CN109520678B - Pressure maintaining detection method for pressure vessel air tightness test - Google Patents

Pressure maintaining detection method for pressure vessel air tightness test Download PDF

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CN109520678B
CN109520678B CN201811605250.2A CN201811605250A CN109520678B CN 109520678 B CN109520678 B CN 109520678B CN 201811605250 A CN201811605250 A CN 201811605250A CN 109520678 B CN109520678 B CN 109520678B
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pressure
value
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tightness test
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CN109520678A (en
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高飞
林俊辉
尤黄宇
卢书芳
张元鸣
肖刚
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Zhejiang University of Technology ZJUT
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    • 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
    • G01M3/06—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point by observing bubbles in a liquid pool
    • G01M3/10—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point by observing bubbles in a liquid pool for containers, e.g. radiators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/13—Edge detection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/10—Segmentation; Edge detection
    • G06T7/136—Segmentation; Edge detection involving thresholding
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10016—Video; Image sequence

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  • Examining Or Testing Airtightness (AREA)

Abstract

The invention provides a pressure maintaining detection method for an air tightness test of a pressure container, which can automatically detect the pressure containers and the number of the pressure containers in a detection pool, acquire the internal pressure value of the pressure container through a pressure sensor when the pressure containers exist in the detection pool, and further calculate whether the pressure maintaining pressure and the pressure maintaining time of the pressure container reach a rated value according to the change of the pressure value, thereby avoiding the condition of sub-detection in the air tightness detection.

