本文以老舊鍋爐為對象，綜合不同之評估方法，探討該鍋爐是否尚可繼續使用。所使用之評估方法包括：(1) 非破壞檢查、(2) 金相組織評估方法、(3) API 579 潛變損傷剩餘壽命評估、(4) 高溫氧化壽命評估及(5) 減薄之趨勢等。經由現場檢測及上述剩餘壽命研究分析結果顯示(1) 非破壞檢查未發現有明顯異常之設備、(2) 現場金相組織觀察皆未發現有晶界微孔洞存在，設備壽命消耗分率應在50%以下、(3) 以API 579 part 10 Level 1 及Level 2之Ω參數法評估結果，所有爐管潛變損傷分率皆小於0.25，設備可繼續使用、(4) 以高溫氧化腐蝕速率計算分析其可用年限，研判正常狀況下此種腐蝕現象對鍋爐之壽命影響尚小及(5)歷年測厚趨勢圖顯示爐管減薄程度很低。由分析結果顯示該鍋爐爐管因其使用溫度低、內部壓力小，使得組織之劣化等都相當小，雖然已超過其設計壽命年限，但狀況良好應可再使用一段期間。

A major concern for boiler users is whether the service time of an aged boiler having exceeded or approaching its design life could be prolonged or not. This paper presents assessment methods for investigating the suitability of aged boilers for prolonged operations. The methods we
used to evaluate the current condition and the remaining life of a boiler system included nondestructive testing (NDT) inspections, remaining life assessment in reference to metallography,life assessment based upon API 579 creep damage, remaining life due to high temperature oxidation, and the thinning trend of tube thickness. According to in situ inspections and the remaining life studies, there were several major findings. No anomalies in the boiler system were observed via the NDT inspections. No voids were found at the grain boundaries of the materials by the replica method, and the consumed service time might be below 50% of the expected life time of the boiler. The assessment results obtained by methods of API 579 Level 1 and Ω parameter Level 2 showed that the fraction of creep damage in all tubes was smaller than 0.25, indicating that the boiler system could still be put into service. In view of the high temperature corrosion rate, we found that the effect of high temperature corrosion on the tubes’ thickness was small. Data of historical thickness measurements showed that thinning of the tubes was small. The analysis results demonstrated that the degradation of the tubes was low, due to the low service temperature and internal pressure. Therefore, the condition of the boiler system was good enough to run for a period of time although the service life had exceeded the design life.