台灣複循環電廠進氣霧化管線之動態應力分析與冷作彎管綜合效益評估 (Dynamic Stress Analysis and Comprehensive Benefit Evaluation of Cold Bending Methods for Inlet Fogging Piping in Taiwan Combined Cycle Power Plants)

/ Uncategorized / 作者:

摘要 / Abstract

在台灣能源轉型政策的推動下，再生能源的佔比逐年攀升，然而其間歇性發電特性也使得電網的「鴨子曲線」現象日益顯著。為維持電網頻率的穩定與供電可靠度，大型燃氣複循環發電廠（如大潭、通霄、興達等）必須承擔極為關鍵的基載與尖載調節任務。面對台灣亞熱帶氣候的夏季高溫，燃氣渦輪機的進氣空氣密度往往大幅下降，進而嚴重折損發電效率與最大出力。為克服此一物理限制，現代複循環機組廣泛導入「進氣霧化冷卻系統」（Inlet Fogging System），藉由高壓水霧的蒸發潛熱顯著降低進氣溫度，以達到提升出力的目的。 Driven by Taiwan’s energy transition policy, the proportion of renewable energy has been increasing year by year; however, its intermittent generation characteristics have made the grid’s “duck curve” phenomenon increasingly prominent. To maintain grid frequency stability and power supply reliability, large combined cycle power plants (CCPPs) (such as Datan, Tongxiao, and Hsinta) must undertake critical baseload and peak-load regulation tasks. Facing the summer high temperatures of Taiwan’s subtropical climate, the inlet air density of gas turbines often drops significantly, severely compromising power generation efficiency and maximum output. To overcome this physical limitation, modern combined cycle units widely adopt the “Inlet Fogging System,” significantly reducing inlet temperature through the latent heat of evaporation of high-pressure water mist to achieve output enhancement.

儘管該系統在熱力學上的效益顯著，但其附屬的高壓純水管線系統卻面臨嚴峻的工程挑戰。在機組頻繁啟停（Start-Stop）與負載急遽升降的運轉模式下，管線長期承受劇烈的水錘效應（Water Hammer）與流體暫態震動，極易於幾何不連續處引發疲勞破壞。此外，由於台灣多數大型電廠位處西海岸，管線系統長年面臨高氯離子鹽霧的侵襲，使得材料的冶金抗腐蝕能力成為決定系統壽命的另一關鍵。 Although the system offers significant thermodynamic benefits, its auxiliary high-pressure pure water piping system faces severe engineering challenges. Under the operational mode of frequent start-stops and rapid load fluctuations, the piping chronically endures severe water hammer effects and fluid transient vibrations, making it highly susceptible to fatigue failure at geometric discontinuities. Furthermore, since most large power plants in Taiwan are located on the west coast, the piping systems are continuously exposed to high-chloride salt spray, making the metallurgical corrosion resistance of the material another critical factor determining the system’s lifespan.

