CN117030144B - Grid helium leakage detection method - Google Patents
Grid helium leakage detection method Download PDFInfo
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- CN117030144B CN117030144B CN202311295046.6A CN202311295046A CN117030144B CN 117030144 B CN117030144 B CN 117030144B CN 202311295046 A CN202311295046 A CN 202311295046A CN 117030144 B CN117030144 B CN 117030144B
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- 238000001514 detection method Methods 0.000 title claims abstract description 174
- 239000001307 helium Substances 0.000 title claims abstract description 58
- 229910052734 helium Inorganic materials 0.000 title claims abstract description 58
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 238000003860 storage Methods 0.000 claims abstract description 86
- 238000000034 method Methods 0.000 claims abstract description 45
- 238000003466 welding Methods 0.000 claims abstract description 28
- 238000007789 sealing Methods 0.000 claims abstract description 23
- 238000009792 diffusion process Methods 0.000 claims description 23
- 238000012360 testing method Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000011229 interlayer Substances 0.000 abstract description 5
- 229910052793 cadmium Inorganic materials 0.000 description 10
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 10
- 239000002915 spent fuel radioactive waste Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- 238000005192 partition Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 239000011358 absorbing material Substances 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 239000012459 cleaning agent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
- G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B37/00—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00
- F04B37/10—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for special use
- F04B37/14—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for special use to obtain high vacuum
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
- G21C17/07—Leak testing
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Plasma & Fusion (AREA)
- High Energy & Nuclear Physics (AREA)
- Examining Or Testing Airtightness (AREA)
Abstract
The invention discloses a grid helium leak detection method, which comprises the following steps of: vacuumizing the storage sleeve sandwich structure through the reserved process hole; step 2: filling helium into the interlayer structure of the storage sleeve in a state of keeping vacuum degree, and keeping pressure; step 3: sealing and welding the reserved process holes under normal pressure after pressure relief; step 4: checking welding seams of the sandwich structure of the storage sleeve by adopting a suction gun method; step 5: and (3) placing the storage sleeve sandwich structure into a double-cylinder leakage detection tool for vacuumizing leakage detection to obtain a leakage detection result.
Description
Technical Field
The invention belongs to the technical field of cadmium spent fuel storage grillwork detection, and particularly relates to a grillwork helium leakage detection method.
Background
The cadmium spent fuel storage grillwork is used for safely storing spent fuel assemblies in a pool, and critical and assembly overheating accidents do not occur. 24 pieces of 6 multiplied by 6 storage grillwork are arranged in the spent fuel storage pool, each cadmium spent fuel storage grillwork consists of 36 storage sleeves, each storage sleeve is a square sleeve with an inner cavity, the inner wall of the square sleeve is a stainless steel pipe with the thickness of 2mm, the lower part of the square sleeve is welded with a bottom plate with the thickness of 20mm to form a storage cavity of the fuel assembly, the storage cavity is 4265mm in height, a neutron absorbing material cadmium plate with the height of 3730mm and the thickness of 0.5mm is coated outside the storage cavity, and a layer of stainless steel plate with the thickness of 0.8mm is coated outside the cadmium plate. Thus, the two layers of stainless steel plates sandwich the cadmium plate, the two ends of the stainless steel plates are sealed by continuous welding seams, and 100% helium leakage inspection is required for the sandwich structure, so that the cadmium plate is ensured not to be contacted with water.
However, because the outer tube of the cadmium spent fuel storage grillwork is only 0.8mm, when the leakage of the inflated helium is detected, the bulge is extremely easy to generate, so that the product is invalid, each outer tube of the cadmium spent fuel storage grillwork (namely, the storage sleeve) is required to be detected independently, the workload is large, the detection requirement leakage value is low, the conventional detection means is difficult to meet the requirement, and the efficiency is low, so that a special tool is required to be developed, the detection is carried out at a reasonable time, the production period of the equipment can be shortened on the basis of ensuring the quality of the product, and a foundation is provided for the mass production of the equipment.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a grid helium leak detection method.
