Current state of safety testing of main pipelines

The paper briefly describes the history of quality testing of buried main pipelines. The pioneering research into the development of magnetic techniques for detection of flaws caused by corrosion in pipelines has been conducted at the Institute of Metal Physics of the Ural Division of Russian Academy of Sciences. The fairly high accuracy of measured parameters of detected flaws is confirmed. The topical problems concerning pipeline testing are formulated. Deceased.     

海底石油管道超声检测双向伞式变径技术

我国三种海底石油管道内径分别为Φ195mm、Φ247mm、Φ297mm,超声检测是管道壁厚变薄等缺陷的主要检测方法.为使超声检测装置能够适应三种管道的检测以节省成本,详细分析了适用于三种石油管道的超声探头排布方案;提出并论述了采用双向伞式机构实现超声探头保持架变径的原理,最后介绍了双向伞式变径装置结构设计的关键部分-铰链的结构设计.     

Monitoring stressed state of pipelines by magnetic parameters of metal

A method is described for assessing the residual life of pipelines and articles made of structural steels. Dependences between applied stresses and parameters of registered magnetic noises are shown. Criteria are suggested for assessing the in-service destruction of pipeline metal by its magnetic parameters.     

水载压力对管道超声导波信号的影响研究

为了研究水载压力对管道超声导波信号的影响,利用半解析有限元的方法分析了管道导波的频散曲线和波结构,选择 L(0,2)模态导波用于实验验证。 设计了一个可承受 30 MPa 压力的防水卡箍,对管道上的压电传感器进行封装。 将安装了防 水耐压卡箍的管道放入压力舱中进行打压循环测试,压力在 0~ 30 MPa 之间变化。 打压过程中采集无损伤及 5% 损伤的管道超 声导波信号,分析水载压力对导波信号的影响。 实验结果表明,该防水卡箍具有良好的防水和耐压性能,水载压力对 L(0,2)模 态导波信号幅值没有显著影响。     

False echo signals during ultrasonic testing of a steam generator

One important special case, namely, the ultrasonic testing of the welded joint of a steam generator was considered. The signal from a flaw is distinguished against a background of signals from technical reflectors.     

Ultrasonic testing of the stressed state of pipelines with consideration of the temperature factor

The effect of temperature changes on the estimation of biaxial stresses in pipelines by the acoustic method is considered. A method of using the acoustoelastic effect for the estimation of the uniaxial and biaxial stressed states using the changes in the propagation times of longitudinal and shear elastic waves along the normal to the surface of a pipe before and after changes in stress is described. Uniaxial stresses or the difference between biaxial stresses may be estimated by measuring mutually perpendicularly polarized shear wave delays, whose relative difference proportional to the stress value is temperature-independent. The algorithms for estimating the biaxial stresses incorporate parameters that are sensitive to the difference between the temperature dependences of the velocities of longitudinal and shear waves. Some experimental data on the estimation of the error of the method that were obtained at variable temperatures and the results of taking the temperature factor into account in the algorithms for estimating the stresses by the ultrasonic method are given.     

On the possibility of evaluating the stressed state of pipelines using a magnetic method

It is shown that the monitoring of the stressed state of pipelines with the use of a method based on the evaluation of magnetic properties of a pipe metal allows one to solve completely the problems of improving the reliability of a pipeline system of compressor shops, namely, evaluate the stressed state of pipelines, to detect stress concentration zones, monitor the change of stresses in a construction just during the repair of a pipeline and adjustment of pipeline supports, and optimize the character of the reduction in the stress level.     

