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附錄一 外文原稿：
Anhydrous Ammonia Pressure Vessels In The Pulp And Paper Industry
The purpose of this article is to ensure that pulp and paper operating companies, their engineering consultants, and inspection contractors are informed about stress corrosion cracking in anhydrous ammonia service. The information was written by a task group of the TAPPI Engineering Division Nondestructive Testing and Quality Control Subcommittee.
Bacteria in some activated sludge effluent treatment systems require supplementary food. In some cases, this food is provided by ammonia and phosphoric acid which are stored on the mill site. Ammonia is commonly stored as anhydrous liquid ammonia in carbon steel vessels at ambient temperature and 16 bar (250 psig) pressure.
These vessels can be subject to stress corrosion cracking (SCC).SCC could cause release of ammonia, which is a hazardous chemical. SCC of carbon steel vessels in anhydrous ammonia service is somewhat analogous to that experienced in continuous digesters. For example, the importances of stress relief during fabrication and of in-service inspection are common to both.
This article concerns storage in horizontal pressure vessels at ambient temperature, as this type of vessel is used in pulp and paper applications. Large refrigerated storage tanks are used for atmospheric pressure storage in the chemical industry.
History of Scc In Ammonia Storage Vessels
The history of SCC in carbon steel ammonia storage vessels was reviewed by Loginow (1) and is also briefly summarized in a NACE Technical Committee Report entitled “Integrity of Equipment in Anhydrous Ammonia Storage and Handling” (2). In the 1950s, liquefied ammonia began to be injected directly into soil for fertilization. Failure of carbon steel storage vessels by SCC began to occur. These failures were unexpected since liquefied ammonia had been used for many years in the refrigeration, chemical, and metal heat treating industries without reported problems.
Investigation confirmed SCC to be the cause of cracking. Three recommendations were made in 1962 that still form the basis of modern codes:
? Pressure vessels should be fully stress relieved.
? Extreme care should be used to eliminate oxygen from ammonia systems.
? Ammonia should contain at least 0.2% water to inhibit SCC.
Loginow reported that adoption of these recommendations practically eliminated SCC in carbon steel vessels in the agriculture industry. However, in a recent Western Canadian survey SCC was found in 100 of 117 field storage vessels inspected by wet fluorescent magnetic particle testing (WFMT) (3).
Despite the above measures SCC continued to occur in road transport tanks constructed from high strength steels, in refrigerated storage vessels and in vessels which had been weld repaired but not subsequently stress relieved. An additional recommendation to limit steel tensile or yield strength was embodied in the U.S. and British ammonia storage codes, respectively (4, 5).
? ANSI K61.1—Nominal tensile no greater than 70,000 psi (580 MPa)
? U.K. Code—Minimum specified yield strength shall not exceed 350 MPa (51,000 psi).
PRACTICAL CONSIDERATIONS
This article is concerned mainly with practical considerations important to pulp and paper mills already possessing anhydrous ammonia storage vessels or planning to fabricate such vessels. In view of the industry’s experience with SCC in continuous digesters the governing objectives should be to control fabrication and inspection to prevent, or at least minimize, in-service problems including over-reaction to relatively minor crack indications. Guidance is available in the published codes and detailed information is available from some ammonia suppliers.
Fabrication
The two main objectives in fabrication should be to provide the most crack resistant vessel possible at reasonable cost and to ensure that an adequate inspection baseline is available for interpretation of subsequent in-service inspections.
ASME Section VIII Division 1 does not require stress relief for anhydrous ammonia storage pressure vessels unless the owner specifies a lethal service designation.
The lethal service designation requires radiographic testing (RT) of all butt welded joints plus post weld heat treatment.
ANSI K-61.1-1989, “American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia,” adds several requirements:
? Fabrication to ASME Section VIII Division 1 Table UW 12 at a joint efficiency less than 80% is not allowed.
? Inspection and testing under UG-90(c) (2) (multiple, duplicate pressure vessel fabrication) is not allowed.
? Steel used for pressure containing parts shall have a nominal tensile strength no greater than 580MPa (70,000 psi).
? The minimum design pressure for ambient temperature storage shall be 16 bar (250 psig).
? Post weld heat treatment is mandatory and a furnace of sufficient size to accommodate the entire vessel is recommended. Welded attachments may be made to pads after post weld heat treatment.