In order to solve the technical problems, the technical scheme of the invention is as follows: a grid helium leak detection method comprises the following steps,
step 1: vacuumizing the storage sleeve sandwich structure through the reserved process hole;
step 2: filling helium into the interlayer structure of the storage sleeve in a state of keeping vacuum degree, and keeping pressure;
step 3: sealing and welding the reserved process holes under normal pressure after pressure relief;
step 4: checking welding seams of the sandwich structure of the storage sleeve by adopting a suction gun method;
step 5: and (3) placing the storage sleeve sandwich structure into a double-cylinder leakage detection tool for vacuumizing leakage detection to obtain a leakage detection result.
Preferably, the step 1 specifically includes: and covering the reserved process hole of the storage sleeve sandwich structure by using the sealing cover, connecting the vacuum pump to the sealing cover, and starting vacuumizing the storage sleeve sandwich structure to below 10 pa.
Preferably, the step 2 specifically includes: and slowly filling helium into the sealed cover until the gauge pressure is 0.02MPa under the condition of keeping the vacuum degree in the sealed cover.
Preferably, the step 3 specifically includes: and removing the sealing cover after pressure relief, and performing sealing welding on the reserved process hole by adopting argon arc welding under normal pressure.
Preferably, the step 4 specifically includes: and calibrating the leak detector by using a helium-permeable standard leak, connecting a suction gun after calibrating the leak detector, calibrating the suction gun by using the standard leak, and pre-detecting a welding line of the storage sleeve sandwich structure after the calibration is finished to eliminate possible leakage of the storage sleeve sandwich structure.
Preferably, the step 5 specifically includes: step 5-1: vacuumizing a first leakage detecting cylinder and a second leakage detecting cylinder of the double-cylinder leakage detecting tool, connecting the first leakage detecting cylinder and the second leakage detecting cylinder with a vacuum leakage detecting system through a vacuum corrugated pipe, testing the background of the double-cylinder leakage detecting tool, and checking the effective minimum detectable leakage rate of leakage detection by using standard leakage holes connected to the first leakage detecting cylinder and the second leakage detecting cylinder;
step 5-2: closing the first vacuumizing valve or the second vacuumizing valve, and opening standard leak holes arranged on the first leak detection cylinder and the second leak detection cylinder for calibration;
step 5-3: placing the helium filled storage sleeve sandwich structure into a first leakage detection cylinder or a second leakage detection cylinder of a double-cylinder leakage detection tool, opening a vacuumizing valve, vacuumizing the first leakage detection cylinder or the second leakage detection cylinder to be smaller than 300Pa by using a mobile vacuum pump unit, vacuumizing the first leakage detection cylinder or the second leakage detection cylinder by using a diffusion unit in turn, vacuumizing the first leakage detection cylinder or the second leakage detection cylinder to be 2.5-4 Pa, and measuring the leakage rate of a leakage hole of the storage sleeve sandwich structure to output an indicated value;
step 5-4: after the measurement is finished, the leak detection container is put into air, and the interlayer structure of the storage sleeve is taken out;
step 5-5: and calculating the leak rate of the leak hole of the storage sleeve sandwich structure.
Preferably, the calculation formula of the effective minimum detectable leakage rate is as follows:
wherein:
in: leak detector noise signal value;
i: outputting a signal value by the standard leak hole;
I 0 : a background value of the vacuum leak detection system;
Q 0 : and calibrating the nominal leak rate of the leak hole.
Preferably, the calculation formula of the leak rate of the storage sleeve sandwich structure 1 is as follows:
wherein:
Q 2 : storing the helium leak rate of the sleeve sandwich structure leak hole;
Q 1 : a reference leak helium leak rate;
i: outputting an indication value by referring to the leak hole;
I 1 : storing the output indication value of the sleeve sandwich structure leak;
I 0 : background value of vacuum leak detection system.
Preferably, the vacuum leak detection system comprises a diffusion unit and a leak detector, wherein one end of the diffusion unit is connected with the leak detector, and the other end of the diffusion unit is connected with the double-cylinder leak detection tool.
