1、海洋工程錨鏈營運檢驗指南 目錄 TOC o 1-5 h z 1適用范圍12檢驗間隔期、目的和范圍13錨檢查34錨轉環檢查35錨鏈檢查衡準 36導鏈器和錨機的檢查一錨鏈系統57導纜器和絞盤的檢驗一鋼絲繩系統 68錨鏈附件的檢查69鋼絲繩的檢驗810參考文獻1011適用范圍本指南適用于擬按照船級社關于海上移動式平臺要求入級的定位錨泊系統 的檢查。臨時錨泊設備應按船級社鋼質海船入級規范進行檢驗1。2檢驗間隔期、目的和范圍2.1年度檢查的間隔期為12個月。檢驗進行時，平臺應位于作業吃水狀態，定位錨泊系統處于使用狀態。2.1.1年度檢查目的是確認錨泊系統在下一次年度檢驗前能繼 續實施其預定的用途。年度檢

2、驗不應妨礙平臺作業。如可行，年度檢驗應在重新就位遷移過程中進行。2.1.2年度檢驗范圍限于絞盤或錨機附近的錨泊部件。根據平臺上可見到的錨泊部件，應對下述情況給予特別注意：錨鏈一掣鏈器和錨機鏈輪凹槽（以下簡稱“鏈槽”）處錨鏈肩部的磨耗；一鏈環在錨機鏈槽中的支撐狀況。鋼絲繩變平的鋼絲繩；一斷絲的鋼絲繩；磨耗殆盡或腐蝕的鋼絲繩。驗船師應根據平臺作業記錄判定在過去的12個月內錨泊系統是否出現諸如：斷絲、機械損傷、連接卸扣松動以及錨鏈或鋼絲繩跳線等情況。如果年度檢驗表明可見的錨鏈或錨索損傷嚴重或對其管理疏忽，則應擴大檢驗范圍。凡發現以下典型損傷須進行更為全面的檢驗：錨鏈鏈徑減少超過4%；橫檔脫落；1可參

3、照中國船級社鋼質海船入級規范相關要求執行。2R4級以上錨鏈的橫檔松動；一會引起錨鏈損傷的已磨損錨鏈輪（即錨機滾筒）磨耗。鋼絲繩一明顯的變平或面積減少；會引起鋼絲繩損傷的已磨損絞纜桶；嚴重的磨耗或腐蝕；一斷絲。2.2特別檢驗特別檢驗的間隔期為5年，其檢驗范圍更為廣泛，通常應在遮蔽水域內進行。船級社認為必要時，可縮短兩次特別檢驗的間隔期。2.2.1假定在間隔期內錨泊系統已得到 合適的保養和維修，特別檢驗目的是確保在下一次特別檢驗前每根錨鏈能按其預定用途正常作業。2.2.2特別檢驗項目應包括: 人所有錨鏈連接處的近觀檢查（100%），必要時應予以清潔；入擴大的、有代表性的無損探傷檢驗：5%，普通錨鏈

4、20%，有導纜器作用超過5年的錨鏈所有連接卸扣人尺寸校核，檢驗長度須超過5個鏈環。2.2.3應對下述情況給予特別注意：人自上次檢驗以來在平臺作業中與錨機和導鏈器經常接觸的錨鏈（或鋼絲 繩）部位。驗船師應確信上述部位的錨鏈仍適宜在錨機和導鏈器處使用。人連接卸扣的松動程度和銷鎖緊裝置布置。入全部錨機和導鏈器鏈槽應注意：鏈槽的異常磨耗或損傷；鏈槽磨耗速率，包括鏈環與鏈槽間相對磨耗率；鏈環和鏈槽的不匹配及在鏈槽中不適當的支撐。人在起放錨操作中的錨泊系統的功能試驗，并特別注意：鏈環和/或鋼絲繩及連接卸扣在錨機和導鏈器槽上平滑通過；3無跳鏈或其他不規則情況。2.2.4應對約1%的鏈環測量其厚度（直徑）。選

