L(0,2)模态在管道内壁附着物测厚中的应用

Thickness Measurement of Inner Surface Attachment of Pipes with L( 0,2) Mode

管道内壁附着物厚度的状况,是工业生产安全性评价的一项重要指标.以有机热载体炉为例,其管道内壁的积碳层极易造成加热炉管的某些部位局部过热,导致爆管发生,造成人员伤亡.本文分析L(0,2)模态在双层管道中的传播特性后提出,利用110k Hz下L(0,2)模态导波的群速度随管道内壁附着物厚度增长单调减小的特性,无损定量地检测外径57mm,壁厚3.5mm管道的内壁均匀附着物的厚度.随后建立了管道内壁附着物厚度定量检测系统,利用中心频率为110k Hz的压电斜探头以非对称加载的方式对内壁附着有0、1、1.5、2和2.5mm均匀模拟积碳的管道试样进行了35组实验研究.实验结果表明,L(0,2)模态群速度的实验值与理论值的总体变化趋势保持了一致.利用本方法可以定量检测管道内壁附着物的厚度,对安放空间狭小、无法沿管道周向布置阵列传感器的工业管道的检测具有很好的实用意义,并且对于后续的探头开发具有指导意义.

The thickness of internal pipe attachments is an important factor in industrial safety evaluation. Using the organic heat transfer heater as an example,the deposited carbon layer on the inner surface of pipes often causes local overheating,leading to pipeline explosion and casualties. This paper analyzed a nondestructive technique for measuring pipe attachment thickness using the L( 0,2) vibrational mode in double layer pipes. Internal attachment thickness of pipes was determined by measuring decreased group velocity in thicker regions of pipe at frequencies of 110 k Hz. An experimental system with two angled beam probes( center frequency 110 k Hz) was established to measure 5 pipes( outer diameter 57 mm,pipe wall thickness 3. 5mm),with uniform inner surface attachments of 0,1,1. 5,2 and 2. 5mm. 35 groups of data are obtained. Results show that the changing trend of experimental values are consistent with theoretical values. This method can quantitatively measure the thickness of interior pipe attachments with potential to be utilized in narrow spaces not suitable for array sensors in industrial inspection,as well as guide future research on probes.