3 Effective NDT Ultrasonic Pipeline & Piping Inspection Methods

When it comes to pipeline inspections, ultrasonic testing (UT) is the best tool available for nondestructive testing (NDT) personnel. Depending on the variation, UT can detect active or passive corrosion, among many other problematic corrosive anomalies. However, inspectors need additional tools and equipment, such as eddy current testing or UT scanners, to probe certain segments of a pipeline after long-range UT testing.

The good news is that technicians can test any type of pipeline using NDT, no matter how large or small. Regardless of the infrastructure, it’s important to choose NDT UT products that conform to the shape and welding type of the pipelines. When it comes to pipeline NDT, the three most important techniques to keep in mind include long-range ultrasonic testing (LRUT), phased array ultrasonic testing (PAUT), and scanning.

Using LRUT for Long-Range Detection

It’s worth noting that long-range UT should only be used as a general guiding mechanism that highlights major and minor flaws. LRUT is an innovative inspection strategy that assesses pipes from long distances, but it has several drawbacks. Limited detection capability prevents it from pinpointing the exact location of corrosion or cracking within the pipeline, and it cannot assess the type of damage detected (e.g. active vs. passive corrosion).

However, LRUT is the most effective way to analyze long sections of piping from a distance and test hard-to-reach locales. It’s also viable enough to reach buried pipelines, including underwater infrastructure. After a long-range test, NDT specialists must procure specialized approaches, such as PAUT, to get a true sense of pipeline maintenance status. Tailored NDT designs will discover specific flaws throughout piping welds and appraise the exact nature of the flaw itself.

PAUT for Austenitic Alloys and Stainless Steel

Austenitic weld inspection within the oil and gas industry is one of the most important assets for professionals in this field. But the inspection process can be daunting without the right equipment. Austenitic alloys and stainless steel resist corrosion more than other materials but are not impervious to corrosive degradation. Therefore, NDT inspectors must implement the same rigorous NDT standards on austenitic alloys and stainless steel as any other item.

The best way to test stainless steel and austenitic alloys is via PAUT using 2D matrix array probes. Stainless steel materials carry anisotropic coarse-grain content, with each grain causing reflections and high noise levels. The high noise levels result in greater feedback issues during conventional testing processes versus PAUT. Also, NDT specialists must deal with unintended variations within the structure of the pipeline, making testing difficult.

When inspecting an austenitic weld, for example, NDT operators can use the 2D matrix probes in the following ways:

• Lowering frequencies between 1.5 MHz to 3.5 MHz for thicker components
• Multiple channel configuration of focal laws to obtain wider coverage of the weld
• Use steering in the passive plane to capture additional flaws.

The 2D capacity of the array allows users to angle wave beams throughout the testing stage, providing comprehensive beam coverage that canvases additional areas. A 2D matrix device can also find axial and circumferential flaws, especially awkwardly-positioned defects that could escape detection. A 2D probe yields added convenience and flexibility, but users can get the same resilience through NDT scanning equipment that can probe different welding types.

Pipeline Scanning

Overall, NDT scanning has several advantages, such as:

• Wall thickness measurements
• Sensitivity to surface flaws and subsurface flaws
• Stellar flaw detection of minor defects
• Measurement and identification of the defects

There are a variety of NDT scanning methods, but one of the most impressive items on the market is a weld scanner. It also provides a sweeping scan on different welds, including real-time data in UT form. A weld scanner is an all-around capable machine that works in confined and open spaces, as the scanner’s magnetic wheels conform to circumferential and axial welding. It’s also a viable option for technicians who must analyze certain pipeline subsections after long-range testing.

Weld scanners are one of the best products within the NDT UT industry. Moreover, NDT professionals should search for UT NDT items that can probe surface levels and subsurface levels.

There are also handheld corrosion scanning devices that adapt to flat and curved surfaces. These devices are the best in the industry at detecting erosion, pitting, and corrosion. They will also acclimate to small and large pipelines regardless of contortion or curvature.

For instance, inspectors can use a hand-held scanning brush to diagnose specific flaws after a LRUT. These instruments are portable enough to use with a single hand, and they encompass a wider scanning radius than standard UT. Certain scanners have special encoded wheels that track the scanning position, producing complete data of a test subject’s profile.  

Innovative Ultrasonic Pipeline Inspection Methods

Depending on the scenario, ultrasonic pipeline inspection requires multiple tools and instruments to obtain thorough data. But the investment in impeccable equipment is worth the money, as companies will maximize the lifespan of company assets and prevent operational failures that could devastate oil and gas campaigns.

Even though long-range scanning provides detection benefits, companies need custom inspection strategies that will detect all types of corrosion or cracking. Ultrasonic equipment is not only an excellent investment that preserves a safe atmosphere for workers, but it also safeguards the public from oil pipeline spills and leaks that endanger nearby communities.

Zetec provides some of the best instruments and tools that energy companies need to streamline operations. For more information on UT items and accessories, contact Zetec today to further customize NDT inspection procedures.