5、取的鏈環應 大致均勻分布在錨鏈工作段中。若外觀檢驗結果表明惡化程度過分/極少；則上述檢驗比例可予以增加/減少。2.2.5所有已使用4年以上的肯特型和螺栓型連接卸扣均應予以拆開， 并按8.2要求對所有的機加工表面進行磁粉檢查。2.3替代特別檢驗的循環檢驗作為特別檢驗的替代方法，業主可選擇進行循環檢驗。此方法系指在岸上額外準備一根同等規格系泊纜，在每年度或其他合適的時間，通過輪流交 替方法，能將到檢驗周期的系泊纜循環回收陸地檢驗。3錨檢查應檢查錨冠、錨爪和錨桿的損傷，包括裂紋和彎曲。應檢查錨卸扣銷和錨冠銷，若發現磨損或彎曲過大應予以更換。可動錨爪應能在錨冠停止點之間轉動自 如。彎曲的錨爪或錨桿應根

6、據批準的工藝規程加熱和適當的校正，其后還應進行 磁粉檢查。4錨轉環檢查雖然轉環已不再普遍采用，但由于嚙合轉環螺母螺紋的腐蝕已造成錨的失落。此類螺紋應予以仔細檢查，若發現有嚴重的腐蝕，則轉環應予以去除或更換。5錨鏈檢查衡準5.1所考慮的錨鏈類型本節僅適用于橫檔是按下述方法之一固定的“海洋工程”或“石油平臺級”錨鏈：人鏈環閃光對接焊附近機械壓牢和另一端填角焊（例如IACS R3級鏈）1人橫檔兩端均為機構壓牢就位（例如IACS R4級鏈）2 其他類型的錨鏈應予以特別考慮。1IACS R3級鏈相當于CCS材料與焊接規范中R3級錨鏈，下同。2IACS R4級鏈相當于CCS材料與焊接規范中R4級錨鏈，下同

7、。4海工錨鏈服役環境要比常規船錨鏈的服役環境更惡劣。海工錨鏈遭受作業載荷的作用時間也較長。海水中循環載荷的長期作用將加大幾何和冶金缺陷對疲勞壽命的不利影響。此外，從統計觀點而言，海工錨鏈鏈環數量的增多將使錨鏈更 易于破壞。由于“缺口”效應（例如鏈環上橫檔置入凹槽），高強度鋼（如IACS R4級錨鏈所采用的鋼材）的疲勞強度與靜拉伸強度比值要比典型的低強度鋼低（如IACS R3級 錨鏈所采用的鋼材）。5.2磨損和腐蝕引起鏈環直徑減少鏈徑測量應在鏈環彎曲部位和任何嚴重磨耗或銹坑區域上進行。應對與錨機或導鏈器鏈槽正常接觸的肩部給予特別注意。最小橫剖面面積小于原始名義面積90%的鏈環應予以廢棄。若允許修

8、復，則 應由合格人員按照批準的工藝規程進行修理。注：對IACS R4、R4S和R5級錨鏈，不允許進行焊接修理（見5.3.1）。鏈徑減少5%等價于原始橫剖面面積減少10%。應相隔90進行兩次鏈徑測量，并將平均鏈徑測量值與原始鏈徑（扣除允許的設計余量）進行比較。5.3錨 鏈橫檔缺陷的修復或更換橫檔在鏈收放過程中將防止鏈打結或扭曲，并在承載時支撐兩側以減少拉伸和彎曲應力，以延長疲勞壽命。橫檔脫落是不能接受的。脫落橫檔的鏈環應予以去除或按認可的工藝規程重新安裝橫檔。5.3.1 一端由填角焊固定的橫檔如果橫檔松動或焊縫出現裂紋，則橫檔可能脫落。橫檔若有任何軸向或側向移動是不能接受的，該鏈環必須修復或更換

9、。鏈環不允許在閃光對接焊端焊接橫檔。在橫檔閃光對接焊端處橫檔和鏈環間的間隙超過3mm （ 1/8英寸）的鏈環應考慮予以報廢。如被允許，采用重新進行填角焊來閉合間隙的方法可予以考慮。應盡可能避免有裂紋焊縫的現場修理，如必須進行此操作，應由具備相應資 質的人員按認可的工藝規程施焊。注：對IACS R4、R4S和R5級錨鏈，不允許施焊修理。橫檔兩端均靠機械壓牢就位的錨鏈僅能按認可的機械“擠壓”橫襠復位工藝規程予以修復。不允許在橫檔兩端施焊，在鏈環閃光對接焊縫鄰近的橫檔端也不允許施焊。現有的兩端焊接的橫檔需要特別考慮，并應進行專門的裂紋探測檢查。一般將要5求降低閃光對接焊縫處的力學性能，并須經沿岸國主

