According to CSA Standard W59, at what distance from the weld must the minimum preheat be maintained in 44 mm thick plate?

• A. 25 mm
• B. 50 mm
• C. 100 mm
• D. 75 mm

Answer: (D)

Maintaining the minimum preheat temperature over a certain distance from the weld helps control cooling rates and hydrogen diffusion in thick base metal, which reduces the risk of hydrogen-induced cracking. CSA W59 defines how far from the weld that preheat condition must be kept for different plate thicknesses. For a plate about 44 mm thick, the standard specifies that the preheat must be maintained out to 75 mm from the weld. This larger heated zone matches the greater heat-affected region in thicker material, ensuring the metal stays above the critical temperature long enough to minimize hardness and cracking during welding and initial cooling. The other distances correspond to different thickness ranges, but for 44 mm, 75 mm is the required distance.