Preferably, the double-cylinder leak detection tool comprises a first leak detection cylinder, a second leak detection cylinder, a first vacuumizing valve, a second vacuumizing valve, a third vacuumizing valve, a fourth vacuumizing valve, a standard leak and a movable vacuum pump unit, wherein one end of the first leak detection cylinder is connected with the diffusion unit through the first vacuumizing valve, the side wall of the first leak detection cylinder is connected with the movable vacuum pump unit through the third vacuumizing valve, one end of the second leak detection cylinder is connected with the diffusion unit through the second vacuumizing valve, the side wall of the second leak detection cylinder is connected with the movable vacuum pump unit through the fourth vacuumizing valve, and the movable vacuum pump unit is connected with the standard leak; the first leakage detection cylinder is also connected with a first air release valve and a first vacuum gauge, and the second leakage detection cylinder is also connected with a second air release valve and a second vacuum gauge; the first leakage detecting cylinder and the second leakage detecting cylinder are composed of two leakage detecting container flanges, two end faces of each leakage detecting container flange are respectively connected with the two leakage detecting container flanges, one leakage detecting container flange is connected with the first vacuumizing valve or the second vacuumizing valve through a vacuum bellows, and the side wall of each leakage detecting container is connected with the first vacuumizing gauge or the second vacuumizing gauge and the third vacuumizing valve or the fourth vacuumizing valve.
Compared with the prior art, the invention has the advantages that:
(1) The invention discloses a grid helium leak detection method, which comprises the steps of vacuumizing a storage sleeve sandwich structure through a reserved process hole, filling helium into the storage sleeve sandwich structure under the state of keeping vacuum degree, keeping pressure, sealing and welding the reserved process hole under normal pressure after pressure relief, then checking a welding seam of the storage sleeve sandwich structure by adopting a suction gun method, and finally placing the storage sleeve sandwich structure into a double-cylinder leak detection tool for vacuumizing leak detection to obtain a leak detection result.
(2) The invention firstly uses a suction gun method to inspect the welding seam of the sandwich structure of the storage sleeve, eliminates large leakage, avoids background rise when leakage detection is caused by leakage of a large amount of helium gas to the leakage detection cylinder, then places the leakage detection cylinder into a double-cylinder leakage detection tool for vacuumizing, and realizes higher detection sensitivity by using pressure difference increase;
(3) The invention adopts a movable vacuum pump unit to vacuumize and charge helium, the storage sleeves are placed side by side, 1 personal operation tool is arranged on the storage sleeves, the pressure of the sealing gasket is regulated by a bolt, and the pressure of the vacuumization and helium charging is controlled by a manual regulating valve; batch detection after the storage sleeves are placed can be realized, a crane and labor are not required to be occupied, labor is saved, the occupied space is reduced, and the working efficiency is improved by about 4 times compared with the prior art;
(4) According to the invention, a double-cylinder leak detection tool is adopted to carry out double-cylinder detection, a group of leak detection cylinders are vacuumized to be smaller than 300Pa by using a movable vacuum pump unit, and then the leak detection cylinders are alternately vacuumized to be 2.5-4 Pa by using a diffusion unit, so that the time for carrying out low pumping by using the diffusion unit is reduced, and the detection efficiency is improved by about 30%.
Drawings
FIG. 1 is a process flow diagram of a method for detecting a grid helium leak in accordance with the present invention;
FIG. 2 is a schematic helium-filled diagram of a storage jacket sandwich of the present invention;
FIG. 3 is a schematic diagram of a dual-cylinder leak detection tool according to the present invention;
fig. 4 is a schematic diagram of helium leak detection using a dual-cylinder leak detection tool for a storage casing sandwich structure of the present invention.
Reference numerals illustrate:
1. a storage sleeve sandwich structure, a double-cylinder leak detection tool, a sealing cover, a vacuum leak detection system and a sealing cover;
1-1, reserving a process hole, 1-2, an outer sleeve, 1-3 and a partition plate interlayer;
4-1, a diffusion unit, 4-2, and a leak detector;
2-1, a first leakage detection cylinder, 2-2, a second leakage detection cylinder, 2-3, a first vacuumizing valve, 2-4, a second vacuumizing valve, 2-5, a third vacuumizing valve, 2-6, a fourth vacuumizing valve, 2-7, a standard leak, 2-8, a movable vacuum pump unit, 2-9, a first air release valve, 2-10, a first vacuum gauge, 2-11, a second air release valve, 2-12, a second vacuum gauge, 2-13, a leakage detection container, 2-14 and a leakage detection container flange.