? Horizontal vessels shall be mounted on saddles which extend over at least one third of the shell’s circumference. Thermal expansion and contraction shall be allowed for and means provided to prevent corrosion between the shell and the saddles.
The 1986 British Code “Storage of Anhydrous Ammonia under Pressure in the United Kingdom” requires:
? Steel must have specified minimum yield strength less than 350 MPa (51,000 psi).
? Weld filler must have minimal strength overmatch compared with the base plate.
? 100% magnetic particle inspection of all internal welds in order to provide a record against which all future inspections of the vessel can be assessed.
? No welding is permitted after stress relief without subsequent local stress relief.
? Concrete saddles are prohibited.
? Support must be on continuously welded steel saddles attached before stress relief.
Although the British Code does not state that magneti particle inspection should be by WFMT it is generally agreed that WFMT is the most sensitive technique and should be used for inspection of ammonia storage vessels. All inspection should be performed by qualified technicians. SNT-TC-1A Level II is a recommended minimum.
One pulp and paper company has added the following requirements for fabrication of such vessels:
? Incorporation of a “corrosion allowance” of at least 1.6 mm (1/16 in.) to permit minor defect chasing during in-service inspections and to provide a margin against pitting which may occur if water is allowed to enter an out of service vessel.
? All weld toes profiled by grinding prior to wet fluorescent magnetic particle testing (WFMT). All WFMT indications greater than 1.6 mm (1/16 in.) to be removed by grinding before post weld heat treatment.
? Shear wave ultrasonic testing (UT) of nozzle-to-shell welds permitted if RT is judged impractical.
? WFMT to be repeated after final hydrotest test of the vessel and the report retained by the owner.
? Vessel to be dried completely after hydrotest test and nitrogen padded until filled with ammonia.
Valves, piping, and fittings
Both the ANSI and U.K. codes address piping, valves, and fittings. A detailed summary is beyond the scope of this article, but some points are worth noting.
? ANSI K61.1 requires all nonrefrigerated ammonia piping to meet the requirements of ANSI/ASME B31.3 “Chemical Plant and Petroleum Refinery Piping.”
? The U.K. Code states copper and copper bearing alloys shall not be used.
ANSI/ASME B31.3 requires a minimum of 5% of piping welds be radiographically tested. Valves and other apparatus should be rated for ammonia service and should not contain copper or copper alloy components.
In one case, a nickel rupture disc corroded to failure at its periphery due to formation of an ammonia solution at a gasketed joint exposed to the weather.
In-service inspection
Vessel entry Liquid or gaseous ammonia is hazardous and in some jurisdictions release of ammonia vapor to the atmosphere is prohibited by law. Vessels must be properly purged by water and/or steam. Detailed procedures for vessel purging and entry are available from ammonia suppliers (6).
Inspection procedures The ANSI standard does not address in-service inspection but does state weld repair or alteration must conform to the current edition of the National Board Inspection Code (NBIC).
The 1992 edition of the NBIC includes nonmandatory guidelines for inspection of liquid ammonia vessels (7).
These guidelines recommend:
? Power buffing or light sandblasting as surface preparation for inspection
? All interior welds be examined by WFMT.
? Cracks should be removed by grinding without encroaching on the minimum thickness required by ASME Section VIII and the original design.
? Weld repairs, regardless of size, should be post weld heat treated wherever possible.
Light grinding does increase the sensitivity of WFMT compared to sandblasting or power buffing (8). For example the NBIC mandates grinding as surface preparation for deaerator inspection. The omission of grinding in the guidelines for ammonia vessel in-service inspection may be due to concern that rough grinding may produce residual stress sufficient to initiate SCC in anhydrous ammonia service. If welds have been properly profiled for WFMT on initial fabrication, then grinding for in-service inspection should not be needed.
The NBIC guidelines also state that other inspection methods such as acoustic emission or ultrasonics may be used and that fracture mechanics may be used to assess the integrity of vessels where complete 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 compressors 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 nitrogen-pad 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 recommends the following:
? WFMT inspection of 100% of all internal butt welds within the first three years of service
? WFMT re-inspection 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 in-service inspection techniques and frequencies. Each owner should determine inspection frequency in conjunction with the appropriate authority. Some jurisdictions require a 3-year inspection frequency.
