Flitch plate for repairing lap weld of bottom plate of refueling water tank

Abstract

The utility model discloses a flitch for reloading water tank bottom plate lap weld repair, relates to the technical field of nuclear power welding maintenance, and is used for solving the problem that the existing reloading water tank bottom plate lap weld defect repair cannot inhibit the continuous expansion of stress corrosion cracks. The length and the width of the flitch are not less than 150mm, and the thickness of the flitch is consistent with that of the upper plate of the bottom plate of the refueling water tank; the bent upper part of the flitch is attached to the water tank bottom plate upper plate, the bent connecting part of the flitch is attached to the lap welding seam, the bent lower part of the flitch is attached to the water tank bottom plate lower plate, and the bent connecting part of the flitch can be attached to the lap welding seam and wraps the lap welding seam by changing the bending angle between the bent connecting part and the bent upper part and the bending angle between the bent connecting part and the bent lower part; and when the flitch is positioned, the crack of the lap weld is coated at the middle position of the bending connection part of the flitch in the length direction. By using the flitch, the purpose of inhibiting continuous expansion of stress corrosion cracks can be achieved, and the repair reliability of lap weld seams is ensured.

Description

Technical Field

[0001] This utility model belongs to the field of nuclear power welding and maintenance technology, specifically relating to a patch for repairing the lap weld of the bottom plate of a refueling tank. Background Technology

[0002] The main function of the refueling water tank in a nuclear power plant is to fill the reactor refueling pool with water when the unit is shut down for refueling. In the event of a loss-of-water accident in the reactor, it provides the necessary boron-containing water for the Emergency Air Shower System (EAS) and the Safety Injection System (RIS). If the refueling water tank leaks, it will affect the unit's operating status and the availability of dedicated safety facilities.

[0003] After the upper and lower plates of the refueling tank are spliced ​​together and welded into right-angle fillet welds, the residual tensile stress from the welding and the weight of the tank after it is filled with water will accumulate on the bottom plate, forming tensile stress. The refueling tank is installed on a concrete base containing chloride ions, and the outside of the tank is exposed to a humid atmosphere. Due to the combined effects of tensile stress, corrosive environment, and sensitive steel material, stress corrosion failure from the outside to the inside was found in the bottom plate of the refueling tank after long-term operation. For weld cracks found by non-destructive testing, plate-mounted welding is a common repair method. Utility Model Content

[0004] The purpose of this utility model is to provide a patch for repairing the lap weld of the bottom plate of a refueling water tank, solving the problem that existing repair methods for defects in the lap weld of the bottom plate of a refueling water tank cannot suppress the continued propagation of stress corrosion cracks. The patch has a length and width of not less than 150mm, and a thickness consistent with the thickness of the upper plate of the bottom plate of the refueling water tank. The upper bent part of the patch is attached to the upper plate of the bottom plate of the water tank, the bent connecting part is attached to the lap weld, and the lower bent part is attached to the lower plate of the bottom plate of the water tank. The patch can fit the lap weld and cover it by changing the bending angle between the bent connecting part and the upper and lower bent parts. When positioning the patch, the crack of the lap weld is covered at the middle position of the length direction of the bent connecting part of the patch.

[0005] The above-mentioned patch for repairing the lap weld of the bottom plate of the water tank is described in which the crack of the lap weld is located by ultrasonic detection method, the position of the patch is determined and placed, and then the patch is fixed by spot welding. After fixing, the patch is fully welded around its perimeter.

[0006] The aforementioned type of patch for repairing the lap weld seam of the bottom plate of a water tank is made of the same material as the bottom plate of the water tank where the lap weld seam needs to be repaired, namely stainless steel.

[0007] The aforementioned type of patch for repairing the lap weld of the bottom plate of a water tank undergoing refueling is wherein the length and width of the patch are not greater than the length and width of the upper and lower bottom plates of the water tank after splicing.

[0008] The above-mentioned patch for repairing the lap weld of the bottom plate of the water tank is provided in which the lap weld is ground before covering with the patch, the weld excess height is ground to be close to flush, and crack-stopping holes are drilled at the tip of the weld crack. Then the upper plate and the lower plate of the bottom plate of the water tank near the lap weld are polished.

[0009] The above-mentioned patch for repairing the lap weld of the bottom plate of the water tank is provided. Where the distance between two cracks in the length direction of the lap weld is no more than 100mm, a patch is used to cover the two cracks. At this time, the length of the patch is not less than L, where L = 150mm + the length distance between the two cracks.

[0010] Compared with the prior art, the beneficial effects of this utility model are: the patch plate provided by this utility model for repairing the lap weld of the bottom plate of the water tank can cover the lap weld and avoid crack propagation caused by welding stress, thereby achieving the purpose of inhibiting the continued propagation of stress corrosion cracks and ensuring the reliability of lap weld repair. Attached Figure Description

[0011] Figure 1 The diagram shown is a structural schematic of a patch for repairing the lap weld of the bottom plate of a refillable water tank according to the present invention.

[0012] Figure 2 The image shown is a side view of a patch for repairing the lap weld of the bottom plate of a refillable water tank according to this utility model.

