

[0023]

According to the present invention, as described above, the bellows plate is formed by laminating two thin plates having different plate thicknesses, so that the root portion of the welded portion of the bellows plate (between the welded portion and the non-welded portion) is formed. The stress concentrated on the boundary can be reduced. Therefore, an excellent effect is obtained such that the life within the design specification range can be greatly extended as compared with the conventional one in which the bellows plate is formed of one thin plate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a weld metal bellows according to the present invention.

FIG. 2 is a schematic sectional view showing an example of a conventional weld metal bellows.

FIG. 3 shows a pressurization of a welded portion of a bellows plate of a welded metal bellows according to the present invention by a finite element method of 0.1 kgf /
FIG. 4 is an explanatory diagram showing the results of stress analysis at mm ² .

FIG. 4 is an explanatory diagram showing details of a welding root part (C part) in FIG. 3;

FIG. 5 is an explanatory diagram showing a result of stress analysis at a pressurization of 0.1 kgf / mm ² by a finite element method on a welded portion of a bellows plate of a conventional weld metal bellows.

FIG. 6 is an explanatory diagram showing details of a welding root portion (D portion) in FIG. 5;

FIG. 7 is an explanatory diagram showing “the relationship between the applied pressure and the MISES stress acting on the root of the welded portion of the bellows plate” of the weld metal bellows according to the present invention and the conventional weld metal bellows.

FIG. 8 is an explanatory diagram showing “relationship between MISES stress acting on the root of the welded portion of the bellows plate when pressurized and life” of the weld metal bellows according to the present invention and the conventional weld metal bellows.

[Explanation of symbols]

 1, 11 ... welded metal bellows 2, 12 ... bellows plate 3, 4, ... thin plate 5, 15 ... welded part 6, 16 ... root part 8, 18 ... retainer 9, 19 ... adapter

Claims (2)

[Claims] 1. A plurality of corrugated annular metal bellows plates are arranged in a line, and the inner and outer diameter portions of adjacent bellows plates are alternately connected by welding to form an entire bellows tube. A weld metal bellows formed, wherein the bellows plate is formed by laminating two thin plates having different plate thicknesses. 2. The weld metal bellows according to claim 1, wherein, of the two thin plates of the bellows plate, a thinner plate is located on the pressure receiving side and a thicker one is located on the backup side.