10、管部門的批準。5.3.2靠壓入配合和機 械鎖緊的橫檔錨鏈橫檔是否松動過大難以定量。應依據驗船師對錨鏈總體情況的判定，確定拒絕或是接受帶有松弛橫檔的錨鏈。軸向移動為1mm或更小的橫檔時可以接受的。軸向移動大于2mm的鏈環必須予以“擠壓”修理或去除。軸向移動為12mm的鏈環是否允許使用必須根據平臺作業海域的環境條件和下次錨鏈檢查的預期期限而定。不超過4mm的橫檔側向移動是可接受的。5.4鏈環修理裂縫、凹坑和其他表面缺陷（不包括焊縫裂縫）可經打磨去除，只要鏈徑的最終減少不超過5%D（ D為鏈徑）以及橫剖面面積（由于腐蝕、磨耗和打磨引起面積減少）不少于原始名義面積的90%。橫剖面面積應按相隔90測量兩

11、個 直徑的最小平均值計算。表面缺陷不能靠打磨去除的鏈環應予以更換。5.5鏈環的更換有缺陷的鏈環應予以去除，并用連接卸扣（即連接鏈環）遵照下述良好的海 事實踐予以更換：人替換連接卸扣應符合IACS W22或API 2F的技術要求1；人連接卸扣應在水平面內通過導鏈器和錨機。因為連接卸扣的疲勞壽命比普通鏈環低很多，因此應盡可能地減少使用。平均而言，兩個連接卸扣至少應相隔122m（ 400英尺）；如果大量鏈環應予報廢且此類鏈環分布在整根錨鏈中，則該根錨鏈應以新鏈 替換。6導鏈器和錨機的檢查一錨鏈系統6.1導鏈器檢查應驗證所有導鏈器在其正常操作必需的全部運動范圍內均能繞各自的1相當于CCS材料與焊接規范

12、第1篇第10章第3節要求。6Z軸轉動自如。所有螺栓、螺母及其他用于固定導鏈器的零部件均應予以檢查， 必要時應予以更換。導鏈器與船體的連接應經驗證，必要時需進行無損探傷檢查。注：存在著由于固定螺栓螺紋腐蝕造成導鏈器軸上封板的松動，并導致導鏈器設備嚴重損傷及使鏈和導鏈 器跳動的情況。因此應檢查固定螺栓以保證如果導鏈器處犧牲陽極系統不起作用，螺栓材料仍不會先 腐蝕。6.2錨機應特別注意錨機的掣動能力，應檢查掣鏈器及將載荷傳遞給平臺結構的路徑，并驗證其堅固性。6.3鏈槽和錨鏈支撐位于鏈槽內的鏈環應僅在其四個肩部區域與導鏈器相接觸，以避免鏈環內出 現危險的彎曲應力。對錨鏈支撐的可靠性應予以驗證，必要時鏈

13、槽的過大磨損應予以修理，以防 止進一步損傷錨鏈。錨槽可按由導鏈器/錨機制造廠提供的標準工藝規程焊補。一般，鏈槽的硬 度應比鏈環稍低，其焊補工藝規程必須是針對所用的錨鏈等級。7導纜器和絞盤的檢驗一鋼絲繩系統7.1導纜器見6.1。7.2絞盤應對絞盤的掣動能力，以及棘爪、棘輪行剎車設備的操作性予以特別關注。將合成載荷至平臺結構的路徑的堅固性應予以驗證。鋼絲繩在絞盤卷筒上的合適排列應予驗證并使驗船師滿意，需要時將調整卷 筒和排纜機構。8錨鏈附件的檢查8.1 一般要求 錨卸扣、大的無擋鏈環、轉環和連接鏈環應進行外觀檢驗。某些部位應進行磁粉探傷檢查。待檢區域應在每個附件上打上清楚的標記。需要時鏈環和附件應

14、予以拆開。損傷的附件按現場驗船師的要求應予更換。標明有關區域的圖例可在API RP 21， 圖6中找到。7需作磁粉檢查區域的一般性指南如下所述：一大的無檔鏈環：大的無檔鏈環的內接觸面；一錨卸扣：內接觸面和銷；一轉環：轉環銷、嚙合螺紋和嚙合面。8.2連接卸扣（連接鏈環）8.2.1實際情況說明， 因為連接卸扣的失效，出現了一定數量的未到期錨和鏈丟失現象。因此，對于沒有等效證明文件，且用在高強度錨鏈上的連接卸扣，例如ORQ （采油設備質量等級）及其以上等級1，檢驗應予特別關注。8.2.2磁粉檢查 所有使用超過4年的肯特型或類似型式連接卸扣都應拆卸進行磁粉檢查，API RP 2I圖7 給出了檢查區域圖

