Die Dichtheitsprüfung an Beschichtungsanlagen

Leakage Detection in Coating Equipment — Details on Best Practice Based on long term experience the authors give practical advice to users/operators to find the optimum installation, positioning and operation of the Helium leak detector for leak detection on a coating/metallizing plant and its gas supply system. Physical effects and dependencies are explained influence the response and whichrecovery times. The use of auxiliary pumps for evacuation of larger volumes and the partial flow ratio resulting from this procedure are discussed. General advises complement the article.     

A sniffing attachment with improved response time and sensitivity

A sniffing attachment with improved sensitivity and response and clean up times for use with a helium leak detector has been developed. The attachment consists of a zeolite trap cooled to liquid nitrogen temperature in series with a sniffing leak which is much bigger than those normally used in the probes. Response time of the order of 12.5 s and detection limit of 50 ppb helium concentration are obtained without difficulty. It has been used over a period of nearly 1 year and has given satisfactory performance.     

真空混合漏孔示漏气体的延迟和保持特性研究

真空混合漏孔 ,如漏孔通道内含有空腔、毛细管道等 ,示漏气体除存在超长反应时间外 ,还存在超长的延迟时间和保持时间。只有经该延迟时间后 ,检漏仪才能探得信号。为满足真空元件在生产中的快速检漏的要求 ,又避免常规质谱检漏法漏检混合漏孔的可能性 ,在真空室内对检漏元件集体充氦 ,然后在保持期内逐个检测氦气浓度来判断有无混合漏孔 ;也可用质谱计比较残余气质谱图中空气成分来确定     

Industrielle Vakuumlecksuche mit intelligenten Gas‐Leckdetektoren: nicht nur ein Massenspektrometer. Industrial Vacuum Leak Detection with Intelligent Gas Leak Detectors: not only a Mass Spectrometer

In recent years, the requirements on reliability and lifetime of industrial components have increased significantly. This is due both to customer requirements and the Total Quality philosophy that has been introduced much more widespread. This development has had an impact especially on industrial leak detection since this is one of the non‐destructive testing techniques that has been at a rather low level both regarding the involved technologies and the training of personnel. Modern leak detectors that use test gases, especially helium, for testing components and systems have addressed these needs. In a most important first step, already 20 years ago, helium leak detectors got rid of liquid nitrogen traps by introducing counter flow technology. This together with the replacement of manual valves by electromagnetic ones controlled by a microprocessor enabled operation by relatively unskilled persons in industrial processes. In the following years efforts concentrated on lowering the detection limit and the helium signal response time of the new method. The introduction of dry pumping systems (required by the semiconductor industry) was an additional challenge to be mastered in parallel to those efforts. With the latest instruments, and that is the major concern of this article, operation under industrial conditions was optimized now also focusing on background signal handling which is mandatory for a quick pump‐down of large vessels (up to 100 liters of volume) and unambiguous detection of leaks under contamination conditions. Reaching the leak rate range below 1x10^–9mbarl/s within a few minutes when pumping a 100 liter vessel is one of the specifications to be achieved. Several 1000ppm of ambient helium background or contamination of elastomer gaskets must not produce long waiting times with no value added. It is not surprising that beside new pumping technologies software is more and more an important part of modern leak detectors. There are ways of dealing with signal instabilities to increase the detection limit for leak rates, it is possible to reduce the effect of water vapour desorption on the pump‐down time for large volume vessels without LN2, there are more and more sophisticated ways of “ZERO” functions and non‐linearity compensations for high total pressure operation. These developments are explained and demonstrated with some examples of modern leak detectors recently introduced into the market.     

无油真空检漏系统在空间环境模拟试验中的应用

介绍了我国某小型空间环境模拟无油检漏试验设备,并就无油真空系统、检漏系统灵敏度和反应时间等问题作了详细介绍,大量试验证明该无油检漏系统的设计是合理和正确的.     

Helium‐Testlecks zur Kalibrierung von Lecksuchern

In order to perform reliable quantitative measurements of leak rates, the used leak detection equipment is calibrated by injection of a known leakage flow delivered by a test leak. Well‐proven are Helium test leaks of the diffusion type with internal gas reservoir. The present paper deals with the construction of such leaks, the temperature dependence and response time of the leak rate, and their calibration. In case of careful handling, the relative uncertainty of the delivered leakage flow can amount to only 3 % (2σ).     

Reliability Enhancement in Nondestructive Evaluation: Development of Practical Rules for Vacuum Type Helium Leak Tests

In helium leak testing, reliability is an important factor and while attempting to improve this, lot of challenges are being faced. There are contributors for bringing in variations in leak meter readings obtained during system sensitivity check and actual leak test which ultimately affect the final measured leakage rate of test object and they need to be controlled for obtaining reliable results. Response times of leaks are affected by vacuum side volumes, contaminations in vacuum side, leaked gas travel path restrictions on vacuum side and nature of actual leak paths and their gas flow impedances. Hence, actual consideration of real responses of leaks is to be practiced for a reliable test. The traditional concept of using estimate for percentage helium concentration in test hoods is modified by a novel method for its exact determination which improves reliability in tests. Also, practical rules are derived for the reliable identification of leak locations from response time concept. Spurious indications caused by leaks in temporary test rig joints or due to leaks from joints or passages not in the scope of test are other impediments for a reliable test. The response of system changes instantly by spurious indications and hence they require elimination by adopting innovative methods.     

