Leak Test Method Research Articles

Comparing Container Closure Integrity Test Methods - Performance of Headspace Carbon Dioxide Analysis versus Helium Leakage Using Positive Controls.

As described in USP Chapter <1207>, the deterministic leak test methods using laser-based gas headspace analysis and helium leakage are those with the highest sensitivities. As stated in the chapter, ″no single package leak test or package seal quality test method is applicable to all product-package systems″; therefore, knowing the advantages and disadvantages of both of these techniques, and the extent to which they can be substituted for each other, is valuable. In an effort to begin addressing this issue, a systematic study using these two techniques has been performed. This study used the same well-defined positive controls prepared with microcapillaries for both measurement techniques. For the headspace gas analysis technique, the headspace carbon dioxide content was measured at multiple timepoints during three separate conditioning cycles using either a 0.5, 1.0, or 2.0 bar CO2 overpressure; the observed change in headspace carbon dioxide was then used to determine an ingress rate for each positive control. For the helium leakage technique, the positive controls were measured with a standard helium leak detector with 100% helium atmosphere on the atmospheric pressure side of the artificial defects. The resulting leakage rates from both techniques were compared for ingress into both ISO 2R and ISO 10R vials. The obtained correlation between helium and carbon dioxide leakage rates resulted in a minimum R2 coefficient of 0.98 across all 12 runs. Additionally, both setups met the acceptance criteria for accuracy with their respective calibrated standards.

Pomegranate freezing tolerance evaluation and its relationship with biochemical parameters

Low temperature is one of the most significant environmental factors that threaten the survival of subtropical and tropical plant species. By conducting a study, which was arranged in a completely randomized design with three replicates, the relative freezing tolerance (FT) of four Iranian pomegranate cultivars, including ‘Alak Torsh’, ‘Tabestaneh Torsh’, ‘Poost Sefid’, and ‘Poost Syah’, as well as its correlation with some biochemical indices, were investigated. From each cultivar, pieces of one-year-old shoot samples were treated with controlled freezing temperatures (−11, −14, and −17 ℃) to determine lethal temperatures (LT50) based on survival percentage, electrolyte leakage, phenolic leakage, and tetrazolium staining test (TST) methods. Results showed that FT was higher in the second year with a lower minimum temperature and a higher concentration of cryoprotectants. The stronger correlation of electrolyte leakage with survival percentage (r = 0.93***) compared to the other three indices explained that this index could be the most reliable injury index in determining the pomegranate FT to investigate freezing effects. Of all four cultivars, ‘Poost Syah’ was the hardest by presenting a higher FT than ~ −14 ℃ in mid-winter. Accordingly, this pomegranate cultivar seems to be promising to grow in regions with a higher risk of freezing and to be involved in breeding programs to develop novel commercial cultivars.

Magnetic Flux Leakage Testing Method for Pipelines with Stress Corrosion Defects Based on Improved Kernel Extreme Learning Machine

This study aims to study the safety of oil and gas pipelines under stress corrosion conditions and grasp the corrosion damage situation timely and accurately. Consequently, a non-destructive testing method combining magnetic flux leakage testing technology and a kernel function extreme learning machine improved by genetic algorithm (GA-KELM) is proposed. Firstly, the variation of the corrosion defect dimension and profile with time is obtained by numerical simulation. At the same time, the distribution of the magnetic flux leakage signal under different defect conditions is analyzed and studied. Finally, feature selection is carried out on the magnetic flux leakage signal distribution curve, and GA-KELM is used to predict the depth and length of corrosion defects so as to realize the non-destructive testing of the pipeline defects. The results show that different geometric features result in different magnetic flux leakage signal distributions. There is a corresponding relationship between the defect dimension and extreme value, area, and peak width of the magnetic flux leakage signal distribution curve. The GA-KELM prediction model can effectively predict the depth and length of corrosion defects, and the prediction accuracy is better than the traditional extreme learning machine prediction model.

On Welding of High-Strength Steels Using Laser Beam Welding and Resistance Spot Weld Bonding with Emphasis on Seam Leak Tightness

The design of most electric vehicles provides for the positioning of the heavy energy storage units in the underbody of the cars. In addition to crash safety, the battery housing has to meet high requirements for gas tightness. In order to test the use of high-strength steels for this sub-assembly, this paper examines welded joints utilizing resistance spot weld bonding and laser remote welding, with special regard to the gas tightness of the welds. For this purpose, the pressure difference test and helium sniffer leak detection are presented and applied. The combination of both leak test methods has proven ideal in experimental investigations. For laser remote welding, gas-tight seams can be achieved with an inter-sheet gap of 0.1 mm, even if occasionally leaking samples cannot be prevented. Resistance spot welding suits gas-tight joining with both one- and two-component adhesives. Against the background of leak tightness, process fluctuations that lead to weld spatter and defects in the adhesive layer must be prevented with high priority.

