基于分子流传感元件的真空腔体漏率测量方法

本文介绍了一种基于分子流传感元件的真空腔体漏率测量方法,该方法通过分子流传感元件测量真空腔体整体漏率,采用的测量装置由气体流量测量系统、真空抽气系统、恒温系统等部分组成.在测量系统中,流经传感元件的气流处于分子流状态,通过测量传感元件两端的差压,计算质量流量,可以得到真空腔体的整体漏率.实验中对多个真空腔体漏率的测量结...     

大型低温容器氦质谱定量检漏方法

漏率指标是评价大型低温容器产品质量的主要技术指标之一,准确定量漏率值是产品绝热性、可靠性和安全性的重要保证.本文详述了大型低温容器检漏系统的配置、检漏系统最小可检漏率的估算、反应时间确定,并给出了氦质谱定量检漏方法.     

正压漏孔校准装置优化设计

针对目前正压漏孔校准工作中存在的测量下限指标低、测量不确定度大等问题,提出了正压漏孔校准装置的优化设计方法.采用特殊设计,将定容室的容积减小到10 mL以下,降低了气体累计时间,延伸了测量下限.采用主、被动相结合的恒温方法提高恒温精度,使得测量系统温度变化在校准时间内小于0.02 K,减小了温度漂移引入的虚流量及测量不确定度.在恒压法正压漏孔校准方法中,提出采用直径小于1 mm的精密细活塞及适用的动密封结构.可以将测量下限延伸到10-7Pa·m3/s 量级.通过以上方法,可使正压漏孔校准装置的测量下限优于5×10-7 Pa·m3/s,不确定度小于5%,同时具有较高的工作效率.     

碳管炉真空系统的检漏

本文主要论述了碳管炉真空系统的组成及特点,利用静态压升检漏法和氦质谱检漏两种手段评定碳管炉密封性的好坏,此方法对真空热处理设备及类似装备的设计、检漏具有很好的指导意义.     

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.     

Mass Point Leak Rate Technique with Uncertainty Analysis

The mass point leak rate technique is often the methodology of choice for quantifying leak rates as it uses simple elementary measurements, applies to gas systems of low mass, proves effective for low leak rates, and does not rely on test-gas conversions. In this methodology, a number of instantaneous mass measurements are calculated through samples of volume, pressure, gas composition, and temperature measurements over time. A regression analysis of the corresponding mass-time sample set yields the leak rate of the system. A detailed uncertainty analysis is paramount for a complete, experimental characterization of the leak rate and previously was not fully implemented in the mass point leak rate method. Recent advancements in regression uncertainty analysis by propagation of errors afford the ability to quantify the uncertainty with estimates of covariance in the regression results. The mass point leak rate technique with the associated detailed measurement uncertainty analysis offers the ability to quantify both the leak rate and the uncertainty associated with the leak rate value. Detailed herein is the development of the methodology and a detailed uncertainty analysis that includes both precision (repeatability) and bias (systematic) error. Alternative leak rate methods are also discussed for comparison purposes. An example in the methodology is presented.     

Refrigerant leakage detection in an EEV installed residential air conditioner with limited sensor installations

Refrigerant leakage is the most frequently found fault in a refrigeration system and efficient detection is highly important. For a sudden leakage, it is relatively easy to detect but slow and long-term leakage is hard to find out, therefore, a useful method for leak detection in such condition is required. Large scale refrigeration systems have abundant data to detect or diagnose leakage. However, in case of small residential air conditioner, installed sensors are mostly temperature sensors, and the number of these sensors is also limited. In this study, a refrigerant leak detection method for an EEV (electronic expansion valve) installed residential air conditioners with limited sensor information is suggested based on experimental data. This method uses temperature differences between inlet air and midpoint of heat exchanger. For various temperature conditions, the temperature difference shows a similar trend which can be utilized as a good leak detection procedure.     

