Nondestructive testing method for peel-off of oxidation layer on inner wall of boiler tube

Abstract

The invention discloses a nondestructive testing method for peel-off of an oxidation layer on the inner wall of a boiler tube. The method comprises the following steps: coating a polished point with a coupling agent, using a high frequency probe to be in contact with a to-be-detected point, catching an interface wave between the oxidation layer on the inner wall of the boiler tube and a metal layer, displaying the thickness transmission sonic path distance of an oxide skin on the inner wall of the boiler tube of the detected point by an oscilloscope, and after the testing, converting the measured sonic path distance by the oscilloscope into the thickness value of the oxide skin on the inner wall. If the measurement result differences of the thickness values of the oxide skin on the inner wall are larger when the probe is moved within a small range near the to-be-detected point, the oxidation layer of the point is indicated to be peeled off.

Description

technical field [0001] The invention belongs to the technical field of non-destructive detection and diagnosis, and relates to a non-destructive detection method for peeling off of an oxide layer on the inner wall of a boiler tube. Background technique [0002] Thermal power plant units operate in a high-temperature environment for a long time. Since the high-temperature boiler tubes are under high pressure and the operating temperature is within the creep temperature range, the main form of damage is high-temperature creep. With the prolongation of running time, a dense oxide layer will be formed on the inner wall of the tube, and its composition is mainly Fe 2 o 3 and Fe 3 o 4 , The oxide layer increases the heat transfer resistance of the metal tube wall, which cannot effectively cool the tube wall, which leads to an increase in the temperature of the tube wall metal and accelerates the oxidation process of the tube wall metal. Under the condition that the steam outle...

AI Technical Summary

Problems solved by technology

[0009] X-ray technology has made great progress in recent years. It has been developed to detect the thickness and peeling of the inner wall of the steel pipe by filming. However, when the oxide scale is thin, it is difficult to measure accurately.

In addition, the instrument is expensive, the work efficiency is low, and the ray radiation is harmful to the human body, which limits the ray detection to a certain extent.