Optimal design of iron-cored coil sensor in magnetic flux leakage detection of thick-walled steel pipe

Thick-walled steel pipes, which bear high internal pressure, are widely applied in nuclear power and pressure pipelines. If there are defects in the inner wall, they are easy to expand and cause accidents. Therefore, the thick-walled steel pipe must be subject to non-destructive testing after production. For the magnetic flux leakage (MFL) testing method, the detection sensitivity gradually decreases with the increase of wall thickness. To solve this problem, a new structure of MFL probe is proposed in this paper. The influence of the iron core permeability on the MFL signal is analyzed theoretically, and the effect of the core length and diameter on the MFL signal is analyzed by simulation. The variation of the MFL signal with the change of the iron core and coil lift-off is studied respectively. The simulation results are verified by experiments. It is found that the lift-off of the iron-cored coil is determined by the iron core position. Based on this phenomenon, an MFL array probe is designed, which can be used for online detection of thick-walled steel pipes to improve the detection sensitivity of inner wall defects.

Air leakage test system for product without atmosphere air connection

With the air leakage test methods, the leakage tests of the products that are required to be leakproof are carried out. This leakage test starts with placing the product on a fixture. The in-ternal pressure is increased by filling compressed air into the product placed in the Fixture. The product is filled with compressed air up to a previously calculated test pressure value. After the test pressure value is reached for the desired product, the air filling process is completed, and the stabilization period begins. At the end of this period, information about the leakage of the product is obtained, depending on whether there is a change in the internal pressure of the product. In order to fill the product with compressed air, there must be an air hole on the product. Products without this air hole cannot be tested with these methods. With the new method we will develop, it will be possible to test the leakage of closed products without atmosphere-air connection.

Investigation of the leak tightness of structural adhesive joints for use in battery housings considering mechanical and corrosive loads

ABSTRACT Due to increasing legal requirements to reduce emissions from vehicle fleets, vehicle manufacturers are focusing on the electrification of the powertrain. In entirely electrically driven vehicles, the energy is stored in traction batteries integrated below the passenger cell between the axles and thus located in the vehicle’s wet area. Therefore, high requirements apply to the protection of the sensitive cells against mechanical stress as well as against moisture penetration. In addition, one of the main requirements for the connections of the battery housing is to ensure gas tightness over the entire service life. Adhesive bonding technology as a planar joining process offers the potential to produce functionally tight connections. However, there is a lack of reliable test methods for validating the long-term tightness of structural adhesive joints under mechanical and corrosive loads. For this reason, the paper deals with developing a test concept with laboratory-scale test specimens for leak testing under mechanical loading. Various leakage test methods investigate the leakage rate of structurally bonded joints. An analysis of the leakage rate under superimposed cyclic mechanical shear tensile loading follows this. The test method is validated on a specially developed sample battery housing on a laboratory scale.

Feasibility study of using the magnetic flux leakage test method in detecting defects in the coating of supply and distribution gas lines

امروزه پدیده خوردگی خطوط تغذیه و توزیع نفت و گاز چالشی اساسی در این صنایع است. برای جلوگیری از خوردگی لوله های مدفون زیر خاک از انواع پوشش ها بخصوص پوششهای پایه قیری برای محافطت از خطوط لوله نفت و گاز استفاده می شود. یکی از تست های پر کاربرد برای تشخیص عیوب لوله های فلزی خطوط انتقال گاز روش تست نشت شار مغناطیسی می باشد . این تست فقط روی خود لوله فلزی انجام می شود و عیوب لوله را مشخص می کند . در این مقاله ، امکان استفاده از این تست برای تشخیص عیوب پوشش خطوط لوله بررسی شده است. در صورت تشخیص عیوب پوشش میتوان از گسترش و رسیدن آنها به بدنه فلزی لوله جلوگیری کرد. بدین منظور تست نشت شار مغناطیسی قسمتی از لوله گاز به همراه پوشش قیر پایه ذغال سنگی به همراه یک عیب و با ضخامت های مختلف در لوله و پوشش، در نرم افزار کامسول شبیه سازی شد . خواص مغناطیسی پوشش نیز با دستگاه مغناطیس سنج استخراج شد. نتایج شبیه سازی ها نشان دادند که نشت شار مغناطیسی در عیوب پوشش ناچیز بوده و برای آشکار سازی عیوب قابل اندازه گیری نیست.

