The Case of the Defective Welds in Tower Arms
Cracks and defects in tower arm welds were observed during installation in the field. Welding HSLA steel of tower arms differs from welding ordinary steel.
Welds of 15 tower arms were assessed for the type of High Strength Low Alloy (HSLA) base metal steel in the pole and mounting brackets, HAZs and welds. Defects and cracks were found in the HAZs, steel and weld regions.
Factory welding procedures for HSLA steels require specific validation of the essential variables for predictable weld properties and to avoid cracking. Adverse thermal effects can result from welding with insufficient preheat. Heat input and maximum interpass temperatures must be controlled for each type and thickness of HSLA steel.
Weld defects in the tower arms originated both on the outside and inside of the arm pole. The owner lost revenue from installation delays and spent millions of dollars for repair/replacement of arms due to defective shop welding.
The Lesson Learned:
Welding tower arms to mounting brackets requires specific and proven welding practices. Improper welding can result in welding defects and cracked HSLA steel plate. Proven welding procedures, certified welders and AWS-Certified Welding Inspectors should be used 100% while welding with strict adherence to established codes.