INTRODUCTION

On insulated pipes, in order to perform PMI (Positive Material Identification), the joint welds under the insulation have to be located. Rather than expensive and time consuming stripping of the insulation, welds can be located in an inexpensive and rapid manner using an appropriately configured X-Ray real time imaging device.

These devices are quick to deploy, simple to operate and have a minimum safety requirement.

When welds have been located, a small area of insulation, such as a 4 inch diameter hole, can be removed to expose the pipe material either side of the weld and the weld itself. An X-ray portable Alloy Analyzer provides information on these three areas of interest.

THE TECHNOLOGY

The technique uses a 50 to 120 kV. X-Ray source and an Xraydetector/CCD camera (Figure 1) to image the profile of the weld under insulation (Figure 2); this enables the operator to mark the surface of the insulation within 0.25” of the center of the weld. The technique has also been shown to be extremely accurate in measuring the width of corrosion under insulation (Figure 3). It has been successfully applied to pipes with diameters up to 36 inch and with up to 5.5 inches of insulation, including asbestos (Figure 4)

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The portable Alloy Analyzer (Figure 5) uses xray fluorescence to obtain the chemical analysis of the material under test within 5 seconds.

The analyzer is simple to use and is capable of identifying over 20 standard elements and more than 200 common alloys of these elements. The analyzer can also be set up to provide a pass/fail indication.

With the additional heat shield (Figure 5/1), the analyzer can be used on surfaces up to 1000° F.

In PMI use, the front of the analyzer is brought into contact with the material to be tested, (Figure 6) the trigger held for a few seconds until the analyzer indicates that the test is finished and the result read from the built in screen. (Figure 7)

 

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The analyzer is also a bar code scanner - locations can be bar-coded and the analysis has the barcode information attached to the data. The highly durable barcode labels are permanently attached to the test sites and can provide future reference locations.

Positive Material Identification (PMI) can be carried out quickly, cleanly and safely, with a minimum amount of insulation removal, by using real time x-ray equipment and techniques. As surface temperatures up to 1000° F. can be accommodated, most surveys can be carried out with process plant fully on-line.

 

Features such as the barcode reader, integrated into the detector, prevents incorrectly recorded information while the ability to connect directly to a computer and download the data, increases efficiency and makes the data immediately available to other software for analysis or reporting.