The excellent combination of properties such as higher strength-to-weight ratio and excellent resistance to corrosion, makes titanium alloys attractive for many industrial applications.

Purified terephthalic acid (PTA) plants rely on titanium cladded vessels owing to its excellent corrosion resistant properties that stand up to the harsh, acidic environment in PTA chemical process.

Many fabricators use manual GTAW process for titanium welding owing to the ease of operation & low cost of investment.

In recent years, there is an increasing trend of mechanization for such joints to ensure right quality and improved productivity for large number of joints. Typically, mechanization is aimed with conventional GTAW process.

During recent times, few welding machine manufacturers offer GTAW welding power source with Keyhole technique to achieve full penetration in low thickness joint in single pass.

Recently, L&T manufactured several Ti cladded vessels which involved large number of low thickness Ti joints for nozzle liners with 4 mm and 10 mm thickness. These joints required full penetration with RT examination and bright silver colour in visual examination.

Several trials were undertaken by varying welding parameters and trailing & purging gas arrangements to achieve specified quality requirements. Subsequently, welding procedure was qualified wherein welded samples were subjected to various NDEs such as visual examination, dye penetrant test and radiographic test and destructive tests viz. tension test, bend test, hardness evolution, macro, and micro examination.

After completion of welding procedure qualification, Keyhole GTAW technique was successfully implemented for large number of welded joints.

This article is shared by Ajay Patel, Karan Modi, Anshuman Lal and Ritesh Patel.