15、示位置。需作磁粉檢查區域的一般性指南如下所述：人連接卸扣本體：所有鏈環扣加工面和打磨面以及鏈環彎曲部分的側面；人連接卸扣橫檔：僅扣加工面；人連接卸扣銷：100%。8.2.3疲勞被認為是衡量加工表面的關鍵衡準。在其它類型表面上， 外形應打磨光滑，并在打磨完工后即刻進行磁粉檢查。通常，打磨完工后所形成冊槽的 半徑最小為20mm，沿鏈環輪廓線的凹槽長度應大于或等于其深度的6倍。注：磁粉撿查前噴砂可損傷機加工面，故應予以避免。應采作其他清潔方法。最大許用打磨深度為5%的公稱鏈徑。由于局部打磨和全部腐蝕磨耗的組合效應，打磨修理處最小允許橫剖面面積為90%的名義橫剖面面積。由于局部打磨和全面腐蝕磨耗的組合

16、效應，打磨修理處最小允許直徑為95%的公稱鏈徑。8.2.4全面腐 蝕/磨耗由于均勻腐蝕磨耗所導致的最小允許橫剖面面積為90%名義橫剖面面積（等價于直徑均勻減少5%）。8.2.5將連接鏈環的兩個半環鎖緊在一起的錐銷在其兩端應與鏈 環接觸良好；錐銷大頭上的鉆孔凹孔應塞入鉛條并錘緊塞牢以防止錐銷松動。1ORQ級相當于CCS材料與焊接規范海上設施系泊定位用錨鏈R級。8 8.2.6重拼裝后的松動性任何重拼裝后松動的肯特型或類似型式的連接卸扣須視具體情況作專門考慮后才可予以接受。注：拼裝面之間的松動將大大降低連接卸扣的剩余疲勞壽命。沿橫檔縱向超過0.5mm的橫檔移動也可能大大降低連接卸扣的剩余疲勞壽命。9

17、鋼絲繩的檢驗9.1接受衡準接受衡準可從ISO標準4309得到。進一步的詳細說明還可從API RP 2I，圖18和19給出的報廢指南中得到。應注意ISO標準4309主要適用于起重設備，其安全系數可能比錨泊鋼纜 高。驗船師在闡明鋼絲繩狀況中應極其小心。狀況明顯時接受或拒絕是比較容易的。但兩種狀況之內的“灰色”區域是難于評估的。驗船師必須根據所有獲得的證據作出正確的評估和技術判斷。通常，鋼絲繩的服役年限或時間，除了作為驗船師在確定檢驗范圍時應考慮的一個因素外，對接受或拒絕鋼絲繩并沒有直接的關系。9.2檢驗和檢查應進行100%的外觀檢驗和直徑測量。9.2.1外觀檢驗應對每根鋼絲繩錨腿驗證和記錄下述 項

18、目：一斷裂鋼絲的性質和數量；接頭處鋼絲斷裂情況；外部磨耗和腐蝕；鋼絲斷裂的集中程度；變形；股斷裂；接頭面積；鋼絲繩直徑的減少，包括繩芯破斷或擠出。9.2.2直徑測量應以約100m的間距進行， 并應由現場驗船師來決定。如果發現特別值得注意的部位，檢驗可集中在這些部位上，并應以更小的間距進行直9徑測量。9.2.3如果在下層部位中表明存在嚴重的內部腐蝕或繩芯的可能斷裂或鋼絲破斷，應視實際可能性進行內部檢查。作為鋼絲繩內部檢查的指南，見API RP 21，3.3.6.3。9.3鋼絲繩損傷指南鋼絲繩失效原因可從所見到的鋼纜損壞中推出。鋼絲繩失效的大部分類型簡述如下。包括圖像實例在內的，較詳細的資料可從I