Detailed Description
The following describes specific embodiments of the present invention with reference to examples:
it should be noted that the structures, proportions, sizes and the like illustrated in the present specification are used for being understood and read by those skilled in the art in combination with the disclosure of the present invention, and are not intended to limit the applicable limitations of the present invention, and any structural modifications, proportional changes or size adjustments should still fall within the scope of the disclosure of the present invention without affecting the efficacy and achievement of the present invention.
Example 1
As shown in fig. 1, the invention discloses a grid helium leak detection method, which comprises the following steps,
step 1: vacuumizing the storage sleeve sandwich structure 1 through the reserved process hole 1-1;
step 2: filling helium into the storage sleeve sandwich structure 1 under the vacuum state, and maintaining the pressure;
step 3: sealing and welding the reserved process hole 1-1 under normal pressure after pressure relief;
step 4: checking the welding seam of the storage sleeve sandwich structure 1 by adopting a suction gun method;
step 5: and (3) placing the storage sleeve sandwich structure 1 into a double-cylinder leakage detection tool 2 for vacuumizing leakage detection to obtain a leakage detection result.
Example 2
As shown in fig. 2, preferably, the step 1 specifically includes: the reserved process hole 1-1 of the storage sleeve sandwich structure 1 is covered by the sealing cover 3, and a vacuum pump is connected to the sealing cover 3, so that the storage sleeve sandwich structure 1 is vacuumized to be less than 10 pa.
The storage sleeve sandwich structure 1 comprises an outer sleeve 1-2 and a partition plate sandwich layer 1-3, wherein the outer sleeve 1-2 is sleeved outside the partition plate sandwich layer 1-3, and a reserved process hole 1-1 is formed in the outer sleeve 1-2.
Preferably, the step 2 specifically includes: and slowly filling helium into the sealed cover 3 until the gauge pressure is 0.02MPa under the condition that the vacuum degree in the sealed cover 3 is kept.
Example 3
Preferably, the step 3 specifically includes: and removing the sealing cover 3 after pressure relief, and performing sealing welding on the reserved process hole 1-1 by adopting argon arc welding under normal pressure.
Preferably, the step 4 specifically includes: the leak detector is calibrated by using a helium-permeable standard leak, the suction gun is connected after the leak detector is calibrated, the suction gun is calibrated by using the standard leak, and the welding seam of the storage sleeve sandwich structure 1 is pre-detected after the calibration is finished, so that the possible leakage of the storage sleeve sandwich structure 1 is eliminated.
Example 4
Preferably, the step 5 specifically includes: step 5-1: vacuumizing a first leakage detection cylinder 2-1 and a second leakage detection cylinder 2-2 of a double-cylinder leakage detection tool 2, connecting the first leakage detection cylinder 2-1 and the second leakage detection cylinder 2-2 with a vacuum leakage detection system 4 through a vacuum corrugated pipe, testing the background of the double-cylinder leakage detection tool 2, and checking the effective minimum detectable leakage rate of leakage detection by using standard leakage holes 2-7 connected to the first leakage detection cylinder 2-1 and the second leakage detection cylinder 2-2;
checking the effective minimum leak rate for leak detection is used to verify that the system can detect the minimum leak rate.
Step 5-2: closing the first vacuumizing valve 2-3 or the second vacuumizing valve 2-4, and opening the standard leak holes 2-7 arranged on the first leak detection cylinder 2-1 and the second leak detection cylinder 2-2 for calibration;
step 5-3: placing the helium filled storage sleeve sandwich structure 1 into a first leakage detection cylinder 2-1 or a second leakage detection cylinder 2-2 of a double-cylinder leakage detection tool 2, opening a vacuumizing valve, vacuumizing the first leakage detection cylinder 2-1 or the second leakage detection cylinder 2-2 to be smaller than 300Pa by using a movable vacuum pump unit 2-8, vacuumizing the first leakage detection cylinder 2-1 or the second leakage detection cylinder 2-2 by using a diffusion unit 4-1 alternately, vacuumizing the first leakage detection cylinder 2-1 or the second leakage detection cylinder 2-2 to be higher than 2.5-4 Pa, and measuring the leak rate of the storage sleeve sandwich structure 1 to output an indicated value;
step 5-4: after the measurement is finished, the leak detection containers 2-13 are put into air, and the storage sleeve sandwich structure 1 is taken out;
step 5-5: the leak rate of the storage sleeve sandwich 1 was calculated.
