Leak Test Method Research Articles

Comparison and analysis of multiple signal processing methods in steel wire rope defect detection by hall sensor

Steel wire rope (SWR) defect signal processing techniques and methods are the key to exact defect detection and identification, which is important in guaranteeing human lives and property. But the inspection signals sensed by the commonly used inductive coil sensor are often susceptible to the detector’s scanning speed, wire rope shaking and vibration, whereas they are unaffected when induced by hall element sensor. Thus, the experiments for wire rope local fault (LF) of broken wire inspection by hall sensors and magnetic flux leakage (MFL) testing method are conducted, and different groups of original signals are obtained. Then, performances of multiple signal processing methods are compared and evaluated in the perspective of baseline drift elimination and signal denoising. Besides, the main impact parameters in these signal processing methods are investigated and revealed. Finally, comparisons and discussions for different filtering methods are analyzed and presented.

A Novel Magnetic Flux Leakage Testing Method Based on AC and DC Composite Magnetization

The flexible printed coil array (FPC) is employed extensively because of its flexibility in non-destructive testing (NDT). To make the inductive coil detect both external and internal defects under static conditions in magnetic flux leakage testing (MFL), this paper proposes a method based on the AC and DC composite magnetization. The AC magnetization changes the magnetic field strength in the vicinity of external defects. The DC magnetization makes the defects generate static leakage magnetic field. The permeability in the skin layer is also altered by the AC magnetization which affects the transmission of leakage magnetic field caused by internal defects. Therefore, external and internal defects can generate a time-varying leakage magnetic field. Simulations and experiments are carried out to validate the feasibility of this method. The results indicate that the method based on the AC and DC composite magnetization can be applied to detect both external and internal defects.

A Chip Integrity Monitor for Evaluating Moisture/Ion Ingress in mm-Sized Single-Chip Implants

For mm-sized implants incorporating silicon integrated circuits, ensuring lifetime operation of the chip within the corrosive environment of the body still remains a critical challenge. For the chip's packaging, various polymeric and thin ceramic coatings have been reported, demonstrating high biocompatibility and barrier properties. Yet, for the evaluation of the packaging and lifetime prediction, the conventional helium leak test method can no longer be applied due to the mm-size of such implants. Alternatively, accelerated soak studies are typically used instead. For such studies, early detection of moisture/ion ingress using an in-situ platform may result in a better prediction of lifetime functionality. In this work, we have developed such a platform on a CMOS chip. Ingress of moisture/ions would result in changes in the resistance of the interlayer dielectrics (ILD) used within the chip and can be tracked using the proposed system, which consists of a sensing array and an on-chip measurement engine. The measurement system uses a novel charge/discharge based time-mode resistance sensor that can be implemented using simple yet highly robust circuitry. The sensor array is implemented together with the measurement engine in a standard 0.18 μm 6-metal CMOS process. The platform was validated through a series of dry and wet measurements. The system can measure the ILD resistance with values of up to 0.504peta-ohms, with controllable measurement steps that can be as low as 0.8M Ω. The system works with a supply voltage of 1.8V, and consumes 4.78mA. Wet measurements in saline demonstrated the sensitivity of the platform in detecting moisture/ion ingress. Such a platform could be used both in accelerated soak studies and during the implant's life-time for monitoring the integrity of the chip's packaging.

Prevalence and associated factors of surgical gloves perforation in elective orthopaedic and trauma surgeries done at KCMC, from November 2018 through May 2019; Prospective observational study

