老舊熱風爐設備適用性評估

Fitness Assessment on a Used Hot Blast Stove

本文說明某熱風爐舊設備的再適用性，該熱風爐已運轉滿32年後將進行更新，為了節省成本，將保留蓄熱室胴體殼板為設備更新的一部分。中鋼腐蝕測試中心對熱風爐胴體殼板作劣化與再用狀況評估，作為採取維修措施的依據。研究試驗結果顯示，依據API579計算各區殼板所需的最小厚度，遠小於實際厚度；最大容許工作壓力MAWP約為設計壓力的3倍以上。經歷32年的使用，殼板主要的腐蝕劣化型態為局部腐蝕、熱點與應力腐蝕，殼板減薄量少，仍有很長的使用壽命。舊殼板、銲道與新殼板的疲勞限度遠大於膜應力，適用於疲勞的環境。並可依據裂紋穩定成長方程式，估算它的裂紋成長速率。

This article describes the fitness of a used hot blast stove. The hot blast stove had been used for 32 years, and a renovation was to be implemented. For saving the cost, the checker chamber of the shell will be retained as part of the renovated equipment. In order to establish a maintenance basis, China Steel Corrosion Test Center evaluated the degree of deterioration and the residual life of the hot blast stove. Test results showed that the actual thickness of each zone of the checker shell estimated from API579 was much larger than the minimum required thickness. The maximum allowable working pressure based on its current thickness was approximately more than three times the designed operating pressure. After a 32-year service, it was found that the corrosion forms of the checker shell included localized corrosion, hot spot cracking, and stress corrosion cracking. Thinning of the checker shell was not significant, and the continuing service life was expected to be very long. The fatigue stress thresholds of the old plate, the weld bead, and the new plate were all higher than that of the operating membrane to be used in the renovated hot blast stove. They were therefore suitable to be used in fatigue environments. In case of a crack, its growth rate may be estimated from a theoretical crack growth equation.