Example 5
Preferably, the calculation formula of the effective minimum detectable leakage rate is as follows:
wherein:
in: leak detector noise signal value;
i: outputting a signal value by the standard leak hole;
I 0 : a background value of the vacuum leak detection system;
Q 0 : and calibrating the nominal leak rate of the leak hole.
Preferably, the calculation formula of the leak rate of the leak hole of the storage sleeve sandwich structure (1) is as follows:
wherein:
Q 2 : storing the helium leak rate of the sleeve sandwich structure leak hole;
Q 1 : helium leak rate of reference leak (10) -10 Pa m 3 S helium permeation type standard leak hole);
i: outputting an indication value by referring to the leak hole;
I 1 : storing the output indication value of the sleeve sandwich structure leak;
I 0 : background value of vacuum leak detection system.
Example 6
As shown in fig. 3 and 4, preferably, the vacuum leak detection system 4 includes a diffusion unit 4-1 and a leak detector 4-2, one end of the diffusion unit 4-1 is connected with the leak detector 4-2, and the other end of the diffusion unit 4-1 is connected with the double-cylinder leak detection tool 2.
As shown in fig. 3 and 4, the double-cylinder leak detection tool 2 comprises a first leak detection cylinder 2-1, a second leak detection cylinder 2-2, a first vacuumizing valve 2-3, a second vacuumizing valve 2-4, a third vacuumizing valve 2-5, a fourth vacuumizing valve 2-6, a standard leak hole 2-7 and a movable vacuum pump unit 2-8, wherein one end of the first leak detection cylinder 2-1 is connected with the diffusion unit 4-1 through the first vacuumizing valve 2-3, the side wall of the first leak detection cylinder 2-1 is connected with the movable vacuum pump unit 2-8 through the third vacuumizing valve 2-5, one end of the second leak detection cylinder 2-2 is connected with the diffusion unit 4-1 through the second vacuumizing valve 2-4, the side wall of the second leak detection cylinder 2-2 is connected with the movable vacuum pump unit 2-8 through the fourth vacuumizing valve 2-6, and the movable vacuum pump unit 2-8 is connected with the standard leak hole 2-7; the first leakage detection cylinder 2-1 is also connected with a first air release valve 2-9 and a first vacuum gauge 2-10, and the second leakage detection cylinder 2-2 is also connected with a second air release valve 2-11 and a second vacuum gauge 2-12; the first leakage detecting cylinder 2-1 and the second leakage detecting cylinder 2-2 are composed of two leakage detecting containers 2-13 and two leakage detecting container flanges 2-14, two end faces of the leakage detecting containers 2-13 are respectively connected with the leakage detecting container flanges 2-14, one leakage detecting container flange 2-14 is connected with the first vacuumizing valve 2-3 or the second vacuumizing valve 2-4 through a vacuum bellows, the side wall of the leakage detecting container 2-13 is connected with the first vacuumizing gauge 2-10 or the second vacuumizing gauge 2-12, and the third vacuumizing valve 2-5 or the fourth vacuumizing valve 2-6.
Example 7
Step 1), a sealing cover 3 is used for covering the part of the reserved process hole 1-1 of the storage sleeve sandwich structure 1, and a vacuum pump is connected to vacuumize the sandwich from the atmosphere to a unit vacuum gauge for measuring the vacuum degree.
And 2) filling helium into the cover until the gauge pressure is 0.02MPa under the condition of keeping the vacuum degree in the cover.
And 3) performing seal welding on the reserved process hole 1-1 under normal pressure after pressure relief.
Step 4) calibrating the leak detector by using a helium-permeable standard leak according to the instrument operation instruction; and after the leak detector is calibrated, a suction gun is connected, a standard leak orifice is used for calibrating a suction gun method, and the welding line of the outer sleeve is detected (as the initial detection of the whole detection of the sleeve, the position of a leak point is determined, and the large leak is eliminated).