19、SO標準4309和API RP 2I獲得。9.3.1接頭處破斷的鋼絲表示其接頭處存在高應力，這可能由接頭安裝錯誤、疲勞、過載、或敷設、回收過程中的操作錯誤等所造成分散型破斷鋼絲，由API RP2I圖912可表明其破壞的原因。繩股頂處冠部斷裂或單根鋼絲的破斷可由過大的張力、疲勞、磨耗或腐蝕所造成。過大的張力可由鋼絲斷口的頸縮所表明。疲勞由斷裂面垂直于鋼絲軸線所表明。腐蝕和磨耗可由鋼絲橫剖面的減少所表明。兩股界面處谷部斷裂表示繩股繃緊，通常由破斷的繩芯或使繩芯直徑減少的 內部腐蝕所造成。谷部斷裂可能由高的載荷、緊的滑輪和相對于鋼絲繩直徑顯得太小的滑輪所造成。局部集中在單根股或相鄰股中的斷裂鋼絲可因

20、局部損壞所造成。一旦形成，此種損傷通常將持續惡化。9.3.2鋼絲繩直徑的變化可由外部磨耗、鋼絲間或股 間磨損、拉伸或腐蝕所造成。鋼絲繩直徑的局部減少可表明繩芯斷裂。相反，鋼絲繩直徑的增加可表明腐蝕導致繩芯脹大。9.3.3鋼絲繩外層股冠部處磨耗可根據腐損部位由與導纜器、平臺結 構或海床間摩擦所造成。鋼絲繩內各股間或各根鋼絲間的內部磨損是由互相摩擦造成的，并因鋼絲繩彎曲和腐蝕加速磨損。9.3.4腐蝕減少橫剖面面積從而降低鋼絲繩強度，腐蝕會招致應力 裂紋的不10規則表面從而加快疲勞。腐蝕可由下述情況表征：人導纜器處鋼絲繩直徑將變小；人靜止不動鋼絲繩直徑實際上將增大，是因外層股下銹蝕所致。對系泊纜，直

21、徑增大是很罕見的。9.3.5變形，即鋼絲繩已出現與其正常結構不同的變化，可引起繩中 不均勻的應力發布。紐結、彎曲、摩擦、斷裂和變平是鋼絲繩通常的變形。稍有變形鋼絲繩的強度損失不大。嚴重的變形可加快鋼絲繩的退化，并導致過早的破壞。9.3.6熱損壞， 雖然它在錨泊鋼纜正常營運中很少發生，仍可用變色來表明。對由過高或過低溫度造成的損壞應給予及時的注意。除了已知非常低的溫度對潤 滑劑會產生有害的影響外，其對鋼絲繩的其他影響尚不清楚。10 參考文獻10.1鋼絲繩API RP2I和ISO標準4309。(關于ISO標準，見9.1)10.2錨鏈API RP2I“浮式鉆井平臺錨泊部件營運檢查的推薦標準”。No.

22、38Page 1 of 9 IACS Rec. 1995/Rev.1 2010No.38(cont)Guidelines for the Survey of Offshore MooringChain Cable in UseApplication and PurposeThe information herein is intended to provide guidance to Surveyors for inspection of position mooring systems which have been classed by the Society for Mobile Off

23、shore Drilling Units. Temporary mooring equipment is to be surveyed under the Rules for Building and Classing Steel Vessels of the Classification Society.Survey Interval, Purpose and ExtentAnnual Surveys are to be conducted at approximately twelve (12) month intervals, with the vessel at operational

24、 draft, with the position mooring system in use.The purpose of the Annual Survey is to confirm that the mooring system will continue to carry out its intended purpose until the next annual survey. No disruption of the units operation is intended. Ideally, the Annual Survey would be done during a rel

25、ocation move.The scope of the Annual Survey is limited to the mooring components adjacent to the winch or windlass. Depending on the mooring component visible from the unit, particular attention should be given to:Chain-Wear on the chain shoulders in way of the chain stopper and windlass pockets;-Su

26、pport of chain links in the windlass pockets.Wire Rope-Flattened ropes;-Broken wires;-Worn out or corroded ropes.The surveyor should determine if any problems have been experienced in the previous twelve (12) months period with the mooring system, e.g. breaks, mechanical damage, loose joining shackl

27、es, chain or wire jumping.If the Annual Survey reveal severe damage or neglect to the visible part of chain or cable, a more extensive survey should be performed.Typical damage warranting a more comprehensive survey could be:Chain-Reduction in diameter exceeding 4%;-Missing studs;-Loose studs in Gra