Background: Since medical history and examination can’t reliably identify all patient harbouring blood-borne pathogens, universal precautions during exposure to blood and body fluid are now imperative. Intact surgical glove is an integral part aimed to protect patients from the surgical team members’ microbial flora of the hand and mutually, surgical team members from pathogens of the patient’s body, nevertheless surgical glove perforation is a major concern with a perforation rate as high as 50% has been reported in literature depending on the type of surgery. The risk of perforation is thought to correlates with many factors, yet very few prospective studies have addressed this issue at Kilimanjaro Christian Medical centre Hospital. Objective: The intent of this study was to determine the prevalence and associated factors of surgical gloves perforation in elective orthopaedic and Trauma surgeries. Methods: Prospective observational study design was conducted at Orthopaedics and Trauma operating theatres. Systematic sampling technique was used, after surgery inner and outer surgical gloves utilized by the surgical team were collected, labelled and tested by water leak test method (EN 455-1) consisting of visual evaluation of gloves after hydro insufflation. Results: Total of 1672 surgical gloves were collected during the study period, overall perforations were found to be 17.1%, higher perforation seen in bone surgeries. Among the surgical team members, the highest perforation was seen in surgeons 49.7% with much involvement of index finger 36.9% followed by the thumb 21.1% in the non-dominant hand. Surgeries lasting longer than 90 minutes found to associate with a high proportion of surgical glove perforation. Conclusion: Our results portray that there is a significant relationship between the type of surgery, the role of surgical a team member, the dominance of the hand, glove layer and the location of perforation with the prevalence of surgical glove perforation.

Towards CMOS Bulk Sensing for In-Situ Evaluation of ALD Coatings for Millimeter Sized Implants.

To meet the dimensional requirements for bioelectronic medicine, new packaging solutions are needed that could enable small, light-weight and flexible implants. For protecting the implantable electronics against biofluids, recently various atomic layer deposited (ALD) coatings have been proposed with high barrier properties. Before implantation, however, the protective coating should be evaluated for any defects which could otherwise lead to leakage and device failure. In these cases, the conventional helium leak test method can no longer be used due to the millimeter size of the implant. Therefore, an in-situ sensing platform is needed that could evaluate the coating and justify the implantation of the final device. In this work, we explore the possibility of using the CMOS bulk for such a platform. Towards this aim, as a proof of concept, test chips were made in a standard 6-metal 0.18 µm CMOS process and for the connection to the bulk, a p+ diffusion was used. A group of samples was then coated with an ALD multilayer. For coating evaluation, off-chip DC current leakage and impedance measurements were carried out in saline between the CMOS bulk and a platinum reference electrode. Results were compared between non-coated and coated chips that clearly demonstrated the potential of using the bulk as a sensing platform for coating evaluations. This novel approach could pave the way towards an all integrated in-situ hermeticity test, currently missing in mm-size implants.

Lack of tightness analysis of concealed welded radiators

Stainless steel X2CrNi18-9 (304L) radiators were analysed. During detailed examination we proved that tube overlap fillet joint was welded incorrectly and had leaks. Wrong designed jig, incorrect robot movements and non-central tubes position let mounted parts move during welding operation. Shrinkage of the weld caused the tubes to move relative to each other with the formation of a larger gap on one side. Lack of correction of the robot arm movement and fixed stick-out created inadequate fusion into the tube with a smaller cross-section.Identification of non-compliance based on standard NDT methods such as visual inspection, liquid or dye penetrant inspection or X-ray was not possible. Also, destructive methods such as high-pressure water test was not be able to show this type of defect.Only innovative HLT helium leak testing method was able to show non-compliance of the joint. Helium is the ideal element to detect micro cracks in weld as it is an insert gas made up to tiny atoms and has low viscosity, so little atoms can travel fast. This method has a very big potential in the welding industry as a precise and fast NDT test on highest quality requirements.

Industrial leak testing of dangerous goods packagings

The Dangerous Goods Regulations currently do not include limit leakage rates or sensitivity requirements for industrial leak testing procedures that are equivalent to the bubble test, which is the prescribed test method for design type testing of dangerous goods packagings. During series production of such packagings, various methods are used, which often do not meet the requirements of the bubble test with regard to important criteria.Sensitivity, flow direction, pressure level and automatability are particularly important factors when selecting a suitable industrial leak testing method.The following methods are in principle both suitable and equally effective as the bubble test: pressure rise test (vacuum chamber), ultrasonic bubble leak detection and gas detection methods (pressure technique by accumulation and vacuum chamber technique).To ensure a uniform test level during design type testing and production line leak testing and therefore a comparable safety level as required by the Dangerous Goods Regulations, it is necessary to include a more precise specification in these regulations. This requires, on the one hand, information about the sensitivity of the bubble test and, on the other hand, the inclusion of a list of suitable, equally effective industrial test methods with their specific boundary conditions.

