This study evaluated the performance and condition of a combined water-tube and fire-tube boiler system. The boiler, with a design capacity of 20 t/h, has been in operation since 2011 and utilizes a circulating fluidized bed (CFB) combustion system fueled by low-grade coal. The assessment included visual inspection, material thickness measurements, ultrasonic testing of weld joints, non-destructive testing (Dye Penetrant Testing), hardness testing, and in-situ metallography. The objectives of the assessment were to determine the extent of wall thinning due to corrosion, erosion, or creep; to identify defects in the boiler material and welds through non-destructive testing; to assess metallurgical and mechanical degradation caused by thermal aging, overheating, fatigue, creep, stress corrosion cracking (SCC), or other degradation mechanisms; and to evaluate the current condition and estimate the remaining life of the boiler to determine whether it is still serviceable, repairable, or requires replacement or depressurization. The assessment results indicated that the boiler frame, fire tube, water tube, pipe sheet, and header were in good condition. Visual inspection revealed minor rust and dirt but no significant defects. Material thickness measurements met the Maximum Allowable Working Pressure (MAWP) requirements, and hardness tests showed no significant changes in material properties. Non-destructive testing (NDT) and in-situ metallography confirmed no material degradation or structural changes. Recommendations include cleaning the surfaces of the fire tube and water tube, ensuring boiler feedwater meets required standards to prevent corrosion, reinstalling previously blocked water tubes, repairing external corrosion and damaged insulation on the header, and repairing cracked and peeling refractory walls in the furnace. Furthermore, it is recommended to conduct a boiler assessment every five years to ensure continued reliability and safety. This comprehensive assessment aims to provide baseline data for making informed decisions regarding repairs, replacements, and optimization of the boiler system to improve its performance and ensure compliance with safety regulations. The findings and recommendations from this study are critical to maintaining the operational efficiency and safety of the boiler, thus supporting a sustainable and efficient production process.