SUMMARY
The use of carbon steel pressure vessels for storage of anhydrous ammonia in the pulp and paper industry could be a non-event 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 recommended 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; R.S. Charlton, Levelton Associates Consulting Engrs.; R.C. Faloon, MQSInspections Inc.; and W. E. Boudreau, Belle Testing Inc.
Literature cited
1. Loginow,A.W. , Materials Performance 25 (12): 18(1986).
2. NACE Technical Committee report 5A192, Integrity of Equipment in Anhydrous Ammonia Storage and Handling, Houston, NACE Storage Tank, Spokane, 1992.
3. Stephens, J. D. and Vidalin, F., 1994 AIChE Ammonia Symposium Notes, American Institute of Chemical Engineers, New York, p. 9.
4. Compressed Gas Association Inc., American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia ANSI K61.1-1989, Arlington, VA, 1989 (CGA Pamphlet G-2.1-1989).
5. Storage of Anhydrous Ammonia Under Pressure in the United Kingdom, London, Her Majesty’s Stationery Office, 1986. (Health and Safety Booklet HS/G 30)
6. Cominco Fertilizers (U.S.) Inc., Decommissioning an Ammonia Storage Tank, Spokane, 1992.
7. The National Board of Boiler and Pressure Vessel Inspectors, National Board Inspection Code: A Manual for Boiler and Pressure Vessel Inspectors, Columbus, OH, 1992, p.197.
8. Reid, J. C. and Reid, C., TAPPI 1992 Engineering Conference Proceedings, TAPPI PRESS, Atlanta, Book I, p.163.
9. Conley, M. J., Sture, A., and Williams, D., “Ammonia Vessel Integrity Program: A Modern Approach, 1990 AIChE Ammonia Symposium Notes, New York, AIChE, 1990.
10. Cominco Fertilizers (U.S.) Inc., “Commissioning an Ammonia Storage Tank”, Spokane, 1992.
附錄二 外文翻譯：
紙漿和造紙行業(yè)中的無(wú)水氨壓力容器
本文的目的是為了確保紙漿和紙張經(jīng)營(yíng)公司，他們的工程顧問(wèn)，承建商了解在脫水氨設(shè)備中的應(yīng)力腐蝕開裂現(xiàn)象。這篇資料是由美國(guó)紙漿與造紙工業(yè)技術(shù)協(xié)會(huì)無(wú)損檢測(cè)工程部和質(zhì)量控制小組委員會(huì)共同編寫。