冷媒气体泄漏率的定量分析

工业上一般使用标准漏孔对冷媒检漏仪进行定性检测,由于它的便捷性而得到广泛使用。近年来,对标准漏孔的溯源方式和校准方法进行探索逐渐进入人们的视野,冷媒气体泄漏率的定量分析和测量过程的不确定度评估定量分析就显得尤为重要。通过建立数学模型,对标准漏孔在测量过程中影响测量不确定度的因素进行分析和量化。最后通过实验验证,测量结果的相对扩展不确定度约为4%,可以满足了泄漏率量值传递过程中10%的要求。     

Moderne Lecksucher mit Vakuumtechnik

Modern leak detectors in vacuum technology In many areas of industrial manufacturing, quantitative leak tightness measurements are required in order to analyze product quality. This article examines three approaches to vacuum leak testing, which utilize different measuring principles and completely different working pressures. The processes are divided into “non-gas selective”, “single gas selective” and “double gas selective”. The pressure rise method does not work gas-selectively. In so-called foil test chambers the pressure rise measurement is used in optimized design and is particularly suitable for leak testing in the food industry. The classic test gas vacuum leak detection is a gas-selective method. The test gas is selectively detected and the chamber is pumped independently of the type of gas. Major innovations in current device solutions are the extension of the measuring range and improved convenience in use. To achieve a detection limit of less than 10⁻¹² mbar·l/s, a double gas selective operation is used, residual gases from the test chamber are selectively pumped, additionally, the test gas detection is selective.     

大型真空系统氦检漏率的快速准确检测方法

大型真空系统检漏往往耗时长、效率低。本文分析了氦气通过漏孔进入氦质谱检漏仪形成检漏信号的规律,并据此建立检漏信号数学模型,确定漏孔的最终稳态泄漏信号。基于上述分析,提出漏孔漏率的一种快速预测方法。该方法用于大型真空系统检漏能准确预测被检部位的漏率,能显著缩短检漏时间,提高检漏效率。     

A probabilistic simulation of fluid leakage in multiple cracks situation

ABSTRACT In pressure vessels and piping the leak‐before‐break (LBB) assessment method is employed to avoid any catastrophic failure prior to a detectable leakage. One of the most important parameter, the leak rate, is investigated in the present paper by means of the Monte Carlo method. A brief review is carried out with emphasis on aspects such as crack growth, crack size with detectable leakage, crack opening area and leak rate. Issues concerning the property and behaviour of multiple cracks are also covered along with a review of the characteristics of leak rate through distributed multiple cracks using a statistical simulation method. The simulation results show that the effect of multiple cracks is quite significant to the LBB concept. Both the relationship between leak rate and crack length (or time) and the statistical characteristics of the leak rate are considerably different for different initial crack conditions.     

温度对正压漏孔校准装置本底漏率影响的研究

在实验室条件下,由于温度变化引起正压漏孔校准装置本底漏率变化是影响正压漏孔校准下限的主要因素,因此正压漏孔校准装置采用水浴恒温技术,采取主动恒温与被动恒温相结合的方式进行恒温,以减小因温度变化对本底漏率的影响。通过实验研究,采取恒温措施后,本底漏率降低到1.36×10-9Pa×m3/s,正压漏孔的测量下限可以扩展到2.667×10-8Pa×m3/s,延伸了正压漏孔标准的下限。     

Kalibrierung von Schnüffel‐Testlecks

Calibration of reference leaks for testing leak sniffers Functionality, safety and environment protection require the tightness of equipment against atmosphere. To check for possible leaks, commercial leak sniffers are commonly used. In order to warrant the reliability of leak testing, the sniffers must work properly with correct sensitivity at usage. To prove the proper operation of the leak sniffer, test leaks with known leak rates are used. The present paper deals with design and calibration of the test leaks, in particular for very small leakage.     

Local Measurement of Stress–Strain Behaviour of Ductile Materials at Elevated Temperatures in a Split‐Hopkinson Tension Bar System

A split‐Hopkinson tension bar system is modified to allow for measuring the stress–strain behaviour of ductile materials at large strains, high strain rates and elevated temperatures. The specimen is heated by induction, and a pyrometer provides a laser‐based temperature measurement that controls the testing temperature in a feed‐back loop. A high‐speed digital camera system and an edge detection algorithm are used to obtain local measures of strain after necking of the axisymmetric specimens. Using the local strain measurements and Bridgman's analytical formulas, it is feasible to find the equivalent stress–strain curve to fracture for different levels of strain rate and temperature. Thermal and thermo‐mechanical finite element simulations of the test set‐up are used to evaluate the validity of the proposed experimental method.     