Hydrostatic Penetration Testing of Protective Glove Materials Using Water and Synthetic Blood to Evaluate Hole Size and Screen Mesh Using an Automated Pressure Delivery System.

There are several international standards that address the resistance of chemical protective clothing materials to the penetration by liquids. The hydrostatic pressure has been documented to discriminate between protective clothing material performance and correlates with visual penetration results that are obtained with human factors validation. The same methodology, based on hydrostatic pressure equipment, is referenced also in other standards addressing penetration resistance of protective clothing and glove materials against synthetic blood or blood-borne pathogens. In this study, we present an automated hydrostatic penetration testing that integrates testing procedures from several standards to evaluate the resistance of materials to penetration by liquids under pressure. The automated control system allows the user to select a specific test method and automatically sets a stepped pressurization protocol to test the material. A pass or a fail result is produced at a certain time and pressure. As an example of application, the penetration of synthetic blood was assessed through gloves made from different materials with ISO 16603, method B, one of the five possible penetration methods and protocols available in the test equipment. The results indicate that the developed system facilitates the application of test methods used to evaluate the barrier effectiveness against liquids of materials used for protective clothing and gloves and show up that the characteristics of the retention grid used have a decisive influence on the test results. In some of the tested glove materials, holes were intentionally performed with needles with different gauges. The capacity of pinhole detection in gloves was evaluated according to the test method selected and compared with results obtained with the classic water leak test method for gloves described in EN ISO 374-2.

Design, optimization and test of RHMB considering dynamic characteristics

The coil inductance, stiffness and losses of the magnetic bearing (MB) have great influence on the dynamic performance for the magnetically suspended control moment gyro (MSCMG) application. Based on the equivalent magnetic circuits considering flux leakage effects, a design, optimization and test method is proposed to enhance the dynamic response ability for the radial hybrid MB (RHMB). The optimization design objectives including bearing force, stiffness, coil current, mass, inductance and loss estimation are discussed under the multiple constraints. Compared with the original design, the dynamic characteristics including frequency responses of current and rotor displacements for the RHMB-rotor system are significantly improved after optimization. A prototype of MSCMG is fabricated to verify the dynamic response characteristic of the RHMB.

Development of a low-cost device for testing glove and condom leakage

BackgroundCurrently, hospital-acquired infections in healthcare workers and patients are a major concern. On the other hand, sexually transmitted infections and diseases, unwanted pregnancies, and unsafe abortions continue to be a public health concern, particularly in developing countries. Gloves are among the most commonly used personal protective equipment to safeguard healthcare workers' hands from contagious infections, and using a condom is strongly advised for people who have sexual relations with more than one partner. However, the quality of gloves and condoms in developing countries is a subject of concern. The usage of quality test instruments such as glove leakage test apparatus (GLTA), leakage testers by water level, the Ammonia leak testing method (ALTM), conductivity-based leakage testers, and water hang testers in developing countries is limited owing to cost, accessibility, and safety. The main purpose of this study was to develop and test a low-cost integrated device to test glove and condom leakage that is safe and easily accessible in resource poor settings. MethodIn this study, an integrated glove and condom leakage testing device for detecting pin holes and leakages is proposed. The device automatically fills a randomly selected condom and glove with a predetermined volume of water based on International Organization for Standardization (ISO) criteria. ResultsThe prototype of the proposed device was successfully developed and tested. The accuracy of 98.66% for filling condom samples with 300 ml of water and 99.29% for filling glove samples with 1000 ml of water was achieved. ConclusionThe implementation of the developed prototype in resource poor settings to test gloves and condom leakage has the potential to improve the safety of healthcare workers, patients, and the general public.

Evaluation of defect depth in ferromagnetic materials via magnetic flux leakage method with a double Hall sensor

In the magnetic flux leakage (MFL) testing method, a linear mapping is used for the direct evaluation of defects by applying a single Hall sensor to measure the signal under a certain lift-off value. Inevitably, the uncertainty of the lift-off value in practical testing affects the accuracy of the estimated defect size. To overcome this uncertainty in the lift-off value, this paper proposes a double Hall sensor configuration with a fixed lift-off interval, and establishes an evaluation method for the defect depth through the MFL signals measured by this sensor. The effectiveness of the proposed evaluation method is verified by theoretical analysis, with the double Hall sensor providing two different lift-off values above the surface of the specimen that characterize the tested defect. Based on the error between the measured signal characteristics induced by the tested defect and the predicted values from a fast calculation model, a particle swarm optimization algorithm is employed to realize accurate evaluation of the defect depth. Theoretical research shows that the characteristic values measured by the double Hall sensor enable the defect depth to be accurately estimated. The use of a double Hall sensor with a fixed lift-off interval allows the proposed evaluation method to compensate for the unknown lift-off value in practical testing.