細(xì)菌生存在一些活性污泥污水處理系統(tǒng)中需要充足的食物。在某些情況下，這種食品是氨和磷酸的儲(chǔ)存現(xiàn)場(chǎng)。氨通常以無(wú)水液氨的形式貯存在室溫和1.6MPa（250 磅）的壓力的碳鋼容器中。
這些容器可能會(huì)受到應(yīng)力腐蝕開裂（SCC）。應(yīng)力腐蝕開裂可能導(dǎo)致氨泄露，這是一種危險(xiǎn)化學(xué)品。用于無(wú)水氨設(shè)備的碳鋼容器中的SCC是有點(diǎn)類似于連續(xù)蒸煮罐的經(jīng)驗(yàn)。例如，減少壓力的引入在生產(chǎn)和在役檢查過(guò)程都是很常見(jiàn)的。本文關(guān)注在常溫下的臥式壓力容器，像這類型容器通常用于紙漿和造紙的應(yīng)用。大型冷藏儲(chǔ)罐在化工行業(yè)一般是常壓儲(chǔ)存。
SCC在氨儲(chǔ)罐的歷史
SCC在碳鋼氨儲(chǔ)存容器的歷史是由Loginow（1）審查通過(guò),也是在簡(jiǎn)要回顧了NACE技術(shù)委員會(huì)報(bào)告題為“完整的設(shè)備在無(wú)水氨的儲(chǔ)存和處理”(2)。在20世紀(jì)50年代，液氨作為肥料直接注入土壤。碳鋼貯存容器由于應(yīng)力腐蝕開裂而導(dǎo)致的故障開始出現(xiàn)。這些故障是意外，因?yàn)橐喊币延糜谠谥评?，化工多年，金??熱處理行業(yè)沒(méi)有報(bào)告的問(wèn)題。
調(diào)查結(jié)果證應(yīng)力腐蝕是開裂的原因。1962年提出了三條建議構(gòu)成了現(xiàn)代條例的基礎(chǔ)：
?壓力容器應(yīng)充分消除應(yīng)力。
?要特別小心是消除氨系統(tǒng)中的氧氣。
?氨應(yīng)該包含至少0.2％的水，以抑制應(yīng)力腐蝕開裂。
Loginow報(bào)告說(shuō)，采用這些建議能有效避免應(yīng)力腐蝕發(fā)生在農(nóng)業(yè)用碳鋼容器中。然而，最近的加拿大西部的調(diào)查顯示通過(guò)濕熒光磁粉探傷檢查（WFMT）（3）發(fā)現(xiàn)117處農(nóng)場(chǎng)的儲(chǔ)罐中有100處發(fā)生了應(yīng)力腐蝕開裂。
盡管采用了上述措施，SCC仍然發(fā)生在由高強(qiáng)度鋼建造的公路運(yùn)輸油罐、冷藏儲(chǔ)存容器以及作了焊接修復(fù)卻沒(méi)后續(xù)的應(yīng)力消除的容器。另外一條建議被納入美國(guó)和英國(guó)的氨儲(chǔ)存條例，以限制鋼材的拉伸或屈服強(qiáng)度。
?ANSI K61.1 -名義抗拉強(qiáng)度不超過(guò)70,000磅（580兆帕）
?英國(guó)條例指定的最低屈服強(qiáng)度不超過(guò)350兆帕（51,000磅）。
實(shí)用的考慮
本文主要關(guān)注是實(shí)際問(wèn)題對(duì)于已擁有無(wú)水氨貯存容器的紙漿和造紙廠或計(jì)劃制作這類容器的重要性。以連續(xù)蒸發(fā)罐中SCC的經(jīng)驗(yàn)來(lái)看，執(zhí)行目標(biāo)應(yīng)該是控制制造和檢驗(yàn)，以避免或至少減少在運(yùn)行中的問(wèn)題，包括過(guò)度反應(yīng)相對(duì)輕微裂縫的跡象。從一些氨的供應(yīng)商提供公開條例和規(guī)范資料可以得到相關(guān)的指導(dǎo)。
制造
制作中的兩個(gè)主要目標(biāo)應(yīng)是提為抗裂容器供合理的成本，并確保為后續(xù)在役檢驗(yàn)的解釋有適當(dāng)?shù)臋z驗(yàn)基線可用。
ASME第1部第VIII節(jié)沒(méi)有要求無(wú)水氨存儲(chǔ)壓力容器要應(yīng)力消除，除非擁有者指定了一個(gè)致命的部件名稱。
指定的致命部件需要焊接接頭的焊后熱處理加所有對(duì)接射線檢測(cè)（RT）。
美國(guó)國(guó)家標(biāo)準(zhǔn)化組織（ANSI）K – 61.1 - 1989，“美國(guó)國(guó)家標(biāo)準(zhǔn)無(wú)水氨的存儲(chǔ)和處理安全要求”增加了幾個(gè)要求：
?制造符合ASME第一部第VIII節(jié)UW12表的效率不能低于80％。