[0013] Figure 3 The image shown is a top view of a patch for repairing the lap weld of the bottom plate of a water tank according to this utility model.

[0014] The following are the labels in the attached diagram: 1. Upper bend; 2. Bending connection; 3. Lower bend; 4. Lap weld; 5. Upper plate of the water tank bottom plate; 6. Lower plate of the water tank bottom plate. Detailed Implementation

[0015] To address the problem that repairing defects in the lap weld of the bottom plate of a refueling water tank cannot prevent the continued propagation of stress corrosion cracks, this utility model provides a patch for repairing the lap weld of the bottom plate of a refueling water tank. For example... Figures 1-3As shown, for a single crack in the lap weld, the length and width of the plate are both not less than 150mm, and the thickness is the same as the thickness of the bottom plate 5 of the water tank. The upper bent part 1 of the plate is attached to the bottom plate 5 of the water tank, the bent connecting part 2 is attached to the lap weld 4, and the lower bent part 3 is attached to the bottom plate 6 of the water tank. The plate can be attached to the lap weld 4 by changing the bending angle between the bent connecting part 2 and the upper bent part 1 and the lower bent part 3, and thus cover the lap weld 4. When positioning the plate, the crack in the lap weld 4 is covered at the middle position of the length direction of the bent connecting part 2 of the plate.

[0016] The length and width of the patch used for repairing the lap weld of the bottom plate of the water tank should not exceed the length and width of the spliced ​​upper plate 5 and lower plate 6 of the bottom plate of the water tank. At two cracks in the length direction of the lap weld 4, where the distance between them is no more than 100mm, a patch is used to cover the two cracks. The length of the patch should be no less than L, where L = 150mm + the distance between the two cracks.

[0017] All stress corrosion cracks in the lap weld 4 were located using ultrasonic testing. After location, the patch was placed in a position that covered the middle part of the lap weld 4 along its length. Before covering with the patch, the lap weld 4 was ground down to near flush with the weld reinforcement, and anti-crack holes were drilled at the crack tips. Then, the upper plate 5 and lower plate 6 of the water tank bottom plate within the patch coverage area near the lap weld 4 were polished. After placement, the patch was fixed by spot welding. After spot welding, the patch was welded around its perimeter using the same welding process as the lap weld. The material of the patch used for lap weld repair was the same as that of the water tank bottom plate requiring repair, both being 304L austenitic stainless steel. When fixing the patch by welding, it was necessary to avoid excessive welding current, which could cause stress corrosion cracks to be subjected to excessive welding thermal stress and propagate.

[0018] It should be noted that the combination of the technical features in the embodiments of this utility model is not limited to the combination methods recorded in the embodiments of this utility model or the combination methods recorded in specific embodiments. All technical features recorded in this utility model can be freely combined or combined in any way, unless there is a contradiction between them.

[0019] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications or equivalent substitutions made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A patch for repairing the lap weld seam of the bottom plate of a refueling water tank, characterized in that... The length and width of the patch plate are not less than 150mm, and the thickness is consistent with the thickness of the upper plate (5) of the water tank bottom plate; the upper bent part (1) of the patch plate is attached to the upper plate (5) of the water tank bottom plate, the bent connecting part (2) is attached to the lap weld (4), and the lower bent part (3) is attached to the lower plate (6) of the water tank bottom plate; the patch plate can be attached to the lap weld (4) by changing the bending angle between the bent connecting part (2) and the upper bent part (1) and the lower bent part (3), and the lap weld (4) is covered; when the patch plate is positioned, the crack of the lap weld (4) is covered in the middle position of the length direction of the bent connecting part (2) of the patch plate.

2. The patch for repairing the overlap weld of the bottom plate of a refueling water tank according to claim 1, characterized in that, The crack of the lap weld (4) is positioned by using ultrasonic detection method, and the position of the patch plate is determined for placement, and then the patch plate is fixed by spot welding, and the patch plate is fully welded around after being fixed.

3. The patch for repairing the overlap weld of the bottom plate of a refueling water tank according to claim 1, characterized in that, The material of the patch plate for repairing the lap weld is consistent with the water tank bottom plate that needs to be repaired, which is stainless steel.

4. The patch for repairing the overlap weld of the bottom plate of a refueling water tank according to claim 1, characterized in that, The length and width of the patch plate are not greater than the length and width of the upper plate (5) and the lower plate (6) of the water tank bottom plate after splicing.

5. The patch for repairing the overlap weld of the bottom plate of a refueling water tank according to claim 1, characterized in that, Before covering the patch plate, the lap weld (4) should be polished, the weld excess height should be polished to be close to flush, and the crack tip of the weld should be polished, and then the upper plate (5) and the lower plate (6) of the water tank bottom plate near the lap weld (4) should be polished.

6. The patch for repairing the overlap weld of the bottom plate of a refueling water tank according to claim 1, characterized in that, At two crack distances not greater than 100mm in the length direction of the lap weld (4), a patch plate is used to cover the two cracks, and the length of the patch plate is not less than L, L=150mm+the length distance between the two cracks.

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