Which inspection method is indicated for checking details on welded areas in cyclic temperature operation?

The selection of magnetic particle or liquid penetrant testing as the inspection method for checking details on welded areas in cyclic temperature operations is based on the ability of these methods to detect surface and near-surface discontinuities that can occur due to thermal cycling.

Welded joints in pressure vessels may experience fatigue and cracking as a result of the expansion and contraction caused by fluctuating temperatures. Magnetic particle testing is highly effective in revealing surface and slightly subsurface defects, such as cracks and inclusions in ferromagnetic materials. Liquid penetrant testing complements this by being suitable for a variety of non-magnetic materials, allowing it to uncover minute surface cracks and defects that could compromise the weld integrity.

In contrast, thickness gauging primarily measures wall thickness and does not provide information about surface defects, making it less suitable for this particular purpose. Visual inspection, while important, may not detect small, critical cracks that can cause failure under stress. Electro-chemical analysis focuses on the chemical composition of the material rather than the mechanical integrity of the welds, thus lacking relevance in identifying structural issues in welded areas due to thermal stresses.

By choosing magnetic particle or liquid penetrant testing, inspectors can ensure a more thorough assessment of weld integrity in environments subject to cyclic temperature variations