?基于UG-90(c)檢查和測(cè)試是不允許的。
?用于壓力容器部件的鋼材的標(biāo)稱抗拉強(qiáng)度應(yīng)當(dāng)不低于580MPa（70,000 psi）。
?室溫儲(chǔ)罐的最低設(shè)計(jì)壓力應(yīng)當(dāng)為16bar（250 psig）的。
?必須進(jìn)行焊后熱處理，要求足夠大的熔爐來(lái)適應(yīng)整個(gè)容器。附件的焊接點(diǎn)可能要進(jìn)行熱處理
?臥式壓力容器應(yīng)當(dāng)安裝在鞍座超過(guò)至少有一個(gè)殼體的周長(zhǎng)三分之一。應(yīng)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。
1986年英國(guó)章程“英國(guó)常壓無(wú)水氨儲(chǔ)存”要求：
?鋼材的指定最低屈服強(qiáng)度必須小于350兆帕（51,000磅）。
?焊接填充物的最小強(qiáng)度必須高于于比母材強(qiáng)度。
?100％的內(nèi)部焊縫磁粉探傷，對(duì)未來(lái)所有的容器檢查提供可以評(píng)估的紀(jì)錄。
?沒(méi)有后續(xù)局部應(yīng)力消除的應(yīng)力消除后允許無(wú)焊接
?混凝土鞍座是禁止的。
?鋼制鞍座連續(xù)焊接必須在應(yīng)力釋放之前。
雖然英國(guó)規(guī)范并沒(méi)有規(guī)定磁化粒子檢查應(yīng)當(dāng)進(jìn)行濕熒光磁粉實(shí)驗(yàn)，人們普遍認(rèn)為，WFMT是最靈敏的技術(shù)，應(yīng)該用于檢驗(yàn)氨貯存容器。所有的檢查應(yīng)該由合格的技術(shù)人員來(lái)完成。SNT-TC-1A II級(jí)是建議的最低水平。
其中紙漿和造紙公司已對(duì)這些容器的制造增加了下列要求：
?設(shè)立“腐蝕裕量”至少1.6毫米(1 / 16英寸)，允許在役檢驗(yàn)中出現(xiàn)的微小缺陷，并在容器停止服役期間浸水，對(duì)可能出現(xiàn)的腐蝕保持一定的裕度，。
?濕熒光磁粉探傷（WFMT）檢驗(yàn)所有焊接接頭前要進(jìn)行磨削。在焊后熱處理前，大于1.6毫米（1 / 16英寸）所有WFMT跡象要被磨削。
?如果射線探傷不符合實(shí)際，可以使用橫波超聲波檢測(cè)（UT）。
?容器水壓試驗(yàn)后重復(fù)進(jìn)行WFMT，由業(yè)主保留的測(cè)試報(bào)告。
?容器水壓試驗(yàn)后要完全干燥，并且進(jìn)行充氮保護(hù)直至填充氨。
閥門，管道及配件
ANSI和英國(guó)壓力容器規(guī)范都對(duì)管道，閥門和配件進(jìn)行了論述。詳細(xì)摘要已經(jīng)超出了本文的范圍，但有些要點(diǎn)是值得注意的。
?ANSI K61.1要求所有的非冷卻氨管道要滿足符合ANSI / ASME B31.3的規(guī)定“化工廠和石油精煉廠管道。”
?英國(guó)壓力容器規(guī)范規(guī)定銅及銅合金軸承不得使用。
ANSI / ASME B31.3要求5％以上管道焊縫需要X線測(cè)試。閥門和其他設(shè)備應(yīng)使用標(biāo)準(zhǔn)的的氨部件，并且不能含有銅或銅合金成分。
在一個(gè)案例中，一個(gè)鍍鎳爆破片腐蝕失效原因在于襯墊上的氨溶液的形成
在役檢查
容器引進(jìn)。液態(tài)或氣態(tài)氨是危險(xiǎn)化學(xué)品的，而且某些司法管轄區(qū)的法律禁止氨蒸氣釋放到大氣中。容器必須用水或蒸汽妥善清除。從氨供應(yīng)商獲取詳細(xì)的清洗和引進(jìn)說(shuō)明（6）。
檢查程序。 ANSI標(biāo)準(zhǔn)不??涉及在役檢查，但要求焊接修復(fù)或改裝，必須符合現(xiàn)行版國(guó)家檢測(cè)局規(guī)范（NBIC）。
該NBIC 1992年版包括液氨儲(chǔ)罐非強(qiáng)制性的檢查指導(dǎo)。
這些指導(dǎo)原則建議：
?拋光或噴砂表面處理為檢查做準(zhǔn)備
?所有的內(nèi)部焊縫進(jìn)行WFMT檢測(cè)。
?裂縫應(yīng)磨削處理以符合ASME第八節(jié)規(guī)定的最小設(shè)計(jì)厚度。
