Abstract：
The ultrasonic pulse-echo technique is widely employed to measure the wall thickness reduction due to corrosion in pipelines. Ultrasonic monitoring is noninvasive and can be performed online to evaluate the structural health of pipelines. Although ultrasound is a robust technique, it presents two main difficulties arising from the temperature variation in the medium being monitored: the mechanical assembly must have high stability and the ultrasonic propagation velocity must take into account the temperature variation. In this paper, a detailed strategy is presented to compensate for changes in the propagation velocity whenever the temperature changes. The method is considered self-compensated because the calibration data is obtained from the ultrasonic signals captured using the pipe under evaluation. The analysis of systematic errors in the temperature compensation is presented, first considering that a reference initial pipe thickness is given, and second when a reference sound velocity is given. The technique was evaluated under laboratory conditions using a closed loop with accelerated corrosion through the use of continuous flow saline water containing sand. In this test, the ultrasonic results were compared with the traditional coupon method used to determine corrosion loss. The results show that the self-compensated method was able to compensate for temperature fluctuations, and the total thickness loss measured by the ultrasound technique was close to the value measured by the coupons. Finally, the measurement system was tested in a production pipeline exposed to sunlight. The results show that the self-compensated method can reduce the oscillations in the thickness loss readings, caused by temperature swings, but large temperature variations cannot be completely compensated for. This experiment also shows the effects of low mechanical stability, which caused completely invalid results.
摘要：
超声脉冲回波技术被广泛用于测量由于管道腐蚀而导致的壁厚减小。超声波监测是非侵入性的，可以在线进行，以评估管道的结构健康。虽然超声波是一种强大的技术，它提出了两个主要困难引起的温度变化在介质被监测:机械组件必须具有高稳定性和超声波传播速度必须考虑到温度变化。在本文中,提出了一种详细的策略来补偿温度变化时传播速度的变化。该方法被认为是自补偿的，因为校准数据是从使用评估中的管道捕获的超声信号中获得的。分析了温度补偿中的系统误差,首先考虑给出参考初始管道厚度，第二，当给出参考声速时。该技术是在实验室条件下通过使用含有沙子的连续流盐水加速腐蚀的闭环进行评估的。在这个测试中,将超声结果与用于确定腐蚀损失的传统试片法进行比较。结果表明,自补偿方法能够对温度波动进行补偿,并且通过超声技术测量的总厚度损失接近通过试样测量的值。最后,测量系统在暴露于阳光下的生产管道中进行了测试。结果表明，自补偿方法可以减少厚度损失读数中的振荡，由温度波动引起的，但是大的温度变化不能完全补偿。该实验还显示了低机械稳定性的影响，这导致了完全无效的结果。