Investigation of evaluation method for wire rope breakages by magnetic flux leakage testing

Inspection using magnetic sensors based on the magnetic flux leakage testing method as soundness evaluation of wire ropes is being performed. Recently, it has been studied as detailed soundness evaluation method of the wire rope by analyzing the measurement data of multi magnetic sensors as an image grayscale. However, this is the position identification of breakages rope axis direction. For this reason, if it is not the position identification of breakages on the rope circumferential direction, it is difficult to determine soundness evaluation of wire ropes. In this study, there are three characteristics (types (crown and valley), number of wire breakages, the distance between detection plane and wire rope surface) of the breakage. In this paper, the magnetic flux density of the wire rope caused by the number of breakages is examined using numerical analysis.

Laboratory investigations on the quality of leak tests and visual inspections of wastewater connection pipes carried out by specialist contractors

Abstract In addition to stability and operational safety, leak tightness is the permanent functional objective of wastewater pipes. Tests to determine the tightness of wastewater pipes can in some cases produce results that are worthy of discussion. Therefore, laboratory tests were carried out by 29 specialist contractors to obtain results on the quality of leak tests and visual inspections of connection pipes. The results showed that different test errors can be observed for leak test methods (air overpressure, air underpressure and water pressure). However, only in the case of the water pressure tests did the observed test errors occasionally lead to incorrect test results, i.e. the ‘leaking pipe’ was tested as ‘test passed (tight)’. The investigations into the accuracy (trueness and precision) of the test methods showed that all test methods examined were sufficiently accurate to determine the tightness of the connection pipes. In general, correct test results were achieved if the expert testers did not make any serious test errors and the test equipment used functioned properly. In contrast, the investigations on the quality of visual inspection showed that the procedure is not sufficiently reliable to fulfil all normative requirements regarding damage detection and naming as well as damage classification.

Evaluation of testing procedures for real-scale sewage pipes

AbstractTests to determine the tightness of wastewater pipes can in some cases produce results that are worthy of discussion. Therefore, testing procedures for real-scale sewage pipes used for house connections were evaluated and data were statistically analysed. The results of the investigation showed that leaky pipes are detected with a very high degree of reliability by all leak test methods. The test methods are also robust against errors by expert testers and deviations from the test specifications. In contrast, tight pipelines can also be incorrectly classified as ‘leaking’ (test failed) to a significant extent during leak tests. Even for the more reliable test methods, i.e. air overpressure, air underpressure and water with low test pressure, a tight pipe is incorrectly classified as leaking (false positive) in one out of 10 cases (10%). The highest false-positive rate was 20% for water with high test pressure. In addition to the leak test methods, the quality of the visual inspection was also analysed. Here it was found that visual inspection is not sufficiently reliable for determining the tightness of pipelines above the groundwater level. Error rates of approximately 50% were found for the detection of tight and leaky pipelines.

Leak Performance

Leak testing methods are becoming increasingly sophisticated as manufacturers try to keep up with demand for more waterproof consumer devices

Spacecraft hatch leak testing

Spacecraft hatch needs to be tested for leakage in various environments. Hatch Quick Leak Detector (HQLD) leak testing method is a convenient and effective method for the orbital hatch. Vacuum Chamber leak testing (VCLT) method is a proper integral leakage rate method for the hatch. We performed the testing in the “CMK2000” vacuum vessel. The detection principles and steps are described in detail. Leak testing was performed on all of the hatch seals using helium mass spectrometer leak detectors and special apparatus under the Thermal Vacuum testing. We performed leak testing after finishing operating the hatch in the Thermal Vacuum environment. The relative uncertainty of the total leakage rate value of the hatch is 23.6% (k = 2). The total leakage rate testing was a successful example of complex quantitative leakage rate testing in a middle vacuum chamber.

Does intraoperative flexible endoscopy offer any benefit compared to conventional air leak testing after circular stapled left-sided laparoscopic colon surgery?

