Leak detection in steam pipework

A large number of power stations worldwide contain steam pipework where welded joints can be susceptible to circumferential cracking close to or in the heat affected zone between the weld metal and the parent material. On occasions, cracks have grown significantly around the circumference of the welds and have penetrated through the pipework wall to produce small leaks. Although these leaks were detected before significant damage could occur, there is concern that violent failures could occur from undetected cracks.
At present the problem is contained by conducting rigorous but selective NDT at each shutdown on a representative sample of the critical welds. However, numbers of steam leaks have been successfully reduced, but it has not proved possible to eliminate them completely. Consequently, there remains a need to detect, and respond to those leaks which do occur as quickly as possible.
A programme of work was commissioned to investigate leak detection systems with the aim of devising a suitable system for power station use.     

Leak detection and measurements by vacuum bubblers

A simple vacuum bubbler device for visualising gas flows is described. The parameters controlling its sensitivity are examined from a physical viewpoint, and expressed in algebraic form for experimental testing. Experiments show that this theory of bubbling is adequate. The sensitivity can be varied over a wide range.     

真空设备检漏及探伤

随着技术的不断发展和更新,真空设备的种类和结构也越来越多样化,为确保生产的安全和高效性,结合设备的不同结构,对设备的检漏和探伤也提出不同的要求.分析传统的和最新的检测技术和手段,根据实际使用提出各自的使用范围和使用要点,以便生产和使用单位可以方便快捷的选择合适的检测手段和仪器.     

真空自耗电弧炉真空系统的检漏

主要论述了用于生产钛及钛合金铸锭的真空自耗电弧炉真空系统的组成与特点,针对钛、钛合金的冶金特点及生产实际,阐述真空系统漏率对于生产钛、钛合金的意义;应用最新技术的莱宝300型检漏仪,对真空系统进行了测漏,总结了检漏方法,此法对真空白耗电弧炉真空系统或类似的真空设备测点的设计、检漏具有指导意义.     

基于二氧化碳传感器的气密性检测方法

针对当前工业上泄漏检测方法存在检测精度低、成本高等缺点,设计一种微量泄漏检测方法。该方法利用二氧化碳气体作为示踪物质,充满纯二氧化碳气体的被测件通过标准漏孔产生泄漏,气体进入检测容器中,通过二氧化碳气敏传感器测量检测容器内二氧化碳浓度的变化得到微量气体泄漏的泄漏率。与工业生产中传统的气密性检测方法相比,该方法在提高准确度的同时保证测试的准确性,并且能降低成本。试验结果表明:该检测方法测试的准确性不受温度和湿度变化的影响;在不同压力测试条件下,实测值与标准漏孔参考值误差3%,验证方法的准确性;在相同压力测试条件下,测试结果相对标准偏差5%,实验重复性良好。     

Leak detection for transport pipelines based on autoregressivemodeling

A leak detection method based on autoregressive modeling is proposed. It requires only four pressure measurements, two at each end of the pipeline. A leak above 0.5% can be reliably and quickly detected by analyzing the time sequences of the pressure gradient at the inlet and outlet of the pipeline. It can be easily implemented because the computational expenditure is small. Its effectiveness has been verified by tests on a 10-mm-diameter, 120-m-long experimental water pipeline     

基于Duffing振子的天然气管道泄漏检测方法

针对天然气管道泄漏因泄漏声波信号信噪比(SNR)过低而难于检测的问题,研究了基于Duffing振子的天然气管道泄漏检测方法。该方法将待检测数据输入Duffing振子系统,以振子系统的状态转化实现非周期信号中周期信号的检测。为了更好地提高Duffing振子的检测性能,在Duffing振子设计阶段,以随机共振的有关理论为基础,通过对系统输出信噪比的优化来实现Duffing振子的参数设计。基于实际天然气管道泄漏数据的测试结果表明,所提出方法可在低信噪比(-68dB)的情况下有效检测出泄漏,具有较好的检测性能。     

氦质谱检漏仪的误差分析

本文通过对氦质谱检漏仪产生误差的各种因素进行综合分析,运用误差理论,最后计算出合成误差．     

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.     

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.     

Microfluidic device for airborne BTEX detection

We fabricated a microfluidic device for the optical detection of airborne benzene, toluene, ethylbenzene and xylenes (BTEX). The device consists of concentration and detection cells formed of 3 cm x 1 cm Pyrex plates. The concentration cell is composed of an adsorbent to concentrate the BTEX gases and a thin-film heater todesorb the concentrated gases from the adsorbent thermally. The collected gases are introduced into the detection cell, which is connected to optical fibers, to measure their absorption spectra. We optimized the device's operating conditions by studying the thermal characteristics of the concentration cell and the time profile of the gas concentration flowing in the detection cell. We used the device under optimized operating conditions to detect toluene gas as a typical example BTEX. The gas concentration amplification rate was approximately 2 orders of magnitude, and we successfully measured parts-per-million levels of toluene gas with this device.     