Step 5) when helium is filled into the interlayer of the storage sleeve, the helium pollution to the surface of the sleeve caused by helium is reduced as much as possible, and cleaning agent is carried out on the helium filling port;
step 5-1: the method comprises the steps of vacuumizing a first leakage detecting cylinder 2-1 and a second leakage detecting cylinder 2-2 of a double-cylinder leakage detecting tool 2, connecting the first leakage detecting cylinder 2-1 and the second leakage detecting cylinder 2-2 with a vacuum leakage detecting system 4 through a vacuum corrugated pipe, testing the background of the double-cylinder leakage detecting tool 2, and checking the effective minimum detectable leakage rate of leakage detection by using a standard leakage hole 2-7 connected to the first leakage detecting cylinder 2-1 and the second leakage detecting cylinder 2-2, wherein the specific formula is as follows:
(calculation formula of minimum leak detection rate of leak detection system by vacuum leak detection calculation)
Wherein:
in: leak detector noise signal value;
i: outputting a signal value by the standard leak hole;
I 0 : a background value of the vacuum leak detection system;
Q 0 : and calibrating the nominal leak rate of the leak hole.
Step 5-2: closing the vacuumizing valve, putting air into the leakage detection container to keep a balanced state, and opening a calibration leak hole arranged on the leakage detection container for calibration.
Step 5-3: and placing the helium filled storage sleeve into a leak detection tool, opening a vacuumizing valve, vacuumizing the leak detection tool, and measuring the output value of the leak rate of the leak hole of the grid assembly.
Step 5-4: after the measurement is finished, the leak detection container is put into air, the end cover is opened, and the storage sleeve is taken out.
Step 5-5: the leak rate of the cadmium grid assembly can be calculated by the following steps:
(formula for calculating leak rate of helium leak detection to detected piece by vacuum method)
Wherein:
Q 2 -storing the leak helium rate of the sleeve sandwich;
Q 1 -reference leak helium leak rate, 10 -10 Pa m 3 S helium-permeable standard leak;
i, outputting an indicated value of the reference leak hole;
I 1 -an output indication of the leak of the sandwich construction of the storage sleeve;
I 0 -vacuum leak detection system background value.
The storage sleeve is detected for a plurality of times through a single cylinder and a double cylinder respectively, wherein the single cylinder detection is shown in a table 1, and the double cylinder detection is shown in a table 2:
table 1 single cartridge test results
| Sequence number | Numbering device | I 0 | Q 2 | Single tube detecting time |
| 1 | C5-31 | 1.1×10 -10 Pa•m 3 /s | 4.7×10 -10 Pa•m 3 /s | 23.3 minutes |
| 2 | C5-32 | 1.2×10 -10 Pa•m 3 /s | 2.8×10 -10 Pa•m 3 /s | 21.9 minutes |
| 3 | C6-27 | 1.2×10 -10 Pa•m 3 /s | 3.0×10 -10 Pa•m 3 /s | 20.4 minutes |
| 4 | C6-26 | 1.0×10 -10 Pa•m 3 /s | 2.6×10 -10 Pa•m 3 /s | 21.5 minutes |
| 5 | C7-12 | 1.2×10 -10 Pa•m 3 /s | 2.4×10 -10 Pa•m 3 /s | 24.2 minutes |
| 6 | C7-13 | 1.1×10 -10 Pa•m 3 /s | 2.4×10 -10 Pa•m 3 /s | 23.9 minutes |
Table 2 results of double cylinder test
The single-cylinder detection and the double-cylinder detection have no great change from the actually measured leak rate data, and all meet the upstream technical conditions, and the detection time is greatly reduced.
The working principle of the invention is as follows:
as shown in fig. 1-4, the invention discloses a grid helium leak detection method, which comprises the steps of firstly vacuumizing a storage sleeve sandwich structure 1 through a reserved process hole 1-1, then filling helium into the storage sleeve sandwich structure 1 in a state of keeping vacuum degree, and keeping pressure; then, after pressure relief, carrying out seal welding on the reserved process hole 1-1 under normal pressure; and then, adopting a suction gun method to test the welding seam of the storage sleeve sandwich structure 1, and finally, placing the storage sleeve sandwich structure 1 into a double-cylinder leakage detection tool 2 for vacuumizing leakage detection to obtain a leakage detection result.
The invention discloses a grid helium leak detection method, which comprises the steps of vacuumizing a storage sleeve sandwich structure through a reserved process hole, filling helium into the storage sleeve sandwich structure under the state of keeping vacuum degree, keeping pressure, sealing and welding the reserved process hole under normal pressure after pressure relief, then checking a welding seam of the storage sleeve sandwich structure by adopting a suction gun method, and finally placing the storage sleeve sandwich structure into a double-cylinder leak detection tool for vacuumizing leak detection to obtain a leak detection result.