The role of a stressed state in the formation of stress-corrosion flaws in pipelines

In recent years, as a result of performance of intensive in-tube flaw detection, the integrity and reliable operation of trunk pipelines have been achieved. However, because of an unpredictable development of such tube flaws as stress corrosion, the probability of occurrence of emergencies in pipelines substantially increases. An analysis of the stressed state in pipelines exposed to their main load—the operating pressure—and various types of additional forces is presented. As a result, it is shown that the obtained direction, value, and location of the effective maximum stresses in the tube wall fully correspond to the pattern of statistical formation of stress-corrosion flaws in pipelines. It can be concluded from the data of this study that the standardized tube-strength margin is insufficient; during tube operation, this circumstance may lead to the formation of stresses at the level of the metal yield stress and initiation and growth of stress-corrosion cracks.     

An acoustic method for diagnostics of the state of underground pipelines: New possibilities

The problem of the prevention of emergency situations on pipelines that are caused by leaks of a transferred product, unauthorized insertions, and installation of subversive munitions is considered. The approach to the detection of these threats with the use of an active method for acoustic diagnostics of the state of an underground pipeline is proposed.     

Diagnostics of corrosive state of main gas pipelines with module probe technology

A new method of measuring the corrosion rate of pipelines based on integration of the principle of polarization resistance into the module probe technology is developed for diagnostics of the corrosive state of pipelines. The experimental setup and the method for measuring the corrosion rate of metal objects in soil are developed. The efficiency of the setup and the possibility of recording the corrosion rate under the condition of long preliminary polarization are demonstrated. The results are of interest for development of new variants of diagnostics of the corrosive state of underground metal objects, technical diagnostics, and studies of physicomechanical characteristics of materials.     

超声车削弯曲振动系统的试验研究

设计并制造了三振型弯曲刀杆,计算出其固有频率为20．440kHz。空载下,用自行研制的超声车削弯曲振动装置进行了试验研究。得出刀具在切削速度方向的振幅符合其位移Catx=asinwt,呈正弦曲线,刀尖的振幅最大可达到18．1751μm,最小为10．3996μm,均能满足超声振动车削要求。     

Non-destructive ultrasonic velocimetry for central region velocity fields in turbulent Rayleigh-Bénard convection of mercury

A non-destructive method of measuring flow field of opaque fluids is presented for turbulent convection of liquid metal mercury. Two important properties of the turbulent state, namely 2D velocity profiles and energy spectrum, are successfully measured for Rayleigh-Bénard convection of mercury by using ultrasonic Doppler velocimetry. A few key techniques for the method are also explained.     

Estimating the technical state and safe operational life of pipelines from the results of in-tube nondestructive testing

The testing technique for examining the state and safe operational life of pipelines containing corrosion and stress-corrosion flaws is considered. This technique is currently used to examine the state of pipelines of OAO Gazprom. This technique is based on the processing and analysis of the database on the in-tube inspection of gas pipelines. The results of analysis provide estimation of safe operational lifetimes.     

Experimental investigation of the strain state in the ring-forging process

A method for calculating the strain state during three-dimensional plastic deformation is presented. The method is based on the measurement of the co-ordinates of net nodes marked on the surface to be investigated: in the present case the method is applied to the ring-forging process.Specimens were forged between the mandrel and a flat die and also between the mandrel and a die of inverted V-shape with included angle ϕ=135°. The results obtained in the tests allow an assessment of the influence of the relative width of the specimen, α (α=original width of the ring divided by its origianal outer diameter), and the relative diameter of the mandrel, δ (δ=diameter of the mandrel divided by the I.D. of the ring), on the strain state in the deformation zone.A flat die and a relative diameter of the mandrel of δ⩾0.8 afford less inhomogenity of strain and less irregularity of the cross-section in comparison with the results of using the inverted V-shaped die.     