Theory and Application of the Internal Leakage Detection of Open-Circuit Hydraulic Systems Based on Active Hydraulic Test Technology

Abstract With the rapid development of hydraulic technology, hydraulic systems have become more complex, and the detection of internal leakage is becoming more and more difficult. A fast and accurate approach is required to detect the internal leakage of a hydraulic system. This article describes the theory and application of the internal leakage detection of open-circuit hydraulic systems based on Active Hydraulic Test Technology. The theory of Active Hydraulic Test Technology is introduced, a leakage model and an online detection model of an open-circuit hydraulic system are established, and the total leakage of the hydraulic system is theoretically analyzed. A theoretical analysis of the leakage test method for the main control oil circuit and branch components is also conducted. Through applied research on a hydraulic system of a 1,250-ton forging machine, the effectiveness of the method for detecting the internal leakage fault of a complex hydraulic system is verified.

Multifunctional Emergency Plugging Test and Simulation Training Method

This research involves multifunctional belt pressure emergency leak test and simulation training methods, through a lot of water pressure test, Flow meter, pressure transmitter, liquid level meter, inverter and other effective flow, pressure, liquid level sensors, motor frequency data, to provide emergency leak test and simulation training scientific reference data and theoretical basis.

Gas System for the ATLAS NSW Micromegas Detectors: Design Aspects and Advanced Validation Methods for their QA/QC

In this work we present the design aspects of the Gas Distribution System of NSW Micromegas detectors, simulation results and gas flow / pressure uniformity. We also describe the appropriate gas leak test methods, a conventional and an alternative one, being used in the Quality Assurance and Quality Control of the detectors. For the performance studies we used emulated leak branches based on medical needles. We also describe proposed upgrade stages combining the proposed competitive Flow Rate Loss method with the Lock-in Amplifier technique. Further, we describe the baseline setup for the Gas Tightness Station at BB5/CERN.

Leakproofness of dangerous goods packagings—comparison of worst‐case limit leakage rates and sensitivity of the bubble test

This work focuses on the question if the bubble test prescribed in the Dangerous Goods Regulations has sufficient sensitivity to detect leakage rates, which could result in the formation of explosive atmospheres during transport. The sensitivity of the bubble test is not directly comparable with other leak testing methods because of its different flow conditions. Therefore, a normalized minimum detectable leakage rate under Helium test conditions is calculated for the bubble test. This sensitivity of the bubble test under reference conditions is compared with limit leakage rates for a worst‐case transport scenario. The sensitivity of the bubble test is not sufficient to prove the limit leakage rates for 6‐L packagings. The formation of explosive vapour‐air‐mixtures cannot be excluded. Therefore, more sensitive leak testing methods should be considered for smaller packaging design types.

Container Closure Integrity Testing-Method Development for Freeze-Dried Products Using Laser-Based Headspace Oxygen Analysis.

The regulatory expectations introduced by the U.S. Food and Drug Administration in 1999, ICH Q5C, the revised draft of Annex 1, Eudralex volume 4 for consultation, and the recent update of USP general chapters 1207.1 and 1207.2 regarding container closure integrity (CCI) testing have created a need for further development of testing methods, although there are no universally accepted methods to test and evaluate the CCI of a biopharmaceutical drug product. Each testing method and principle has merits and demerits.This paper will present a simple approach to be used in method validation of CCI testing based on headspace oxygen analysis for freeze-dried biopharmaceutical drug products in vials, as well as a method for testing and verifying positive control vials. The model is based on Fick's law of diffusion and is empirically corrected to account for Knudsen diffusion in smaller defect sizes. The model considers storage conditions of the vials, allowing for testing of vials stored under anaerobic and near-sealing pressure conditions and different temperature conditions, as well as testing at different time points. Using this approach based on headspace oxygen analysis, the minimum timeframe for leak detection is dependent on the volume of the object tested, but standard vial sizes have shown that leak sizes of 0.2 μm can be detected within hours of vial stoppering with the model developed. CCI testing by headspace oxygen analysis using this approach can be done quickly and non-destructively. This method can prove its effectiveness in demonstration of a protective critical barrier (CCI) for a biopharmaceutical drug product during real-time situations of manufacturing, transportation, registered storage conditions, etc. (life-cycle approach).LAY ABSTRACT: The recent update of the guideline, USP general chapters 1207.1 and 1207.2, regarding container closure integrity (CCI) testing, has created a need for further development of testing methods. The new methods applied should be deterministic, i.e., describe predefined detection limits and objective quantitative data. Deterministic leak test methods are methods for which the leakage event being detected or measured is based on phenomena that follow a predictable chain of events.At present, there is no universally accepted method to test and evaluate the CCI of a biopharmaceutical drug product.This paper will present a simple model-based method based on headspace oxygen analysis for freeze-dried biopharmaceutical drug products in vials, as well as a method for testing and verifying positive control vials. Positive controls are vials with a known defect, e.g., an inserted micropipette.The model considers storage conditions of the vials, allowing for testing of vials stored under different pressure and temperature conditions, as well as testing at different time points. CCI testing by headspace oxygen analysis using the new approach can be done quickly and without destruction of the vials. This method can prove its effectiveness in demonstration of a protective critical barrier (CCI) for a biopharmaceutical drug product during real situations of manufacturing, transportation, registered storage conditions, etc.