基于压电传感器的管道泄漏信号可靠性识别技术研究

管道泄漏检测的可靠性主要取决于泄漏信号的信噪比,泄漏信号信噪比的提高主要由传感器和对信号的处理方法决定。在定量分析的基础上,得出了基于压电传感器的管道泄漏检测方法具有比基于压力传感器的负压波法更高的泄漏信号信噪比。通过信号分析,论证了平滑滤波对于提高泄漏信号信噪比的必要性,提出了用区间信号能量来突出泄漏信号的方法。分析比较了实际检测信号幅值、区间信号能量和区间信号平均能量的平方3种方法下泄漏信号的信噪比,提出了用基于区间信号平均能量平方的顺序能量比率法进行管道泄漏信号识别的方法。结果表明该方法可以极大地提高泄漏信号信噪比和泄漏检测可靠性。     

Development of vacuum technology market in Russia. Entwicklung des Marktes für Vakuumtechnik in Russland

Scientific investigations of leak detection problems are being carried out in several directions. The most significant are metrology problems. Mathematical modeling of working processes in new types of leak detectors is also being developed. Mass spectrometer leak detectors remain the most popular for high accuracy measurements. Other types of leak detectors, such as halogen, manometer, and gas discharge, are also developing. Different types of gas discharge leak detectors are being manufactured.     

冰箱制冷系统检漏方法探讨

总结了冰箱制冷系统检漏经验,并参考了国外先进的检漏方法,提出在冰箱制造过程中,除制冷系统注入F_(12)后的管路焊口用卤素仪检漏外,系统的其他零部件和连接管路焊口都应当采用氮质谱仪检漏。本文介绍了冰箱制冷系统的几种检漏方法及其比较,还介绍了国外目前生产的以氦质谱仪为核心的几种检漏设备。     

推进剂泄漏检测比对技术研究

卫星推进剂泄漏检测是航天器发射任务中的一个重要环节,它可以保证人员和产品安全,防止安全事故的发生。但是检测仪器的校准一直是行业内的难题。介绍一种推进剂泄漏检测比对装置的结构原理、泄漏模拟源获得方式以及比对实验方法,给出了无水肼模拟源扩散率实验和比对因子测量结果。     

Dichtheitsprüfung

Leakage Tests — Flexible packaging in food processing and pharmaceutical industry Extended storage life for food products or better protection against environmental influences increases the demand for more accurate leak detection methods. Flexible, and therefore more fragile packaging is even more complicated when it comes to the commonly required non destructive leak testing. The main focus when testing flexible packaging is on welded seams. They represent the weakest point in flexible packaging. Today, there are several leak detection methods used to perform tests on flexible packaging. The most common ones are waterbath, pressure/vacuum decay and tracer gas based leak detection. All of which have their strength and weaknesses wheras the desired reject leak rate is mostly influencig the decision process. To measure very small leaks (<10 μ oder 10^‐5 mbar l/s) or to enable very short test cycles, trace gas leak detection is the way to go. On top of high accuracy, tracer gas leak detection also allows the precise localization of the leak. Nevertheless, the mechanical stress applied to the flexible packaging due to the vacuum required for tracer gast testing is not an easy task to cope with.     

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。     

Normen für Lecksuche und Dichtheitsprüfung

Standards for leak detection and leak testing This article summarizes national and international standards of relevance for leak detection and tightness control. Content of regulations of special interest for vacuum technology is presented. In addition, regulations are introduced which are of relevance for industrial tightness control.     

ZQJ-291检漏仪在真空检漏设备数据采集系统中的应用

通过对检漏仪的通讯原理的分析,介绍了 ZQJ-291检漏仪在真空检漏设备数据采集系统中的应用.针对提高真空检漏设备的自动化水平的目标,详细阐述了ZQJ-291检漏仪终端软件的开发思路及关键功能的实现,在文章的最后对软件界面进行了展示.     

大型超长贮箱立式泄漏检测技术研究

针对新一代运载火箭大型超长贮箱氦质谱泄漏检测的需要,本文提出了立式检漏的工艺方法。针对立式检漏中可能存在的由于高度差及重力因素产生的气体分层问题,本文从理论分析和模拟试验验证两个方面分别开展了深入研究。通过理论和试验的对比表明,大型超长贮箱立式检漏时不会产生明显的氦气分层,由分层造成的漏率测量误差可忽略不计,立式泄漏检测技术具备工程应用的可行性。     

氦质谱非真空积累检漏法中几个问题的研究

氦质谱非真空积累检漏法被广泛应用于航天器的总漏率测试中,因此研究氦质谱非真空检漏法具有重要的工程实际意义。本文首次详细给出了氦质谱非真空积累检漏法计算公式的详细推导过程,同时讨论了采用柔性收集室技术可能产生的一些问题。研究结果表明:氦质谱非真空积累检漏法有着严格的理论依据;柔性收集室的技术在理论上是可行的。本文的研究结论可以为氦质谱非真空积累检漏法的工程应用提供理论依据。     

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.     

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.     

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.