A boiler is a closed vessel where the combustion heat is transferred to the water until hot water or steam is formed. The failure occurred on the boiler water tubes at the textile processing plant, after an eight-year operation, which experienced damage like water tubes rupture in position at the bottom of the furnace boiler. In this position, the boiler water tubes directly received heat from burning coal. Damage occurred on the water tubes starting from a permanent form change until the rupture of the box (water tube boiler). The testing results of the boxes’ chemical composition, the boiler, failed and the matter degraded, such as; C, Mn, Ni, Cr, Ti, Mo, and Cu, which will reduce the physical and mechanical properties of the material of the tubes. Analysis of the results obtained by visual observation showed the tube’s box’s fish mouth, and this indicated overbooking on the tubes. The test results showed that the hardness of tubes in the damaged tubes has lower hardness than undamaged tubes. Under these conditions, the damaged tubes experienced softening (annealing). This is corroborated by the testing results of the tensile strength, which indicated that the tensile strength of the damaged tubes decreased compared to the undamaged tubes. Microstructures tubes’ microstructures ruptured tubes experienced a change from ferrite and pearlite became pearlite spheroidizing at grain boundaries. This differs from the microstructure on the intact tubes’ material, namely in the form of ferrite pearlite with a fine grain