Reinforcement of the Staple Line during Gastric Sleeve: A Comparison of Buttressing or Oversewing, versus No Reinforcement- A Single-Institution Study

Laparoscopic sleeve gastrectomy (LSG) is a well-established treatment for morbid obesity. Staple line leak (SLL) remains one of the most serious and life-threatening complications after LSG; however, no consensus exists for prevention. The purpose of this study is to review and compare the different methods of staple line management used at our institution. Retrospective review of preoperative, intraoperative, and postoperative factors was performed for all patients undergoing LSG at a single institution between September 2010 and August 2015. Primary outcome measure was SLL by reinforcement method (none/Seamguard/Oversewing). A total of 256 patients undergoing LSG were included, 197 (76.95%) were women and 233 (87.11%) were whites. The patients had a mean age of 44.64 years and body mass index of 49.24 kg/m-2. Among those patients, 145 (56.64%) had staple line reinforced with suture (28, 10.94%) or Gore Seamguard (115, 44.92%) and 111 (43.36%) had no reinforcement, with no difference in baseline factors between the groups (all P > 0.05). Gastric leaks were identified in nine patients (3.52%) with no difference between reinforcement (2.7 vs 2.1%, P = 0.54) or leak test method (air vs methylene blue). However, oversewing the staple line was associated with higher incidence of stenosis (P < 0.01). SLL after LSG is a serious complication with significant morbidity and mortality. This study demonstrated that staple line reinforcement does not provide significant leak reduction but does reduce intraoperative staple line bleeding. In addition, oversewing the staple line was associated with postoperative sleeve stenosis without added benefits.

Alternating Current Electric Flux Leakage Testing for Defect Detection and Characterization

This paper analyzes the inspection characteristics of the alternating current electric flux leakage (AC-EFL) testing method. Three specimens with different conductivity are prepared, and a series of experiments is carried out to explore the advantages and disadvantages of the AC-EFL method. For metal materials that carry an alternating current (AC), defect detection can be realized using both AC-EFL and electric current perturbation (ECP). However, the signal noise ratio (SNR) from using the AC-EFL method is lower than that obtained using the ECP method according to the experimental results obtained from an aluminum plate. For both the Ni–Zn ferrite specimens with very low conductivity and the carbon fiber reinforced polymer (CFRP) specimens with low anisotropic conductivity, the ECP method failed to detect defects because of the weak disturbed magnetic field that was caused by the defects, whereas the AC-EFL method was able to realize the defect detection. These proof-of-concept experimental results indicate that compared to magnetic field testing method, the AC-EFL is more suitable for inspecting low-conductivity materials.