Description

Pressure maintaining detection method for pressure vessel air tightness test
Technical Field
The invention relates to the field of industrial air tightness detection, in particular to a pressure maintaining detection method for an air tightness test of a pressure container.
Background
Pressure vessels are commonly used in the industry to store compressed liquids or gases. For such a pressure vessel which needs to be filled with high-pressure gas or liquid, if leakage occurs during use, a safety hazard will be caused, and in severe cases, dangerous events such as fire and explosion will be caused. At present, most manufacturers adopt a water immersion method to detect the air tightness of a pressure container. The water immersion method is that a pressure container to be detected is placed in an air tightness detection pool, then gas is filled into the pressure container to be detected, so that the air pressure in the pressure container reaches a detection standard, and the air tightness of the pressure container is judged by observing whether bubbles emerge from the detection pool or not. The standard GB12137-89 gas cylinder airtightness test method released by the State technical supervision agency (SOA) is specifically stipulated as follows: in the test process, whether the pressure is added in place or not, whether the time keeping time is enough or not, whether the test is normal or not before each pressure container leaves the factory or not and the like relate to the use safety after the pressure container enters the market. In the manual implementation process, in order to improve the production efficiency, part of manufacturers perform sub-inspection in the air tightness detection process due to insufficient pressure loaded inside the pressure container or insufficient duration of the loading pressure by detection personnel.
Aiming at the detection of the pressure condition in the air tightness test, experts and scholars at home and abroad develop key researches. The technical scheme which is closer to the invention comprises the following steps: in order to improve the detection precision of the differential pressure method, Anthony Jenkins and the like (Temperature compensation in differential pressure loss detection [ P ]. United States Patent:4947352,1990-08-07), a scale factor is provided and is determined according to multiple measurements, so that the error caused by the detection of the differential pressure method is reduced. Sarkis Barkhoudarian et al (Leak detection system with background compensation [ P ]. United States Patent:5001346,1991-03-19) propose to keep the tested piece and the standard piece in a relatively constant environment, reducing the influence of the heat transfer outside the airtight container on the detection accuracy of the differential pressure method. Kenji Kawashima et al (Analysis of temperature effect on differential pressure detection [ A ]. SICE 2004 annular reference [ C ]. Oakland: IEEE Computer Press,2004: 159-. Harus L G et al (dynamic Model of Leak Measurement by pneumatic pressure Change [ M ]. Japan: Systems Modeling and Simulation,2007) studied the influence of temperature on the detection by the differential pressure method, and proposed a Model of the relationship between the external temperature and the detection accuracy by the differential pressure method. Chenyu et al (design and implementation of differential pressure air tightness detector [ J ]. proceedings of China institute of metrology, 2009,20(4):311-314) developed an air tightness detector based on a differential pressure method, controlled the air inflation and deflation process by a circuit, improved human-computer interaction by adopting a touch screen module, and configured with a high-precision pressure sensor to improve the detection precision. The automatic acquisition system of the steel cylinder inspection data is developed by the admiration pigeon and the like (design [ J ] of the automatic acquisition system of the steel cylinder inspection data, 2011,32(4):56-58), and the like, and is mainly used for acquiring data such as inspection pressure, temperature and the like in real time. Roxamine and the like (research on a PLC-based airtightness detector calibration device [ J ]. measurement technique, 2015,25(1):94-95) and the like have been studied for the differential pressure method, and a PLC-based airtightness calibration device has been designed to improve the measurement accuracy by the differential pressure method. Liuhao et al (based on external pressure differential method high pressure valve airtightness detection system research [ J ]. lathe and hydraulic pressure, 2015,43(1):53-56) propose a set of detection scheme for steel cylinder valve airtightness based on external pressure differential method aiming at the defect that the detection precision of direct pressure method and internal pressure differential method is influenced by gas leakage of steel cylinder valve and gas guide tube. Experiments show that the scheme improves the detection precision to a certain extent, accelerates the detection speed and has good system stability. The method for detecting the leakage of the aerostat is provided by Zengvanyang and the like (research [ J ]. journal of university of fertilizer industry (natural science edition), 2018,41(04): 451-plus 456, based on an equivalent differential pressure method) and comprises the steps of carrying out mathematical modeling on the aerostat at different temperature and differential pressure change parameters, verifying and correcting a simulation model by using a large amount of data, and enabling the model to accurately calculate the leakage of the aerostat after measuring the change of the temperature and the differential pressure of the aerostat within a period of time.
In summary, compared with the currently proposed air tightness test scheme, the main problems are that: most of the schemes have a focus on how to detect a gas leakage pressure container by a pressure difference method and other methods, and in fact, whether the pressure container to be detected leaks gas or not, whether the pressure holding pressure and the pressure holding time of the pressure container reach the standard or not is ensured in the gas tightness detection process, and the final gas tightness detection result is directly influenced by neglecting the pressure holding pressure and the pressure holding time of the pressure container.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a pressure maintaining detection method for the air tightness test of a pressure container.
The technical scheme of the invention is as follows:
a pressure maintaining detection method for a pressure vessel airtightness test is characterized by comprising the following steps:
step 1: shooting the air tightness test detection pool by an industrial camera, and obtaining a video frame image f from the camera i1,2,.., n, graying fiObtaining a gray image gfiUsing 3 x 3 kernel to gray scale map gfiAfter noise reduction is carried out, a dual-threshold binarization method is used for setting high and low thresholds t1And t2Then to gf according to formula (1)iBinary image bf is obtained by binarizationi；
Figure BDA0001923441060000031
In the formula, f (x, y) represents the gray value of the pixel point, and the threshold value t1And t2Determining by a valley value of the gray level histogram;
step 2: for binary image bfiUsing Canny operator to obtain its edge image efiAnd edge sets