A device for gated autosynchronous luminescence detection

The sensitive detection of delayed luminescence (τ > 100 μs) can be achieved with an optomechanical instrument, the gated autosynchronous luminescence detector (GALD). The device effectively combines an excitation chopper, a detection chopper, and a dichroic mirror into a single element. With dimensions of 12 mm (H), 32 mm (W), and 90 mm (L), it is designed for insertion into the differential interference contrast (DIC) prism slot of a BX51 Olympus microscope. The GALD described here employed a compact high-power UV LED as the excitation source to capture images of Giardia lamblia cysts indirectly labeled with a europium chelate/streptavidin conjugate. Labeled cells were clearly visible in the complete absence of autofluorescence and signal intensity was sufficient to capture high-resolution color images within several seconds. Shorter exposure intervals of 100 ms on a monochrome Andor iXON camera delivered time-gated luminescence images with a signal-to-noise ratio better than 114:1.     

85 m3液氢铁路槽车的检漏和抽空

介绍了85 m3液氢铁路槽车首次定期检修过程中检漏与抽真空的设备配置、系统组成和实施工艺,对槽车夹层气体进行了质谱分析,对检漏工艺和抽空工艺的实施经验进行了分析.结果表明:氢气、水气和氮气是夹层的主要气体成分,首先进行检漏可为后面抽空提供前提条件,热氮冲洗置换和间断抽空排气的抽空工艺可以大大缩短抽空时间,得出了抽空时间与漏放气速率变化的规律.     

Phage display antibody-based proteomic device using resonance-enhanced detection

The combination of phage display antibody arrays with a novel nanotransducer technique based on resonant nanoparticles in a nanosandwiched film enables the sensitive parallel screening of proteins. Using the resonance of nanoparticles with their induced mirror dipoles in a thin-film structure, limitations of fluorophores, such as unspecific background and nonvisibility to the eye, can be overcome, thereby leading to an optical signal significantly more sensitive than that of standard colloid techniques. The signal can be both directly observed as a color change of a microdot at the sensor surface and tuned throughout the visible range of the spectrum. Here we report the application of an optical chip using scFv-antibody-antigen interactions. Artificial scFv-antibodies against a variety of proteins, including yeast enzymes and bovine serum albumin (as a standard), were constructed via Phage Display. These scFv-antibodies were then coated onto metal nanoclusters and bound to their antigens that were arrayed as nanodroplets at the resonance layer of the chip. ScFv-Antibody-antigen interaction resulted in a visible array of microdots. Using resonance-enhanced absorption, the absorption signal of the spots was amplified by one to two orders of magnitude (compared to colloid-based techniques). For quantitative analysis, either an 8-micron scanner or a CCD camera (resolution 4 microns) was employed to gain direct-reflection spectra rather than unspecific scatter data (prone to dust and unspecific interaction). Our results demonstrate that this device enables high-throughput proteomics to overcome some limitations of fluorescence, enzyme labels, and colloid techniques.     

基于标准漏孔比对法的漏率测量装置

针对真空密封件的密封性能评估,采用了基于标准漏孔比对的漏率测量方法,具体包括动态比对法和静态累积比对法,通过四极质谱仪比较标准漏孔和密封件流出气体产生的离子流,利用标准漏孔的已知漏率和四极质谱离子响应的线性外推,计算密封件的漏率。研制了一套密封件的漏率测量装置,装置极限真空可达10^-7Pa量级,漏率测量范围为:10^-7-10^-14Pa·m³/s,可用于具有检漏接口的各类密封件的漏率测试。采用该装置的两种方法分别进行不锈钢刀口密封件的漏率测试。结果表明:动态比对法对该不锈钢刀口密封件的漏率测试误差较大,低于10^-11Pa·m³/s量级的极低漏率密封件更适合采用静态累积比对法进行测试。     

管道泄漏数学模型及测试技术

通过分析建立管道泄漏数学模型,研究泄漏引发的瞬态负压波在管道中的传播过程,编制离线软件模拟管道泄漏事故.在此基础上,运用瞬态负压波法在实验环道上进行泄漏监测实验.实验数据采集系统由HB26S型扩散硅压力传感器和PCI-1800L型A/D采集转换芯片组成,采集设在环道首末端处监测点的压力信号,并以此信号判断泄漏是否发生.运用信号相关处理方法对环道首末端监测点的压力信号进行处理,得到泄漏引发的瞬态负压波传播到环道首末端监测点的时间差,实现漏点的定位.实验结果验证了瞬态负压波泄漏检测方法的有效性和极性相关漏点定位法准确性.     

Amorphous ferroelectric thin film capacitive device for hydrogen detection

Hydrogen is a promising alternative energy source for next generation automobile engines that meet the concern of energy shortage and global environmental pollution. Hydrogen detection is an important associated technology to be developed. The recently developed amorphous ferroelectric thin film capacitive gas sensors with a largely improved sensitivity to hydrogen show a great potential for this associated technology. This review presents an overall picture of amorphous ferroelectric thin film hydrogen gas sensors. It focuses on the correlation among processing, microstructural evolution and electrical properties of amorphous ferroelectric thin films. An attempt is made to detail the hydrogen sensitivity and transient response of various prototype capacitive devices with respect to the quality of the films and the hydrogen kinetic processes in the Pd/ferroelectric heterostructure. Recent advances on the hydrogen interface-blocking model for amorphous ferroelectric gas sensors are also described.