Question 105Steam Plants - Assistant Engineer

The correct answer is B) pressure buildup in the tube. When a water-tube boiler tube becomes sagged, a hole should be made in the tube prior to plugging it. This is done to prevent pressure buildup in the tube, which could lead to a catastrophic failure. If the tube is simply plugged without the relief hole, pressure could build up behind the plug, potentially causing the tube to rupture. The other answer choices are incorrect because they do not address the primary concern of pressure buildup, which is the key reason for making the relief hole.