JPS61138109A - Measuring method of axial displacement of rotary displacement type bellows joint - Google Patents

Abstract

PURPOSE:To perform accurate monitoring by installing an axial displacement measuring sensor at the opposite side of an angular displacement restraining mechanism, installed at a specific position, across metallic fixtures fitted to two opposite shells, and measuring and converting the quantity of strain caused by variation in its tensile force into the quantity of axial displacement. CONSTITUTION:Skirts 3 and 4 at both ends of back-up and boundary bellows 1 and 2 are connected to cylindrical pipes 8 and 8': and one-terminal sides of flow sleeves 6 and 6' in the bellows 1 are fitted to ducts 7 and 7' and other-terminal sides are brought into slide contact with each other. Then, the ducts 7 and 7' are connected to the pipes 8 and 8' respectively. Further, the opposite shells 9 and 9' are connected together across a connection ring 10 so that they are rotatable with pins 11 provided in four directions at angular intervals of 90 deg.; and the sensor 14 is installed between the metallic fixtures 12 and 12' fitted opposite the shells 9 and 9' in parallel to a presser jig 13 which is provided temporarily. Then, rotary motion and axial displacement which is not expected and harmful are detected as the tensile force variation of the sensor 14, thereby evaluating respective components of rotation and axial displacement from the quantities of strain which are 180 deg. different.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring axial displacement of a rotary displacement type bead joint.・[Conventional technique W
Pipes used in nuclear power plants, such as those used in the primary cooling system of fast breeder reactors (hereinafter referred to as FBRs), carry liquid metallic sodium at temperatures as high as 500°C. Because it is transported, the material used for the piping is stainless steel or nickel alloy steel, which has high high temperature strength. However, these steel materials have a large coefficient of thermal expansion, and the thermal expansion of the piping system during continuous bombardment increases, leading to an increase in thermal stress, and the allowable stress distribution of the material also decreases in proportion to the temperature. As a result, there is a risk that the piping system will be damaged. Therefore, as a mitigation method, complicated piping is required, which results in an increase in piping length and an increase in plant construction costs. It is a factor that causes this.

``As a means to improve this increase in plant construction costs, a bellows joint was installed at the M position of the piping system to absorb thermal expansion and make the piping system more compact.'' □However, in the -1 atom cover, it is necessary to prevent the leakage of radioactivity outside the system, so even if the bellows part that forms the boundary against external leakage of the internal fluid is damaged, Various measures must be taken to ensure that plant safety is not compromised. A rotary displacement type bellows joint, which is often used in FBR, is configured to allow only rotational deformation and restrict axial displacement. However, due to the manufacturing tolerances of the bellows joint and the possibility of deformation due to loads during operation, it is impossible to assume that there will be no shaft displacement. Moreover, since the displacement is a movement different from the permissible displacement, an increase in the displacement position has a harmful effect on the bellows portion, creating the risk of shortening the life of the bellows. Therefore, in order to maintain plant safety, it is absolutely necessary to measure such displacement, detect the danger in advance so that the health of the plant is not compromised, and prevent piping system damage accidents. It's becoming.

[Aspects of the Invention] The present invention was made in view of these technical problems, and aims to provide a method for measuring shaft displacement, thereby providing accurate monitoring during installation and operation. It is something to do.

[Structure of the Invention] The method for measuring angular displacement of a rotary displacement type bellows joint of the present invention includes:
The axial displacement measurement sensor was installed via the pin structure installed on the opposing shells of the rotary displacement type bellows joint and the angular displacement restraint mechanism installed at the 90' rotated position via the metal fittings attached to the two opposing shells. The method is characterized in that the amount of strain due to a change in tension is measured, and the amount of strain is converted into an amount of axial displacement for measurement.

[Example] A method for measuring shaft displacement of a rotary displacement type bellows joint of the present invention will be described in detail. First, the configuration for carrying out water spraying will be explained with reference to the drawings. 1 is the backup bellows,
2 is arranged concentrically on the outside of the backup bellows.
With the boundary bellows, these bells 1.2
A skirt 3.4 is connected to both ends of. 6.6' is a narrow sleeve installed inside the backup bellows 1, the 1 end of which is attached to the duct 7.7' so that it becomes one body, and the other end is in sliding contact with each other. It serves to reduce thermal overstress caused by the fluid within the bellows.

Also, boundary bellows 2 and backup bellows 1
The skirt 3.4 is connected to both ends of the duct 7.7', and the duct 7.7' is connected to each of the circular pipes 8, 8' which are connected to the skirt 3.4 at both ends of the boundary bellows 1, the skirt 3. 4. The cylindrical tube 8.8' and the duct 7.7' form part of the boundary of the bellows joint. They are rotatably connected by pins 11 provided in four angular directions. 12.12' is a metal fitting for attaching a sensor for measuring shaft displacement, and is attached opposite to the shells 9, 9'. Metal fittings 12.
12' is a sensor 14 for measuring axial displacement.
is installed in parallel with the temporary holding jig 13.

Next, a method for measuring shaft displacement in the rotary displacement type bellows configured as described above will be explained. In a gimbal type bellows joint that only allows rotational displacement, during operation, the bending load is applied due to the thermal expansion of the piping, and the pins 11, which are installed at four equal intervals in the circumferential direction, are bent together with the shells 9 and 9'. Rotate. This rotational movement and unexpected harmful axial displacement appears as a change in tension on the axial displacement measuring sensor 14 installed on the metal fitting 12, 12', and the amount of strain due to the change in tension is measured. The rotational displacement component and the axial displacement component are evaluated from the strain amounts measured 180 degrees apart.

[Effects of the Invention] As detailed above, in the shaft displacement measuring method of the present invention, the shaft displacement is accurately measured by the shaft displacement measuring sensor installed through the fitting when the sensors are mounted on two opposing shells. Therefore, even if an abnormal load is applied due to flow vibration of the heat medium flowing in the pipe, sudden change in pressure, etc., it is possible to easily and quickly detect whether excessive displacement has occurred in the bellows joint, and to check if a part of the boundary of the bellows joint has occurred. This has an extremely large effect on improving reliability, as it makes it possible to prevent damage to the plant, thereby increasing the safety of the entire plant.

[Brief explanation of the drawing]

The figure shows a rotary displacement bellows joint that implements the shaft displacement measurement method according to the present invention! FIG.

Claims (1)

[Claims] Axial displacement measurement installed via metal fittings attached to two opposing shells on the opposite side of a pin structure and an angular displacement restraint mechanism installed at a position rotated by 90 degrees in a rotary displacement type bellows joint. A method for measuring axial displacement of a rotational displacement type bellows joint, characterized in that the amount of strain due to a change in tension of a sensor is measured, and the amount of strain is converted into an amount of axial displacement.