Evaluation, Reporting and Trending of Ultrasonic Thickness Data From Recovery Boiler Inspections

Introduction

The American Paper Institute Recovery Boiler Reference Manual, Volume 1, October 1979, indicates that the two main goals of conducting ultrasonic thickness (UT) inspections are to determine (1) the current tube wall thickness and (2) the rate of tube wall metal wastage.

The analysis of tens of thousands of UT readings from black liquor recovery boilers is an intimidating and time-consuming task. When a graphical presentation of the UT data in its correct relative position is used, it makes digesting the thousands of bits of data a much easier task. Problem areas in the boiler are easily identified and many engineering hours of labor are saved. The graphical presentation permits the quality (accuracy and consistency) of the UT data to be carefully examined.

When the UT data is analyzed over time, a tube wall metal wastage rate (wear rate) may be developed. However, due to the quality of UT data, great care must be exercised when using wastage rates for maintenance and planning activities. This paper will explain these ideas and discuss the accuracy and consistency of the UT data TCRI has processed.

For fifteen years, TCRI has focused on the evaluation, reporting, and trending of UT data gathered from black liquor recovery and power boiler inspections to give an accurate evaluation of the inspection. The mill engineer needs accurate information so the correct maintenance decisions can be made. As a quality assurance company, it is important to prepare an unbiased analysis of the UT data. We have processed UT data from more than 390 recovery boiler inspections. Maintenance and operations depend upon accurate data for maintenance planning and operational reliability.

The Technical Database System (TDS) is a software program that could not have been developed without heavy client participation. Approximately 60% of the evaluation options in the program were created from requests/ input from owner users. The mathematical logic and rule bases used in the program have been reviewed by mathematicians and statistical experts, and have been thoroughly tested. Because we are a quality assurance company and NOT a nondestructive testing lab, the software has been designed to find potential inaccuracies, if there are any, with the UT readings that come from boiler inspections.

UT Data Reporting and Evaluation

To fully understand the results of a recovery boiler UT inspection, the mill engineer must accurately interpret large quantities of data. Each UT reading may be viewed as a piece of a very large puzzle. Assembling the puzzle can be very difficult, especially with the time constraints of a shutdown. We have created a graphical presentation of the data where as many as 35,000 UT readings can be displayed on one print, which simplifies and expedites the process. The graphical presentation permits all the UT data for an entire wall or section of the boiler to be examined at once.