The invention firstly uses a suction gun method to inspect the welding seam of the sandwich structure of the storage sleeve, eliminates large leakage, avoids background rise when leakage detection is caused by leakage of a large amount of helium gas to the leakage detection cylinder, then places the leakage detection cylinder into a double-cylinder leakage detection tool for vacuumizing, and realizes higher detection sensitivity by using pressure difference increase.
The invention adopts a movable vacuum pump unit to vacuumize and charge helium, the storage sleeves are placed side by side, 1 personal operation tool is arranged on the storage sleeves, the pressure of the sealing gasket is regulated by a bolt, and the pressure of the vacuumization and helium charging is controlled by a manual regulating valve; the batch detection after the storage sleeve is put can be realized, a crane and manpower are not required to be occupied, the manpower is saved, the occupied space is reduced, and the working efficiency is improved by about 4 times compared with the prior art.
According to the invention, a double-cylinder leak detection tool is adopted to carry out double-cylinder detection, a group of leak detection cylinders are vacuumized to be smaller than 300Pa by using a movable vacuum pump unit, and then the leak detection cylinders are alternately vacuumized by using a diffusion unit for 2.5-4 Pa, so that the time for carrying out low pumping by using the diffusion unit is reduced, and the detection efficiency is improved by about 30%.
While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Many other changes and modifications may be made without departing from the spirit and scope of the invention. It is to be understood that the invention is not to be limited to the specific embodiments, but only by the scope of the appended claims.
Claims (8)
1. A grid helium leak detection method is characterized by comprising the following steps,
step 1: vacuumizing the storage sleeve sandwich structure (1) through the reserved process hole (1-1);
step 2: filling helium into the storage sleeve sandwich structure (1) under the state of keeping the vacuum degree, and keeping the pressure;
step 3: sealing and welding the reserved process hole (1-1) under normal pressure after pressure relief;
step 4: checking welding seams of the storage sleeve sandwich structure (1) by adopting a suction gun method;
step 5: placing the storage sleeve sandwich structure (1) into a double-cylinder leak detection tool (2) for vacuumizing leak detection to obtain a leak detection result;
step 5-1: vacuumizing a first leakage detecting cylinder (2-1) and a second leakage detecting cylinder (2-2) of a double-cylinder leakage detecting tool (2), connecting the first leakage detecting cylinder (2-1) and the second leakage detecting cylinder (2-2) with a vacuum leakage detecting system (4) through a vacuum corrugated pipe, testing the background of the double-cylinder leakage detecting tool (2), and checking the effective minimum detectable leakage rate of leakage detection by utilizing standard leakage holes (2-7) connected to the first leakage detecting cylinder (2-1) and the second leakage detecting cylinder (2-2);
step 5-2: closing the first vacuumizing valve (2-3) or the second vacuumizing valve (2-4), and opening the standard leak holes (2-7) arranged on the first leak detection cylinder (2-1) and the second leak detection cylinder (2-2) for calibration;
step 5-3: placing the helium filled storage sleeve sandwich structure (1) into a first leakage detecting cylinder (2-1) or a second leakage detecting cylinder (2-2) of a double-cylinder leakage detecting tool (2), opening a vacuumizing valve, vacuumizing the first leakage detecting cylinder (2-1) or the second leakage detecting cylinder (2-2) to be smaller than 300Pa by using a movable vacuum pump unit (2-8), vacuumizing the first leakage detecting cylinder (2-1) or the second leakage detecting cylinder (2-2) by using a diffusion unit (4-1) alternately, vacuumizing the first leakage detecting cylinder (2-1) or the second leakage detecting cylinder (2-2) to be 2.5-4 Pa, and measuring the leakage rate of a leakage hole of the storage sleeve sandwich structure (1) to output an indicated value;
step 5-4: after the measurement is finished, the leak detection container (2-13) is put into air, and the storage sleeve sandwich structure (1) is taken out;
step 5-5: calculating the leak rate of the leak hole of the storage sleeve sandwich structure (1);