28、de 4 chain;-Worn out cable lifters (i.e. gypsies) causing damage to the chain.Wire Rope-Obvious flattening or reduction in area;-Worn cable lifters causing damage to the wire rope;-Severe wear or corrosion;-Broken wires.No.38(1995)(Rev.1Oct2010)No.38Page 2 of 9 IACS Rec. 1995/Rev.1 2010No.38(cont)Sp

29、ecial Periodical Surveys are carried out at intervals of approximately five (5) years and will require extensive inspection, usually associated with a sheltered water visit. When considered necessary by the Society, the interval between Special Periodical Surveys may be reduced.The purpose of the Sp

30、ecial Periodical Survey is to ensure that each chain is capable of performing its intended purpose until the next Special Periodical Survey, assuming that appropriate care and maintenance is performed on the mooring system during the intervening period.The Special Periodical Survey should include:Cl

31、ose visual examination of all links of mooring chains, with cleaning as requiredEnhanced representative NDT sampling-5% on general chains-20% on chain which has been in way of fairleads over last five (5) years-All connecting linksDimension checks, including length over five (5) linksParticular atte

32、ntion should be given to:Those lengths of chain (or wire rope) which have frequently been in contact with the windlass and fairleads during the units operation since the last survey. The Surveyor should ensure that these lengths are rated for use in the way of the windlass and fairlead.The looseness

33、 and pin securing arrangements of the joining-shackles.All windlass and fairlead chain pockets for:-Unusual wear or damage to pockets;-Rate of wear on pockets, including relative rate of wear between links and pockets;-Mis-match between links and pockets, and improper support of the links in the poc

34、kets.A functional test of the mooring system during anchor-handling operation for:-Smooth passage of chain links and/or wire rope and joining-shackles over the windlass and fairleads pockets;-The absence of chain jumping or other irregularities.The thickness (diameter) of approximately 1% of all cha

35、in links should be measured. The selected links should be approximately uniformly distributed through the working length of the chain. The above percentage may be increased/decreased if the visual examination indicates excessive/minimal deterioration.All joining-shackles of the Kenter type and bolte

36、d type which have been in service for more than four (4) years should be dismantled and an MPI performed on all machined surfaces as per 8.2.No.38Page 3 of 9 IACS Rec. 1995/Rev.1 2010No.38(cont)Special Continuous SurveysIn lieu of a special periodic survey, the Owner may opt for a Continuous Survey,

37、 by providing an extra mooring line which may be regularly inspected on shore and exchanged with lines installed on the unit on an annual or other appropriate schedule.Anchor InspectionThe anchor head, flukes and shank should be examined for damage, including cracks or bending. The anchor shackle pi

38、n and crown pin should be examined and renewed if excessively worn or bent. Moveable flukes should be free to rotate between stops on the anchor head.Bent flukes or shanks should be heated and jacked back in place according to an approved procedure, followed by Magnetic Particle Inspection.Anchor Sw

39、ivelsAlthough swivels are no longer in common use, anchors have been lost due to corrosion of the threads engaging the swivel nut. These threads should be carefully examined and, if significant corrosion is found, the swivel should be removed or replaced.Chain Inspection CriteriaChain Types Consider

40、edThis section applies only to Offshore or Rig Quality chains with studs secured by one of the following means:Mechanically locked adjacent to the links (IACS R3 chain for example) flash-butt-weld and fillet welded on the other endStuds mechanically locked in place on both ends (IACS R4 chain for ex

41、ample) Other types of chain will require special consideration.The service environment of offshore mooring chain is more severe than the service environment for conventional ship anchoring chain. Offshore chain is exposed to service loads for a much longer period of time. The long term exposure to c

42、yclical loadings in sea water magnifies the detrimental effect of geometric and metallurgical imperfections on fatigue life. Moreover the increased number of links in offshore chains renders the chain more susceptible to failure from a statistical standpoint.Due to the effect of notches, e.g. the st

43、ud footprint, higher strength steels, such as that used for IACS R4 chain, have a lower ratio of fatigue strength to static tensile strength than typical lower strength steel such as used for IACS R3 chain.Chain Link Diameter Loss due to Abrasion and CorrosionDiameter measurements should be taken in

