Insights from BCC Research

New Ultrasonic Probe Tests Zinc Thickness in 450°C Molten Metal

Posted by Clayton Luz on Jul 12, 2017 10:00:00 AM

In the nondestructive testing (NDT) equipment and services industry, methods are employed to monitor the integrity of the structure through its life. These NDT methods supplement other techniques, which can be applied without interruption to normal operation of a structure or a machine. Known as condition monitoring, these techniques represent continuous progress in the development and application of NDT methods.

Ultrasonic NDT is one type of conditional monitoring technology that characterizes the thickness or internal structure of a test piece through the use of high frequency sound waves. The technique offers many advantages, including maintain the integrity of the test piece, which does not have to be cut, sectioned, or exposed to harmful chemicals. The technique requires access to only one side of the test piece, unlike with mechanical thickness tools like calipers and micrometers. And, unlike with radiography, there are no health hazards with ultrasonic testing. Most favorably, test results are highly repeatable and reliable.

Recently, a new probe technology emerged that can conduct safety critical testing inside galvanizing kettles equipment that are loaded with molten zinc at 450°C. Using a zinc immersion probe (ZIP), the technique accurately measures the thickness of kettles although the probe is immersed in 450°C molten metal.

The ZIP was developed by the Sonemat, a spin-out company formed in 2005 by two University of Warwick scientists who specialize in non-contact ultrasonic nondestructive testing. In 2014, Sonemat and Zinco UK signed an agreement to use the ultrasonic probe technology.

The galvanizing process involves the immersing chemically cleaned steel products into the zinc kettle to provide corrosion protection and long life. Galvanizing kettles need to be checked periodically to monitor rates of corrosion throughout the equipment in order to avoid a catastrophic molten zinc spillage. Those corrosion wear rates vary depending on volumes, dip sizes and the amount of production at each plant.

Previous monitoring techniques were either using external probes or galvanizers had to actually drain the zinc from the kettles to another device or the kettle was then left to cool to the point at which physical sampling of the kettle surface could be undertaken.

The technique, which offers minimal downtime because the zinc remains in the kettle and the service can be performed outside production hours, can measure up to 3.1 meters deep, with measurements accurate to +/- 1.5mm, the companies claim.

According to David Watkins, Zinco managing director, the ZIP probe technology has been used to measure galvanizing kettles in Africa, Malaysia, Middle East, Scandinavia and Europe.

“We are confident that this new resource will lead to us serving at least 30% of the world-wide market this safety critical testing,” Watkins says. “There are around 3,000 galvanizing kettles around the world that can potentially benefit from using this type of inspection probe that not only provides significant safety data as well as maximizing investment return of equipment." 

The global market for NDT equipment and NDT services, which totaled more than $15.8 billion in 2016, is expected to increase to more than $17.2 billion and $26.4 billion in 2017 and 2022, respectively, says a new report published by BCC Research.

The June report also projects an 8.9% CAGR for the combined market for NDT equipment and NDT services from 2017-2022. Notably, the report calls for the ultrasonic immersion testing technology market to demonstrate a 9.1% CAGR.

Topics: Manufacturing