Figure BDA0001923441060000032
Figure BDA0001923441060000033
Representing edgesiThe jth edge of (1), miRepresenting edgesiThe number of the middle edges is such that,
Figure BDA0001923441060000034
representing edges
Figure BDA0001923441060000035
The k-th pixel point of (1),
Figure BDA0001923441060000036
to represent
Figure BDA0001923441060000037
The corresponding coordinates of the position of the object to be imaged,
Figure BDA0001923441060000038
to represent
Figure BDA0001923441060000039
The total number of pixels in;
and step 3: computing
Figure BDA00019234410600000310
Corresponding closed contour area, is noted
Figure BDA00019234410600000311
If it is
Figure BDA00019234410600000312
And
Figure BDA00019234410600000313
satisfy equation (2), the edge is defined
Figure BDA00019234410600000314
Adding the pressure vessel edge set bottleedges; when all edges meet the requirements
Figure BDA00019234410600000315
When all the parts are added into the pressure container edge set bottleEdges, the parts are marked as bottleEdges { eb ═v|v＝1,2,...,u}，ebvRepresenting the corresponding edge profile of the pressure container, wherein u is the number of the pressure containers in the detection pool;
Figure BDA0001923441060000041
and 4, step 4: if and only if u is not 0, namely a pressure container exists in the water tank, the pressure sensor starts to return the pressure parameter; assuming that u is not 0 in the tightness test of the r th batch, the pressure sequence set of the pressure inside the pressure vessel measured by the pressure sensor is
Figure BDA0001923441060000042
Wherein
Figure BDA0001923441060000043
Is a pressure value, and is a pressure value,
Figure BDA0001923441060000044
is composed of
Figure BDA0001923441060000045
Corresponding acquisition time points, wherein R is acquisition times; if the formula (3) is met, the pressure maintaining time and pressure of the batch of air tightness test are sufficient, the air tightness test is reliable, otherwise, the test is unreliable;
Figure BDA0001923441060000046
wherein, P0Indicating the value of the rated holding pressure value, T0Represents the minimum dwell time required for the gas-tightness test, delta represents the dwell pressure error threshold,
Figure BDA0001923441060000047
indicating a pressure value equal to P in the supercharging stage of the set P0The corresponding collection time point at the time of/2 is recorded as the s-th collection,
Figure BDA0001923441060000048
representing a pressure value equal to P in the decompression phase of the set P0And the corresponding acquisition time point at the time of/2 is recorded as the e-th acquisition.
The invention has the beneficial effects that: the invention can automatically detect the pressure containers and the quantity in the detection pool, when the pressure containers exist in the detection pool, the pressure sensor is used for acquiring the internal pressure value of the pressure container, and further calculating whether the pressure maintaining pressure and the pressure maintaining time of the pressure container reach the rated value according to the pressure value change, thereby avoiding the condition of sub-detection in the air tightness detection.
Drawings
FIG. 1 is an illustration of the mounting positions of a pressure sensor and a camera;
FIG. 2 is a gray scale graph for a gas tightness test;
FIG. 3 is a result of performing dual threshold binarization on an air-tightness test image;
FIG. 4 is an illustration of a pressure curve for a hermeticity test.
Detailed Description
The invention is explained in detail below with reference to examples and figures.
A pressure maintaining detection method for a pressure vessel airtightness test comprises the following specific steps:
step 1: the equipment is installed as shown in figure 1, wherein 1 represents an air pump, 2 represents a pressure sensor, 3 represents a camera, 4 represents a pressure container, 5 represents a detection pool, and 6 represents an air guide pipe; shooting the air tightness test detection pool by an industrial camera, and obtaining a video frame image f from the camera i1,2,.., n, graying fiObtaining a gray image gfiGray scale map gfiAs shown in fig. 2, the 3 x 3 kernel is used for the gray map gfiAfter noise reduction is carried out, a dual-threshold binarization method is used for setting high and low thresholds t1And t2Then to gf according to formula (1)iBinary image bf is obtained by binarizationiBinary image bfiAs shown in fig. 3;
Figure BDA0001923441060000051
in the formula, f (x, y) represents the gray value of the pixel point, and the threshold value t1And t2Determined by the valley of the grey histogram, t in this example1And t2Taking 35 and 50;
step 2: for binary image bfiUsing Canny operator to obtain its edge image efiAnd edge sets
Figure BDA0001923441060000052
Figure BDA0001923441060000053
Representing edgesiThe jth edge of (1), miRepresenting edgesiThe number of the middle edges is such that,
Figure BDA0001923441060000054
representing edges
Figure BDA0001923441060000055
The k-th pixel point of (1),
Figure BDA0001923441060000056
to represent
Figure BDA0001923441060000057
The corresponding coordinates of the position of the object to be imaged,
Figure BDA0001923441060000058
to represent
Figure BDA0001923441060000059
The total number of pixels in;
and step 3: computing
Figure BDA00019234410600000510
Corresponding closed contour area, is noted
Figure BDA00019234410600000511
If it is
Figure BDA00019234410600000512
And
Figure BDA00019234410600000513
satisfy equation (2), the edge is defined
Figure BDA00019234410600000514
Adding the pressure vessel edge set bottleedges; when all edges meet the requirements
Figure BDA00019234410600000515
When all the parts are added into the pressure container edge set bottleEdges, the parts are marked as bottleEdges { eb ═v|v＝1,2,...,u}，ebvRepresenting the corresponding edge profile of the pressure container, wherein u is the number of the pressure containers in the detection pool;
Figure BDA00019234410600000516
and 4, step 4: if and only if u is not 0, namely a pressure container exists in the water tank, the pressure sensor starts to return the pressure parameter; assuming that u is not 0 in the tightness test of the r th batch, the pressure sequence set of the pressure inside the pressure vessel measured by the pressure sensor is
Figure BDA00019234410600000517
Wherein P isi (r)Is a pressure value, and is a pressure value,
Figure BDA00019234410600000518
is Pi (r)Corresponding acquisition time points, wherein R is acquisition times; if the formula (3) is satisfied, the pressure maintaining time and pressure of the batch of air tightness test are sufficient, the air tightness test is reliable, otherwise, the test is unreliable, and the pressure curve diagram is shown in fig. 4;
Figure BDA0001923441060000061
wherein, P0Indicating the value of the rated holding pressure value, T0Represents the minimum dwell time required for the gas-tightness test, delta represents the dwell pressure error threshold,
Figure BDA0001923441060000062
indicating a pressure value equal to P in the supercharging stage of the set P0The corresponding collection time point at the time of/2 is recorded as the s-th collection,
Figure BDA0001923441060000063
representing a pressure value equal to P in the decompression phase of the set P0The corresponding acquisition time point at/2, denoted as the e-th acquisition, in this example, P0、T0And δ values were 30Mpa, 60s and 0.05, respectively.