Prüflecks für Schnüffel‐Lecksucher

In the testing of leak tightness and in the localisation of leaks by means of a test gas, proper operation and sensitivity of the employed instrument must be checked by a certified reference leak. In the so‐called sniffer mode of operation, the component under test is filled to overpressure with the test gas, so that in case of a leak there is a gas flow from the component to atmosphere. The atmospheric gas is sucked by the instrument and probed for its test gas content. For checking the instruments performance, commercial test leaks are available for various gas species, which deliver a well‐defined leakage. Construction and properties of such a test leak are described. The leak has an internal gas reservoir and a capillary as leak element. Because the inlet pressure at the capillary is kept constant by a pressure controller, the leakage remains constant over several years despite the gradual pressure decrease in the gas reservoir. The calibration of the leakage via the volume flow rate is described in detail. The volume flow rate can be measured by a liquid drop in a measuring capillary as well as a displacement piston in a dosing syringe.     

金属压扁型正压漏孔不同压力下的漏率研究

在不同入口和出口压力条件下,正压漏孔的漏率值会发生变化,在使用时需要对正压漏孔的校准值进行修正。对2支金属压扁型正压漏孔在多种压力条件下进行漏率测量,给出了测量结果,然后根据管道流导理论推导出正压漏孔漏率随压力变化的修正公式,并对修正结果与实验测量数据进行了研究分析。     

Hochempfindliche Dichtheitsprüfung mit Spürgas SF6 und Laser‐Gasnachweis

At the Institute of Technical Physics of the Research Center Karlsruhe, superconducting magnets for fusion reactors are tested in the test tank TOSKA since more than 20 years. A crucial test parameter of the magnets weighing up to 120 metric tons is the tightness at operating conditions down to 2 K temperature and max. 25 bars He‐refrigerant pressure. Because the final tests at cryo‐temperature are costly and time‐consuming, intermediate tests at room temperature are already performed at the stages of manufacturing, certification, assembling, and before cooling‐down. So far, these tightness tests by the sniffermethod have been performed with probe gas Helium employing a conventional mass spectrometer leak detector. The achievable smallest detectable leakage is limited by the He partial pressure in ambient air. Therefore, a new technique of leak measurement was investigated using the probe gas sulphur hexafluoride SF₆ which does not occur in natural air and employing a laser‐acoustical gas detection. The experimental results reveal substantial advantages of the new method with respect to detection sensitivity, testing expenditure, and costs. The results can be transferred to tightness tests in other fields of technology.     

Helium‐Testlecks

Helium test leaks Leak localization and tightness control with Helium provides a very sensitive testing method. Frequently, the sensitivity of a leak has to be testspecified quantitatively. In particular, quality control requires a reliable verification of the sensitivity. For this purpose, test leaks with well‐known leakage are used. In the article, various types of test leaks and their properties are described. Test leaks are commercially available over a wide range of leak rates. Their leakage flow can be calibrated with good accuracy. In the usage of the test leaks, the temperature‐dependency of the leak rate has to be taken into account, as well as the slow decrease of the leak rate due to the continuous loss of gas from the reservoir.     

Die Hauptstrommessung als Innovation in der industriellen Helium‐Dichtheitsprüfung

Main flow measurement as an innovation in industrial helium leak testing So‐called main flow measurement with its special vacuum pump stations brings numerous technological advantages to helium leak testing, making it possible to significantly enhance the cost profile and efficiency of industrial inline test systems. The suppression of ambient influences and the achievability of the shortest clock rates are the key factors for the successful automation of test processes. The reduction in helium consumption and the achievable energy savings improve the cost benefits of investing in a test system working on the main flow principle still further. PINK leak test systems are equipped with numerous diagnostic features ranging from continuous self‐monitoring and fully automatic leak rate control to the independent calculation of new test parameters.     

低温绝热容器氦质谱检漏方法探讨

漏率是低温绝热容器产品的主要技术参数之一,利用氦质谱检漏技术对漏孔进行定位、定量检测可以起到控制产品质量的目的。文章首先对低温绝热容器用两种氦质谱检漏系统进行了比较和试验分析。结果表明：在测试条件一致的情况下,标准漏孔安装在系统中的不同位置,将对系统最小可检漏率、系统反应时间、漏率测算值产生影响。在对影响结果进行分析的基础上,对实际检漏工作提出相应建议。其次对分流和无分流两种检漏方法的选择原则进行了探讨。然后以53m^3液化天然气储运容器为例,对容器制造过程中的角焊缝、对接焊缝、夹层内存在的漏孔、阀门及容器整体的检漏方法进行了详述。最后对检漏过程中应注意的事项进行了说明。