Anastomotic leakage is still a feared complication after left-sided colonic resections. Various types of "anastomotic leak testing methods" are described in current literature. In this study we evaluated the use of intraoperative flexible endoscopy in comparison to conventional air leak testing after performing a circular stapled anastomosis in left-sided laparoscopic colon surgery. A retrospective database consisting of 130 patients with left sided colonic resections between 01/2015 and 12/2019 at our hospital was evaluated. After performing a circular stapled anastomosis flexible endoscopy was done in 69 cases, 61 patients were controlled with a conventional air leak test. Intraoperative and postoperative complications were recorded and retrospectively evaluated. In the flexible endoscopy group, we observed complications in 13,04%, in the conventional air leak testing group in 9.83%. Postoperative anastomotic leakage was observed in 10,14% in the flexible endoscopy group and 4.91% in the conventional air leak test group. In 10.14% a positive air leak test was seen in the flexible endoscopy group and 11.47% in the conventional air leak testing group. In those cases, we observed no postoperative complications in the first group, in the conventional group we had two anastomotic leakages and one infected haematoma. In the case of a positive air leak, flexible endoscopy offered a more exact detection of the leak. In those cases, no anastomotic leakage was observed postoperatively. In our opinion, flexible endoscopy should be recommended for testing the anastomosis intraoperatively in every left-sided colon surgery.

A numerical simulation method of nonlinear magnetic flux leakage testing signals for nondestructive evaluation of plastic deformation in a ferromagnetic material

Nonlinear Magnetic Flux Leakage Testing (MFLT) method is a relative new non-destructive testing (NDT) technique for inspection defect or micro damage in structure of ferromagnetic material by measuring the leakage magnetic field during an alternative magnetization process. To enhance the nonlinear MFLT technique, a numerical tool for simulating the inspection signal is very important in views to clarify the detection mechanism and to improve the detection efficiency. However, most of the simulation methods on magnetic NDT problems solve problem without considering the hysteresis effects of ferromagnetic materials and is difficult to deal with the influence of mechanical damage. In this paper, a numerical scheme is proposed at first to simulate the nonlinear MFLT signals considering the nonlinearity and hysteresis characteristics of ferromagnetic materials based on the equivalent magnetic polarization approach and FEM-BEM hybrid method. The validities of the proposed method and the corresponding numerical code are proved by comparing the simulation results of a typical nonlinear MFLT problem with the experimental measured signals. Secondly, in order to cope with the influence of plastic deformation in material on the nonlinear MFLT signals, a magneto-mechanical coupling constitutive relation is proposed and applied to the developed numerical simulation code. Finally, the nonlinear MFLT signals of specimen with different plastic deformation are simulated with the developed numerical code and the influence mechanism of plastic deformation on nonlinear MFLT signals is discussed based on the numerical results. The results reveal that the distortion of nonlinear MFLT signals mainly due to the magnetic remanence coefficient of material which can be significantly influenced by micro damage such as the plastic deformation.

Comparison of the Aerosol Photometer and Light Scattering Airborne Particle Counter (LSAPC) Methods for Installed Filter System Leak Testing

Abstract The installed filter system leak test method for cleanrooms and clean zones is described in ISO 14644-3, Cleanrooms and associated controlled environments—Part 3: Test method. Portions of the methods in ISO 14644-3 were adapted from IEST-RP-CC034.4[Schaumburg, Illinois, US: Institute of Environmental Science and Technology], which provides a set of recommended procedures for leak testing HEPA and ULPA filters in situ (in the field) with the aerosol photometer test method and the light scattering airborne particle counter (LSAPC) test method. Leak testing is performed to confirm that the final high efficiency air filter system is properly installed by verifying the absence of bypass leakage in the installation, and that the filters are free of defects (small holes and other damage in the filter medium, frame, seal and leaks in the filter bank framework). This study was conducted to compare the aerosol photometer and LSAPC methods. Testing in the study consisted of creating artificial leaks in the filter system, measuring the upstream and downstream concentrations with the aerosol photometer and with the LSAPC, and comparing the filter leak penetration results. Comparison testing was applied to the procedure for the installed terminal panel filter system leakage scan test (stationary measurement) and the procedure for evaluating overall leakage of high-airflow box-type filters mounted in a duct or air-handling unit (AHU) (overall leakage test). It was found that the aerosol photometer and the LSAPC gave similar results for filter leakage within experimental error. The comparison of the leakage scan tests (stationary measurement) showed that the penetration calculated for the channel ≥ 0.3 μm of the LSAPC with an air flow rate of 1cu ft/min (CFM) (28.3 l/min) was very similar to the penetration measured with the aerosol photometer for a leakage level &amp;gt;0.01 % of the upstream concentration. The comparison result of the overall leakage test showed that overall total penetration values, obtained after dilution of artificial calibrated leaks in the filter media, were identical, within the measurement uncertainty, for particles ≥0.3 μm whether the sampling rate of the LSAPC was 1 CFM (28.3 l/min) or 50 l/min. Several recommendations are provided. In particular, for filters mounted in a duct or AHU where the filter function is critical, the recommended method is the leakage scan test method, using a grid sampling method in a plane downstream of the filter (as agreed between customer and supplier).