44、 the curved or bend region of the link and at any area with excessive wear or gouging. Particular attention should be given to the shoulder areas which normally contact the windlass or fairlead pockets.No.38Page 4 of 9 IACS Rec. 1995/Rev.1 2010No.38(cont)Links with minimum cross-sectional area less

45、than 90% of the original nominal area should be rejected. If repair is permitted, it should be done by qualified personnel using an approved procedure.Note: WELD REPAIR IS NOT PERMITTED ON IACS R4, R4S and R5 CHAIN (See paragraph 5.3.1)A 5% reduction in diameter is equivalent to 10% of the reduction

46、 in cross-sectional area to original.Two diameter measurements should be taken 90 degrees apart and the average compared with original diameter considering with allowable diminution.Chain Stud Defects and Repair or ReplacementStuds prevent knots or twist problems during chain handling and support th

47、e sides of the links under load to reduce stretching and bending stresses, resulting in longer fatigue life. Links with missing studs should be removed or the studs should be refitted using an approved procedure.Chain Studs Secured by Fillet Welds on one EndThe stud is likely to fall out if it is lo

48、ose or the weld is cracked.Any axial or lateral movement is unacceptable and the link must be repaired or replaced. Links with studs fillet welded on the flash-butt-weld end of the stud are unacceptable. Rejection of links with gaps exceeding 3 mm (1/8 inch) between the stud and the link at the flas

49、h-butt-weld end of the stud should be considered. Closing the gap by renewing the fillet weld may be considered, where permitted.Field repair of cracked welds should be avoided. Welding must be performed by qualified personnel using approved procedures.Note: WELD REPAIR IS NOT PERMITTED ON IACS R4,

50、R4S and R5 CHAIN Chains with studs mechanically locked in place on both ends may only be repaired by an approved mechanical squeezing procedure to reseat the stud.Fillet welding of studs on both ends is not acceptable nor is welding on the stud end adjacent to the links flash-butt-weld.Existing stud

51、s with fillet welds on both ends will require special consideration and will be subject to special crack detection efforts. A reduction in mechanical properties in way of the flash-butt-weld will normally be required and approval of the coastal Administration may also be required.Chain Studs Secured

52、 by Press Fitting and Mechanical LockingIt is very difficult to quantify excessive looseness of chain studs. The decision to reject or accept a link with a loose stud must depend on the surveyors judgment of the overall condition of the chain complement.Axial movement of studs of 1 mm or less is acc

53、eptable. Links with axial movement greater than 2 mm must be repaired by squeezing or removed. Acceptance of chain links with axial movements from 1 to 2 mm must be evaluated based on the environmental conditions of the units location and expected period of time before the chain is again available f

54、or inspection. No.38Page 5 of 9 IACS Rec. 1995/Rev.1 2010No.38(cont)Lateral movement of studs up to 4 mm is acceptable.Link RepairsCracks, gouges and other surface defects (excluding weld cracks) may be removed by grinding provided the resulting reduction in link diameter does not exceed 5% and the

55、crosssectional area, due to abrasion, wear, and grinding is at least 90% of the original nominal area. Cross-sectional area should be calculated for the lowest average of two diameters taken 90 degrees apart.Links with surface defects which cannot be removed by grinding should be replaced.Chain Link

56、 ReplacementDefective links should be removed and replaced with joining-shackles, i.e. connecting links, guided by the following good marine practice:The replacement joining-shackle should comply with IACS W22 or API 2F.Joining-shackles should pass through fairleads and windlasses in the horizontal

57、plane. Since joining-shackles have much lower fatigue lives than ordinary chain links as few as possible should be used. On average, joining-shackles should be by 122 m (400 ft) or more apart.If a large number of links meet the discard criteria and these links are distributed in the whole length, th

58、e chain should be replaced with new chain.Fairlead and Windlass Inspection - Chain SystemsFairleadsInspection should verify that all fairleads move freely about their respective Z-axes, to the full range of motion required for their proper operation. All bolts, nuts and other hardware used to secure

59、 the fairlead shafts should be inspected and replaced, as required.Fairlead attachment to the hull should be verified and NDT conducted, as necessary.Note: There have been cases of closing plates on the fairlead shaft coming loose due to corrosion of the threads of the securing bolts, resulting in s

60、erious damage to the fairlead arrangements and the complete jamming of the fairlead and chain.Consequently, the securing bolts should also be checked to ensure that the bolt material does not corrode preferentially, should the sacrificial anode system fail to function in way of the fairlead.Windlass