【正文】 ion methods such as acoustic emission or ultrasonics may be used and that fracture mechanics may be used to assess the integrity of vessels where plete removal of cracks is not practical. Normally the only corrosion that occurs in anhydrous ammonia vessels is due to water ingress during out of service periods. Shallow pitting, however, has been found in the bottom of some vessels beneath oily deposits. The source of oil is presumed to be from pressors used to handle the ammonia. In view of concerns over air contamination due to vessel entry and residual stress imparted by grinding nonintrusive inspection, techniques like acoustic emission and UT could be considered by vessel owners. The British Code does not mention nonintrusive inspection of ambient temperature pressure vessels but does state that, if acoustic emission is to be used for spherical storage vessels, a reference base should be taken during initial hydrotesting. Nonintrusive inspection is being used in other industries (9). Vessel refilling Safety procedures should be established for refilling a vessel that has been emptied for inspection. It is also very important to purge the vessel of air to prevent the occurrence of SCC. Detailed instructions are available from ammonia suppliers (10). If a vessel is not to be returned to service immediately after inspection, then care should be taken to dry it and possibly nitrogenpad it depending on the time it will remain out of service. Inspection frequency Neither the ANSI document nor the NBIC deals with inspection frequency. The British Code remends the following: ? WFMT inspection of 100% of all internal butt welds within the first three years of service ? WFMT reinspection within 2 years if significant defects are found ? Subsequent to no significant defects being found, any subsequent inspection should include WFMT of all Tee junctions and 10% of the total length of butt welds ? In no case should the subsequent examination interval exceed 6 years. It is apparent from the above that latitude can exist for inservice inspection techniques and frequencies. Each owner should determine inspection frequency in conjunction with the appropriate authority. Some jurisdictions require a 3year inspection frequency. SUMMARY The use of carbon steel pressure vessels for storage of anhydrous ammonia in the pulp and paper industry could be a nonevent or deteriorate into a cycle of inspection and repair. This article has highlighted major concerns related to SCC. There is a wealth of additional information available on all considerations related to these vessels from the ANSI and British Codes, the NACE document, ammonia suppliers, and the current technical literature. The American Institute of Chemical Engineers (AIChE) holds the annual AIChE Ammonia Safety Symposium aimed at finding ways to safely manufacture, transport, and store ammonia and related chemicals. The proceedings of these symposia are published by AIChE. It is remended that any owner of such vessels keep aware of current expertise. Reid is materials and corrosion section head with MacMillan Bloedel Research, 4225 Kincaid St., Burnaby, BC, Canada V5G 4P5. Task group members: Craig Reid。氨通常以無水液氨的形式貯存在室溫和（ 250 磅）的 壓力的碳鋼容器中。 在 20世紀 50 年代，液氨作為肥料直接注入土壤。然而， 最近的加拿大西部的調查顯示通過濕熒光磁粉探傷檢查（ WFMT）（ 3）發(fā)現(xiàn) 117 處農(nóng)場的儲罐中有 100 處發(fā)生了應力腐蝕開裂。 ASME 第 1 部 第 VIII 節(jié) 沒有 要求無水氨存儲壓力容器要應力消除，除非擁有者指定了一個致命的部件名稱。應允許熱膨脹和收縮和給出以防止殼體和鞍座之間腐蝕的方法。 SNTTC1A II 級 是建議的最低水平。詳細摘要已經(jīng)超出了本文的范圍，但有些要點是值得注意的。從氨供應 商獲取詳細的清洗和引進說明（ 6）。例如， NBIC要求磨削作為 除氧檢測的表面處理的準備。英國規(guī)范并沒有提及常溫常壓容器的無損檢測，但指出了，如果聲發(fā)射檢測要用于球形儲存容器，應當在初始水壓試驗采取相應的參考。無論是 ANSI 文件或 NBIC 沒有處理檢驗頻率。在美國化學工程師學會（ AIChE）舉行的年度合成氨安全研討會旨在發(fā)現(xiàn)在安全生產(chǎn)，運輸和儲存氨及相關化學品的方法。 [3] 斯蒂芬斯， JD 和 Vidalin， F， 1994 年 AIChE 氨研討會報告，美國化學工程師協(xié)會，紐約， P， 9。