?焊縫，不論尺寸，都應(yīng)進(jìn)行焊后熱處理。
輕微磨削相對(duì)噴砂處理和電學(xué)拋光可以增加WFMT靈敏性相（8）。例如，NBIC要求磨削作為除氧檢測(cè)的表面處理的準(zhǔn)備。在氨儲(chǔ)罐的在役檢查指導(dǎo)中磨削的遺漏可能是由于擔(dān)心粗磨可能產(chǎn)生的殘余應(yīng)力以致產(chǎn)生應(yīng)力腐蝕開裂。如果在初始制造過(guò)程中焊縫因WFMT產(chǎn)生了合適的變形，那么在在役檢查中磨削就沒(méi)有必要了。
該NBIC準(zhǔn)則還規(guī)定，如可能使用聲發(fā)射或超聲波等檢查方法，斷裂力學(xué)可用于評(píng)估那里的容器完整性裂縫徹底清除是不實(shí)際的。
通常，腐蝕只發(fā)生在無(wú)水氨儲(chǔ)罐，是因?yàn)樵谕Ｖ惯\(yùn)行期間滲入水。淺點(diǎn)蝕已發(fā)現(xiàn)在有些容器底部的油性沉淀物。油源被假定為從用來(lái)處理氨的壓縮機(jī)。
針對(duì)由于容器引進(jìn)而產(chǎn)生的空氣污染問(wèn)題和磨削無(wú)損檢測(cè)產(chǎn)生殘余應(yīng)力的問(wèn)題，采用如聲發(fā)射技術(shù)和UT的技術(shù)可以由使用者考慮。英國(guó)規(guī)范并沒(méi)有提及常溫常壓容器的無(wú)損檢測(cè)，但指出了，如果聲發(fā)射檢測(cè)要用于球形儲(chǔ)存容器，應(yīng)當(dāng)在初始水壓試驗(yàn)采取相應(yīng)的參考。無(wú)損檢測(cè)應(yīng)用于其他行業(yè)。
儲(chǔ)罐填充。應(yīng)該為因檢查而清空的容器填充建立一個(gè)安全規(guī)程。這對(duì)于凈化容器空氣防止發(fā)生應(yīng)力腐蝕開裂是非常重要的。從氨供應(yīng)商獲取詳細(xì)說(shuō)明（10）。如果容器在檢查后沒(méi)有被立刻送回返修，然后應(yīng)注意干燥，并有可能氮封它取決于停止服役的時(shí)間。
檢查頻率。無(wú)論是ANSI文件或NBIC沒(méi)有處理檢驗(yàn)頻率。英國(guó)規(guī)范建議如下：
?在首三年服役期WFMT100％檢查所有內(nèi)部的對(duì)接焊縫
?如果在兩年內(nèi)發(fā)現(xiàn)重大缺陷進(jìn)行重新檢查，
?繼無(wú)發(fā)現(xiàn)明顯缺陷后，后續(xù)的任何檢查應(yīng)對(duì)所有T型接頭和的對(duì)接焊縫總長(zhǎng)度的10％進(jìn)行WFMT檢測(cè)
?在任何情況下后續(xù)檢查的時(shí)間間隔超過(guò)6年。
從上述可以很明顯看出在役檢查技術(shù)和頻率存在一定范圍。每個(gè)使用者應(yīng)與結(jié)合相關(guān)部門確定檢查頻率。有些管轄區(qū)需要3年的檢查頻率。
總結(jié)
對(duì)紙漿和造紙工業(yè)的碳鋼無(wú)水氨儲(chǔ)存壓力容器的使用可能是一個(gè)非活動(dòng)或進(jìn)入檢查和維修的惡性循環(huán)。本文重點(diǎn)關(guān)注的是應(yīng)力腐蝕開裂。從ANSI和英國(guó)規(guī)范，NACE文件，氨儲(chǔ)罐供應(yīng)商和現(xiàn)行的技術(shù)文獻(xiàn)可以獲取的大量有關(guān)注意事項(xiàng)的信息。在美國(guó)化學(xué)工程師學(xué)會(huì)（AIChE）舉行的年度合成氨安全研討會(huì)旨在發(fā)現(xiàn)在安全生產(chǎn)，運(yùn)輸和儲(chǔ)存氨及相關(guān)化學(xué)品的方法。這些專題討論的會(huì)議記錄AIChE公開發(fā)表。它建議任何此類容器的所有人應(yīng)及時(shí)了解當(dāng)前的專業(yè)知識(shí)。
里德材料和麥克米蘭布勒德爾研究，4225金凱德街，本拿比，BC，加拿大V5G 4P5腐蝕科科長(zhǎng)。
工作組成員：克雷格里德; R.S.查爾頓Levelton協(xié)會(huì)咨詢工程部。R.C. Faloon鋼筋混凝土s公司和W. E. Boudreau檢測(cè)公司
參考文獻(xiàn)：
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