NON-PARAMETRIC ALGORITHM FOR CONSTRUCTING CLASSIFICATION STRUCTURE OF THE LEAKAGE TEST CHARACTERISTICS

The problems of correct and effective choice of the methods and means used for leakage monitoring by penetrating substances (gases) on the basis of certain criteria are considered. Methods of mathematical statistics are used for classification analysis of the main characteristics of the leakage test methods and approaches in the framework of general theoretical research to prioritize them in compliance with current GOST 51780–2001. In other words, an attempt has been made to search for and identify the effective ways of ordering the classification structure from the main characteristics of the methods and means of leak testing necessary for the researcher at the preparatory stage of testing. This is partly due to the lack of clear recommendations in this standard regarding the significance of these characteristics for leakage control in real conditions and possibility of its implementation. The procedure rests on the proposed nonparametric algorithm which includes classification of the characteristics based on pairwise clustering. The expert evaluation method is used for effective addressing the problem of nonparametric analysis. Solutions of multivariate analysis are given for the problem of inverse reduction of characteristics to a small number of groups formed on the basis of generalizing features using discriminative analysis on the basis of nonparametric criteria to check statistically significant difference. Comparatively high posterior probability of attributing the classification features to the groups distributed among six clusters is determined as a result of studying characteristics pertaining mainly to the leakage test facilities (as the most numerous ones compared to test methods). We also consider and assess the possibility of introducing some clarifications to refine the current standard.

Selection Considerations for your Optimum Leak Testing Method and Process

SummaryLeak testing with air or tracer gas has made significant progress in the last decade with respect to technology, improved sensitivity and shorter cycle times. The motivation was driven by stricter environmental regulations and cost pressure. The article gives an overview of different leak testing methods. Furthermore a question guideline for the selection of the optimal leak detection method for different applications is introduced.

A Lift-Off-Tolerant Magnetic Flux Leakage Testing Method for Drill Pipes at Wellhead.

To meet the great needs for MFL (magnetic flux leakage) inspection of drill pipes at wellheads, a lift-off-tolerant MFL testing method is proposed and investigated in this paper. Firstly, a Helmholtz coil magnetization method and the whole MFL testing scheme are proposed. Then, based on the magnetic field focusing effect of ferrite cores, a lift-off-tolerant MFL sensor is developed and tested. It shows high sensitivity at a lift-off distance of 5.0 mm. Further, the follow-up high repeatability MFL probing system is designed and manufactured, which was embedded with the developed sensors. It can track the swing movement of drill pipes and allow the pipe ends to pass smoothly. Finally, the developed system is employed in a drilling field for drill pipe inspection. Test results show that the proposed method can fulfill the requirements for drill pipe inspection at wellheads, which is of great importance in drill pipe safety.

Ultrasound assessment of subglottic region for estimation of appropriate endotracheal tube size in pediatric anesthesia.

Background and Aims:Endotracheal tube (ETT) selection in pediatric patients is mainly done with the age, height, or weight-based formula. We compared ultrasound assessment of the subglottic area to predict the outer diameter of the ETT, with that of modified Cole's formula. The aim of the study is to compare the appropriateness of uncuffed ETT selection based on modified Cole's formula with that of ultrasound assessment method of subglottic diameter in children undergoing surgical procedures under general anesthesia.Material and Methods:This is a prospective, randomized, parallel group study. One hundred and fifty American Society of Anesthesiologists I and II patients of age 2–6 years were randomly allotted into two groups: Group A - ETT selection based on ultrasound assessment of subglottic diameter. Group B - ETT selection based on modified Cole's formula. The study parameters are the internal diameter and external diameter (OD) of the predicted ETT by the two methods and that of the appropriate size ETT used.Results:The incidence of appropriate tube selection was 74.7% in the ultrasound based group while it was 45.3% in the modified Cole's formula group. There was a strong correlation between OD of the optimal ETT used and the ultrasound assessed subglottic diameter. Bland–Altman analysis of OD of appropriately sized ETT and subglottic diameter by ultrasound assessment has a bias of 0.02 mm with limits of agreement of +1.78 to −1.74.Conclusion:Ultrasonographic assessment of the subglottic diameter at the cricoid region is a better tool in predicting the appropriate size uncuffed ETT than modified Cole's formula.

Method Development for Container Closure Integrity Evaluation via Headspace Gas Ingress by Using Frequency Modulation Spectroscopy.

