A Study On Austenitic Boiler Tube Wall Oxide Skin Accumulation Measurement Technology

For a long time, oxide skin exfoliating of superheater and reheater was a major cause that block off the tubes and make turbine erosion.At present domestic and foreign inspection method to basically have two kinds:one is the traditional ray, the two is through the magnetic measurement to determine the approximate amount of accumulation of oxide skin.On the rube by ray, this method is time-consuming, laborious, long testing period. Using magnetic measurements in the detection of oxide skin accumulation drawback is the presence of a small amount of oxide skin is not sensitive, requires a certain accumulation amount, and affected by magnetic of the inner wall oxide skin, poor detection stability, poor repeatability.The main factor of the oxide skin exfoliating, accumulation and blockage in tube is not the accumulation amount or stacking quality, and is mainly a stacked oxide skin accounts for the tube cross-sectional area.As in the cutting of the tube inspection found oxide accumulation reached 180 grams, but not over temperature tube. While some tube pile weight only 30 grams, there are tubes tissue temperature phenomenon, so the measurement of oxide stacking height that is important, but the magnetic measurement method cannot meet the requirements.At present domestic ultra (ultra) supercritical unit of heating surface tube of substantial use of stainless steel.With the steam parameter increase, the shedding of skin packing problems become more prevalent, the problem will seriously affect the unit safety level and unit utilization.The solution to this problem is the brook no delay. The primary measure is to develop a precise measurement of oxide stacking height instrument, using the shutdown or maintenance time for rapid measurement of time, and the existence of stacked tube, clear in time, avoid tube burst caused unplanned outage, thus the ultra (ultra) supercritical unit safe and reliable operation of power grid operation stability to have very important sense.In this study. Huadian Zouxian Power Company Limited sampling pipe of superheater and oxide simulation experiments, the corresponding data obtained after the relationship Huadian Zouxian Power Company Limited # 5 unit superheater, reheater, and other power generating units testing applications, and cutting pipe test data and verify the actual accumulation of correspondence. View from the field inspection, oxide stack height and phase changes into a single value corresponding to the relationship.In this paper, the eddy current technology in austenitic boiler tube wall measure the accumulation of oxide on the application. This design and development of a boiler tube wall austenitic oxide accumulation measurement system used for in-service boiler heating surface of the tube wall austenitic off oxide accumulation measurement, and austenitic stainless steel to achieve the accumulation of oxide object orientation, qualitative,quantitative detection of stack height. The system uses ultra-low-frequency eddy current testing methods, qualitative and quantitative probe, by measure the thickness of accumulation oxide to analyze the impact of security of the pipe run.