the double-cylinder leakage detection tool (2) comprises a first leakage detection cylinder (2-1), a second leakage detection cylinder (2-2), a first vacuumizing valve (2-3), a second vacuumizing valve (2-4), a third vacuumizing valve (2-5), a fourth vacuumizing valve (2-6), a standard leakage hole (2-7) and a movable vacuum pump unit (2-8), wherein one end of the first leakage detection cylinder (2-1) is connected with the diffusion unit (4-1) through the first vacuumizing valve (2-3), the side wall of the first leakage detection cylinder (2-1) is connected with the movable vacuum pump unit (2-8) through the third vacuumizing valve (2-5), one end of the second leakage detection cylinder (2-2) is connected with the diffusion unit (4-1) through the second vacuumizing valve (2-4), the side wall of the second leakage detection cylinder (2-2) is connected with the movable vacuum pump unit (2-8) through the fourth vacuumizing valve (2-6), and the movable vacuum pump unit (2-8) is connected with the standard leakage hole (2-7); the first leakage detection barrel (2-1) is also connected with a first air release valve (2-9) and a first vacuum gauge (2-10), and the second leakage detection barrel (2-2) is also connected with a second air release valve (2-11) and a second vacuum gauge (2-12); the leakage detection device is characterized in that each of the first leakage detection barrel (2-1) and the second leakage detection barrel (2-2) consists of two leakage detection containers (2-13) and two leakage detection container flanges (2-14), wherein two end faces of each leakage detection container (2-13) are respectively connected with each leakage detection container flange (2-14), one leakage detection container flange (2-14) is connected with a first vacuumizing valve (2-3) or a second vacuumizing valve (2-4) through a vacuum bellows, and the side wall of each leakage detection container (2-13) is connected with a first vacuum gauge (2-10) or a second vacuum gauge (2-12) and a third vacuumizing valve (2-5) or a fourth vacuumizing valve (2-6).
2. The method for detecting helium grid leakage according to claim 1, wherein the step 1 is specifically: and covering the reserved process hole (1-1) of the storage sleeve sandwich structure (1) by using the sealing cover (3), connecting a vacuum pump to the sealing cover (3), and starting vacuumizing the storage sleeve sandwich structure (1) to below 10 pa.
3. The method for detecting helium grid leakage according to claim 2, wherein the step 2 is specifically: and slowly filling helium into the sealed cover (3) until the gauge pressure is 0.02MPa under the condition of keeping the vacuum degree in the sealed cover (3).
4. A method of detecting helium grid leakage according to claim 3, wherein: the step 3 specifically comprises the following steps: and removing the sealing cover (3) after pressure relief, and performing sealing welding on the reserved process hole (1-1) by adopting argon arc welding under the normal pressure state.
5. A method of detecting helium in a grid according to claim 1, wherein: the step 4 specifically comprises the following steps: and calibrating the leak detector by using a helium-permeable standard leak, connecting a suction gun after calibrating the leak detector, calibrating the suction gun by using the standard leak, and pre-detecting a welding seam of the storage sleeve sandwich structure (1) after the calibration is finished to eliminate possible leakage of the storage sleeve sandwich structure (1).
6. A method of detecting helium in a grid according to claim 1, wherein: the calculation formula of the effective minimum detectable leakage rate is as follows:
wherein:
in: leak detector noise signal value;
i: outputting a signal value by the standard leak hole;
I 0 : a background value of the vacuum leak detection system;
Q 0 : and calibrating the nominal leak rate of the leak hole.
7. A method of detecting helium in a grid according to claim 1, wherein: the calculation formula of the leak rate of the leak hole of the storage sleeve sandwich structure (1) is as follows:
wherein:
Q 2 : storing the helium leak rate of the sleeve sandwich structure leak hole;
Q 1 : a reference leak helium leak rate;
i: outputting an indication value by referring to the leak hole;
I 1 : storing the output indication value of the sleeve sandwich structure leak;
I 0 : background value of vacuum leak detection system.
8. A method of detecting helium in a grid according to claim 1, wherein: the vacuum leak detection system (4) comprises a diffusion unit (4-1) and a leak detector (4-2), wherein one end of the diffusion unit (4-1) is connected with the leak detector (4-2), and the other end of the diffusion unit (4-1) is connected with the double-cylinder leak detection tool (2).
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