Claims (1)

1. A pressure maintaining detection method for a pressure vessel airtightness test is characterized by comprising the following steps:
step 1: shooting the air tightness test detection pool by an industrial camera, and obtaining a video frame image f from the camerai1,2,.., n, graying fiObtaining a gray image gfiUsing 3 x 3 kernel to gray scale map gfiAfter noise reduction is carried out, a dual-threshold binarization method is used for setting high and low thresholds t1And t2Then to gf according to formula (1)iBinary image bf is obtained by binarizationi；
Figure FDA0001923441050000011
In the formula, f (x, y) represents the gray value of the pixel point, and the threshold value t1And t2Determining by a valley value of the gray level histogram;
step 2: for binary image bfiUsing Canny operator to obtain its edge image efiAnd edge sets
Figure FDA0001923441050000012
Figure FDA0001923441050000013
Representing edgesiThe jth edge of (1), miRepresenting edgesiThe number of the middle edges is such that,
Figure FDA0001923441050000014
representing edges
Figure FDA0001923441050000015
The k-th pixel point of (1),
Figure FDA0001923441050000016
to represent
Figure FDA0001923441050000017
Corresponding coordinates,
Figure FDA0001923441050000018
To represent
Figure FDA0001923441050000019
The total number of pixels in;
and step 3: computing
Figure FDA00019234410500000110
Corresponding closed contour area, is noted
Figure FDA00019234410500000111
If it is
Figure FDA00019234410500000112
And
Figure FDA00019234410500000113
satisfy equation (2), the edge is defined
Figure FDA00019234410500000114
Adding the pressure vessel edge set bottleedges; when all edges meet the requirements
Figure FDA00019234410500000115
When all the parts are added into the pressure container edge set bottleEdges, the parts are marked as bottleEdges { eb ═v|v＝1,2,...,u}，ebvRepresenting the corresponding edge profile of the pressure container, wherein u is the number of the pressure containers in the detection pool;
Figure FDA00019234410500000116
and 4, step 4: if and only if u is not 0, namely a pressure container exists in the water tank, the pressure sensor starts to return the pressure parameter; assuming that u is not 0 in the tightness test of the r th batch, the pressure sensor measures the pressure sequence set inside the pressure containerAre synthesized into
Figure FDA00019234410500000117
Wherein P isi (r)Is a pressure value, and is a pressure value,
Figure FDA00019234410500000118
is Pi (r)Corresponding acquisition time points, wherein R is acquisition times; if the formula (3) is met, the pressure maintaining time and pressure of the batch of air tightness test are sufficient, the air tightness test is reliable, otherwise, the test is unreliable;
Figure FDA00019234410500000119
wherein, P0Indicating the value of the rated holding pressure value, T0Represents the minimum dwell time required for the gas-tightness test, delta represents the dwell pressure error threshold,
Figure FDA00019234410500000120
indicating a pressure value equal to P in the supercharging stage of the set P0The corresponding collection time point at the time of/2 is recorded as the s-th collection,
Figure FDA00019234410500000121
representing a pressure value equal to P in the decompression phase of the set P0And the corresponding acquisition time point at the time of/2 is recorded as the e-th acquisition.
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