On line and global structural health monitoring of high temperature steam lines

高温蒸汽管道的在线和全局结构健康监测

• 批准号: EP/L504695/1
• 负责人: Tat-Hean Gan
• 金额: $ 21.6万
• 依托单位: Brunel University London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FL504695%2F1
• 关键词: line; global; structural; health; monitoring

Presently ultrasonic inspection of steam line welds involve taking off the pipe lagging and erecting scaffolding at outages.The time and expense involved in these processes mean that only 20% of the welds are inspected at any one outage and ittakes 10 years to achieve complete 100% inspection. So it is likely that some defects remain undiscovered until they are solarge (in excess of 50% of pipe CSA is not uncommon) and the failure probability correspondingly large that the need formajor and expensive repair becomes immediate and essential.The most obvious approach to 100% weld inspection, at first sight is to place close to the weld a ring array of conventionalMHz frequency compressional and angle beam probes i.e. the type of probes used in existing inspection methods appliedat outage. However, for coverage of the entire weld thickness the angle beam probes must the mechanically scannedthrough one skip distance normal to the weld line. Also fluid coupling is required with a limited lifetime at high temperatures.Alternatively permanent high temperature adhesives, of uncertain lifetime can be used but mechanical movement is thenprohibited.A far better solution is to use a single circumferential array located centrally on a pipe section between two welds phased topropagate a guide wave mode. By the use of longer wavelengths the number of transducers in the array, evenly spaced,can be lowered to 8 or even as little as 4 whilst still being able to insonify the entire pipe welds fairly evenly with a preferredwave mode, so to provide an array at far less cost than the previous options (1) and (2). At 250MHz, which implieswavelengths ~15mm, the propagation range is reach the welds at each pipe end, typically up to 6m. Reduction of thefrequency, for example down to 25kHz, wavelength ~ 150 mm, would increase the range to cover several pipe lengths,proportionality reducing the equipment costs of 100% inspection, at the expense of reduced inspection sensitivity(increased minimum detectable defect size). Accurate prediction of defect reflection coefficients and hence minimumdetectable defect sizes is only possible with a wave modeling technique such as finite element analysis but it quicker anduseful to obtain order of magnitude estimates using rules of thumb based on lower and upper sensitivity limits. Both theabove theoretical estimates apply strictly only close to the array because they take no account of the depth of the defectfrom the array or mode conversion losses along that depth. However as the waves are guided the wave intensity does notfall off as depth-2 or depth-1 as would 3 or 2 dimensional extensional waves, which indeed is why guided waves are oflonger range, for any given frequency and wavelength. Also mode conversion losses can be minimized by arranging for thetransmitted waves to contain as high a proportion as practically possible of a single non dispersive mode. This depends onthe array design. At the practical operating frequencies used for guide waves in pipes the wave absorption in the pipematerial is low, even at the maximum intended operating temperatures and will thus contribute little towards reducingdefect detection sensitivity. So in conclusion of these considerations the estimated can be credibly applied to the intendedarray-weld separation of ~6m. A further factor affecting the practical achievement of the highest feasible sensitivities is thedistribution of wave intensity along a radius from the inner to the outer wall. A distribution with strong maxima at the innerand outer surfaces is advantageous for simultaneous detection of inner and outer wall creep and fatigue cracksparticular.This illustrate the importance of modeling in the project to determine an optimum short list of modes which mightbe use sequentially to achieve the best 100% wall volume coverage.

目前，蒸汽管线焊缝的超声波检查包括拆除管道滞后和在中断时架设脚手架。这些过程所涉及的时间和费用意味着在任何一次停机中只有20%的焊缝被检查，并且需要10年才能完成100%的检查。因此，很可能有些缺陷直到它们很大时才被发现（超过管道CSA的50%并不罕见），并且相应的故障概率也很大，因此需要立即进行昂贵的重大维修。乍一看，最明显的100%焊缝检查方法是在焊缝附近放置一个传统mhz频率压缩和角束探头的环形阵列，即在现有的检查方法中使用的探头类型。然而，为了覆盖整个焊缝厚度，角束探头必须通过垂直于焊缝的一个跳距进行机械扫描。此外，流体耦合需要在高温下具有有限的使用寿命。也可以使用不确定寿命的永久性高温胶粘剂，但禁止机械运动。一个更好的解决方案是使用位于两个焊缝之间的管道部分中央的单个圆周阵列来传播导波模式。通过使用更长的波长，阵列中的换能器数量可以减少到8个，甚至只有4个，同时仍然能够用首选波模式相当均匀地对整个管道焊缝进行失谐，因此提供一个阵列，其成本远低于之前的选项(1)和(2)。在250MHz时，波长约为15mm，传播范围达到每个管道末端的焊缝，通常可达6m。降低频率，例如降低到25kHz，波长~ 150mm，将增加范围，以覆盖几个管道长度，按比例降低100%检测的设备成本，以降低检测灵敏度为代价（增加最小可检测缺陷尺寸）。缺陷反射系数的准确预测和最小可检测缺陷尺寸只能通过诸如有限元分析之类的波建模技术来实现，但使用基于上下灵敏度限制的经验法则来获得数量级估计更快更有用。上述两种理论估计严格地只适用于接近阵列，因为它们没有考虑阵列缺陷的深度或沿该深度的模式转换损失。然而，当波被引导时，波的强度不会像深度2或深度1那样下降，就像三维或二维的延伸波一样，这确实就是为什么对于任何给定的频率和波长，导波的范围都更长。此外，模式转换损失可以通过安排透射波包含尽可能高的比例，实际上可能的一个单一的非色散模式来最小化。这取决于阵列设计。在管道中用于导波的实际工作频率下，即使在预期的最高工作温度下，管道材料中的波吸收也很低，因此对降低缺陷检测灵敏度贡献不大。综上所述，计算结果可可靠地应用于~6m的焊缝间距。影响实际实现最高可行灵敏度的另一个因素是从内壁到外壁沿半径的波强度分布。内外表面有强最大值的分布有利于同时检测内外壁蠕变和疲劳裂纹。这说明了建模在项目中确定最佳模式列表的重要性，这些模式可以依次使用以实现最佳的100%墙壁体积覆盖率。

项目成果

High temperature performance of ultrasonic guided wave system for structural health monitoring of pipeline

• 发表时间: 2019
• 作者: A. Dhutti;T. Gan;W. Balachandran;J. Kanfoud

Advances in Structural Health Monitoring

结构健康监测的进展

• DOI: 10.5772/intechopen.83366
• 发表时间: 2019
• 作者: Dhutti A

Comparative study on the performance of high temperature piezoelectric materials for structural health monitoring using ultrasonic guided waves

• 发表时间: 2019
• 期刊: Science of Advanced Materials
• 影响因子: 0.9
• 作者: A. Dhutti;S. Tumin;T. Gan;J. Kanfoud;W. Balachandran

Development of Ultrasonic Guided Wave Transducer for Monitoring of High Temperature Pipelines

• DOI: 10.3390/s19245443
• 发表时间: 2019-12-02
• 期刊: SENSORS
• 影响因子: 3.9
• 作者: Dhutti, Anurag;Tumin, Saiful Asmin;Gan, Tat-Hean
• 通讯作者: Gan, Tat-Hean

High Temperature Gallium Orthophosphate Transducers for NDT

用于无损检测的高温正磷酸镓传感器

• DOI: 10.1016/j.proeng.2016.11.322
• 发表时间: 2016
• 期刊: Procedia Engineering
• 作者: Kostan M