空调冷凝器管道激光超声导波跨能量层级映射迁移检测方法

空调冷凝器是空调设备的关键部件,其弯管连接部位由于损伤类型多和几何形状复杂等原因造成传统接触式损伤检测手段难以应用,本文提出一种基于能量映射迁移网络的非接触式激光超声导波无损检测方法。首先,通过小波分解提取烧蚀信号和热弹信号的概貌波形,设计自编码能量映射函数将热弹信号特征空间映射到烧蚀信号特征空间,获得更接近烧蚀信号特征的映射热弹信号。其次,通过能量映射迁移网络对齐映射热弹信号和烧蚀信号特征空间,将网络模型中的域转换误差和样本标签误差之和用作特征空间对齐误差值。最后,对空调冷凝器泄漏、分层和裂纹等损伤进行检测实验验证所提新方法性能,结果表明其损伤识别精度为93.09%,比传统激光热弹激励检测方法提高了7.23%。     

高温再热蒸汽管道水压堵阀阀体裂纹的补焊

分析了高温再热管道水压堵阀阀体表面裂纹原因,制定了裂纹消除和焊接工艺措施。根据缺陷深度,采用镍基材料低温冷补焊和同质热补焊的两种补焊工艺方法,收到良好效果。     

Measurement of steam flow rates using a clamp-on ultrasonic flowmeter with various wetness fractions

Most of the heat in industrial plants is supplied by steam. To minimize energy waste, measuring the steam flow rates in existing pipes is important. Clamp-on ultrasonic flowmeters are used for this purpose, for which the sensors are attached to the pipe wall. However, flow conditions that can be used are limited because the signal-to-noise ratio of the ultrasonic signal in a steam flow is low. Furthermore, the steam wetness increases with heat losses, which may affect measurement results. Therefore, flow rate measurements in wet steam flows using clamp-on ultrasonic flowmeters have not been fully established. In this study, steam flow rates with various wetness fractions and system pressures were measured using a laboratory-made clamp-on ultrasonic flowmeter. The results show that flow rates in wet steam could be determined within a 10% error under general conditions in a steam piping system, although the conversion factor from line-average to area-average velocities was calibrated in superheated conditions, and the speed of sound in saturated conditions at each pressure was used. However, the error of the flow rates tended to increase with the wetness fraction and was biased toward positive values. The speed of sound and liquid volume fraction were evaluated at different wetness fractions. The flow rate error due to the change in sound speed was less than 1%, and 1.2% of the flow rates were overestimated owing to the liquid volume fraction. The velocity distribution in wet steam was considered different from that in the superheated steam owing to the existence of the liquid phase, and the change in velocity profile may lead to an overestimation of the steam flow rates in the wet steam condition.     

Effect of operation on the stressed state of process pipelines in a pressure blower’s piping

The possibility of assessing parameters of a stressed state from changes in magnetic properties is considered. Such an option would allow determining the sign and magnitude of the effective stresses. Generalized indicators of the stress state of a pipe’s cross section may include data on maximum, minimum, and average “pointlike” stress in the investigated cross section, the amplitudes of extreme values, and the average stresses in the segments of the investigated cross section. It is shown that application of such generalized characteristics of a pipeline’s stress state allows one to sequentially change the scale (selection) of the evaluated segment and compare technological-equipment units through the use of the advantages of the local testing of stresses in combination with averaged parameters of a pipeline’s segment that has a respective scale.     

Modal disturbance investigation of rod-shaped ultrasonic motor using bending vibrations

Modal disturbance of a rod-shaped ultrasonic motor using bending vibrations can cause problems such as low motor efficiency, instability, and poor control. In this paper, a dynamic analysis model of a stator is created on the basis of the finite element method (FEM) and Hamilton principle. The modal frequency sensitivities of the stator to the structure parameters are investigated by modal analysis. Accordingly, the structure parameters of the stator are modified to separate working modes from disturbance modes. A rod-shaped ultrasonic motor stator is fabricated, and the experimental results of its amplitude frequency response characteristics show that the purpose of modal separation is achieved. The frequency separation between working modes and disturbance modes is more than 2 kHz. The validity of the method is verified. __________ Translated from Piezoelectrics & Acoustooptics, 2008, 30(6) [译自: 压电与声光]