USP <1207.1> Section 3.5 states that "A deterministic leak test method having the ability to detect leaks at the product's maximum allowable leakage limit is preferred when establishing the inherent integrity of a container-closure system." Ideally, container closure integrity of parenteral packaging would be evaluated by measuring a physical property that is sensitive to the presence of any package defect that breaches package integrity by increasing its leakage above its maximum allowable leakage limit. The primary goals of the work presented herein were to demonstrate the viability of the nondestructive, deterministic method known as laser-based gas headspace analysis for evaluating container closure integrity and to provide a physical model for predicting leak rates for a variety of container volumes, headspace conditions, and defect sizes. The results demonstrate that laser-based headspace analysis provides sensitive, accurate, and reproducible measurements of the gas ingress into glass vial-stopper package assemblies that are under either diffusive or effusive leak conditions. Two different types of positive controls were examined. First, laser-drilled micro-holes in thin metal disks that were crimped on top of 15R glass vials served as positive controls with a well-characterized defect geometry. For these, a strong correlation was observed between the measured ingress parameter and the size of the defect for both diffusive and effusive conditions. Second, laser-drilled holes in the wall of glass vials served as controls that more closely simulate real-world defects. Due to their complex defect geometries, their diffusive and effusive ingress parameters did not necessarily correlate; this is an important observation that has significant implications for standardizing the characterization of container defects. Regardless, laser-based headspace analysis could readily differentiate positive and negative controls for all leak conditions, and the results provide a guide for method development of container closure integrity tests.LAY ABSTRACT: The new USP 39 <1207>, "Package Integrity Evaluation-Sterile Products", states in section 3.4.1: "tracer gas tests performed using … laser-based gas headspace analysis [have] been shown to be sensitive enough to quantitatively analyze leakage through the smallest leak paths found to pose the smallest chance of liquid leakage or microbial ingress in rigid packaging." In addition, USP <1207> also states that "for such methods, the limit of detection can be mathematically predicted on the basis of gas flow kinetics." Using the above statements as a foundation, this paper presents a theoretical basis for predicting the gas ingress through well-defined defects in product vials sealed under a variety of headspace conditions. These calculated predictions were experimentally validated by comparing them to measurements of changes in the headspace oxygen content or total pressure for several different positive controls using laser-based headspace analysis. The results demonstrated that laser-based headspace analysis can, by readily differentiating between negative controls and positive controls with a range of defect sizes on the micron scale, be used to assess container closure integrity. The work also demontrated that caution must be used when attempting to correlate a leak rate to an idealized defect-size parameter.

Comparison of minimal leak test and manual cuff pressure measurement technique method for inflating the endotracheal tube cuff

Background: Appropriate management of endotracheal tube (ETT) cuff pressure is essential during mechanical ventilation of an intubated patient. The ETT cuff should be inflated in order to seal the airway without volume loss or pharyngeal content aspiration. It is desirable that the cuff seal the airway without exerting high pressure on the trachea to compromise mucosal circulation. The aim of this study is to assess importance of monitoring of ETT cuff pressure in intubated patients and effect of intervention in preventing complications related to over and under inflation of ETT cuff . Method: An observational prospective study performed between January and April 2015. All patients having cardiac surgery with cuffed ETT insertion were included. In Group1 cuff pressure manometer was used to monitor the cuff pressure and adjusted in the range of 20-30 cm H2O within 15 min before going on cardiopulmonary bypass. In Group2 only minimal leak test (MLT) done to guide inflation and cuff pressure measured by cuff pressure manometer but no intervention was made. Patients were followed in postsurgical care till extubation and observed till discharge for complication like sore throat, voice changes and tracheomalacia. Results: In group 1 9(25.7%) patient had cuff pressure within normal limit whereas 25 (71.4%) patient had cuff pressure higher than normal and 1 (2.9%) patient had cuff pressure measurement less than 20 cm H2O. Volume of air added or removed from cuff was -0.89 ± 1.14 to optimize cuff pressure. Cuff pressure ranged from 15 to 120(47 ± 23) cm H2O.In group 2 11(32.4%) patient had cuff pressure within normal limit whereas 22 (64.7%) patients had cuff pressure higher than normal and 1 (2.9%) patient had cuff pressure measurement less than 20 cm H2O. Cuff pressure ranged from 18 to 100(47.4±20.3) cm H2O. In group 1, 11 patients developed hoarse voice compared to 32 patients in group 2. P=0.000 In group 1, 15 patient developed sore throat versus 21 patients in gro