本研究報告旨在全面且深入地評估進氣霧化冷卻系統高壓管線之應力特徵，並提出具體可行的工程最佳化方案。在力學分析維度，本研究徹底屏棄傳統 ASME B31.1 與 B31.3 附錄 D 的簡化圖表，領先導入 ASME B31J（2023 年版）最新規範，針對大徑厚比管件進行精確的應力強度因子（SIF）與撓性係數（Flexibility Factor）之電腦輔助工程（CAE）模擬。在材料冶金維度，則深度剖析 316LN、321 與 347H 等穩定型不銹鋼在海岸環境下的微觀腐蝕機制，重新評估其孔蝕當量（PREN）與應力腐蝕破裂（SCC）抵抗力。最後，在製造工法與實務維度，本研究藉由探討本土指標性廠商「潁璋工程興業有限公司」的實務操作數據，深度解析 3D/5D 冷作彎管（Cold Bending）工法在力學性能優化、徹底消除熱影響區（HAZ）以及突破非破壞檢測（NDT）瓶頸上的具體展現。分析結果證實，透過結合 316LN 高強度不銹鋼材質與冷作彎管工法，並輔以 B31J 規範進行嚴謹的應力校核，將能徹底消除傳統銲接管線的疲勞弱點與腐蝕隱患，為台灣次世代高階發電廠的管線設計提供最具前瞻性與經濟效益的標準指引。 This research report aims to comprehensively and deeply evaluate the stress characteristics of the high-pressure piping in inlet fogging cooling systems and propose feasible engineering optimization solutions. In the dimension of mechanical analysis, this study completely discards the simplified charts of traditional ASME B31.1 and B31.3 Appendix D, pioneering the introduction of the latest ASME B31J (2023 edition) code to conduct precise Computer-Aided Engineering (CAE) simulations of Stress Intensification Factors (SIF) and Flexibility Factors for pipe fittings with large diameter-to-thickness ratios. In the metallurgical dimension, it profoundly analyzes the microscopic corrosion mechanisms of stabilized stainless steels such as 316LN, 321, and 347H in coastal environments, re-evaluating their Pitting Resistance Equivalent Number (PREN) and Stress Corrosion Cracking (SCC) resistance. Finally, in the manufacturing and practical dimension, by examining the practical operational data of a leading local manufacturer, “Ying Zhang Engineering,” this study deeply resolves the specific manifestations of 3D/5D Cold Bending methods in optimizing mechanical performance, completely eliminating the Heat-Affected Zone (HAZ), and breaking through Non-Destructive Testing (NDT) bottlenecks. The analytical results confirm that by combining high-strength 316LN stainless steel with cold bending methods, supplemented by rigorous stress verification using the B31J code, the fatigue weaknesses and corrosion hidden dangers of traditional welded piping can be entirely eliminated. This provides the most forward-looking and economically beneficial standard guidelines for piping design in Taiwan’s next-generation advanced power plants.

一、 前言 / 1. Introduction

在全球極端氣候與淨零碳排（Net Zero）趨勢的雙重驅動下，能源系統正經歷前所未有的結構性變革。台灣電力系統身為一個獨立的海島型電網，在非核家園政策以及大規模太陽光電與離岸風力發電併網的背景下，傳統基載電廠的運轉模式已被徹底顛覆。如今，燃氣複循環發電廠（Combined Cycle Power Plant, CCPP）憑藉著優異的熱效率與極快的升降載率（Ramp rate），已成為填補再生能源發電缺口、維持電網穩定性的絕對核心。 Driven by the dual trends of global extreme climate and Net Zero carbon emissions, energy systems are undergoing unprecedented structural changes. Taiwan’s power grid, as an independent island system, has seen its traditional baseload power plant operational modes completely subverted against the backdrop of a nuclear-free homeland policy and the large-scale grid integration of solar and offshore wind power. Today, Gas-Fired Combined Cycle Power Plants (CCPPs), relying on their excellent thermal efficiency and extremely fast ramp rates, have become the absolute core for filling the renewable energy generation gap and maintaining grid stability.

然而，氣渦輪機（Gas Turbine）本質上屬於恆定體積流量的旋轉機械，其質量流量與環境空氣密度呈高度正相關。當台灣進入酷熱的夏季，環境氣溫時常飆升至 35°C 以上，空氣密度的大幅下降會導致氣渦輪機的壓縮機耗功增加，使得整體出力衰退幅度高達 10% 至 15%。為挽回夏季尖峰時段的發電損失，工程界廣泛採用了進氣霧化冷卻系統。該系統利用操作壓力高達 100 至 200 bar 的高壓泵浦，將去離子超純水加壓後，透過進氣道截面上的微細噴嘴矩陣，噴射出 10 至 50 微米的細小水霧。水霧在進入壓縮機前迅速蒸發並吸收大量顯熱，藉此降低空氣溫度、提升空氣密度，最終使機組出力獲得顯著增益。部分機組甚至會採用超流量噴射（Overspray）技術，讓未蒸發的微小水滴進入壓縮機內部持續冷卻，這不僅進一步提升了發電效率，卻也對系統的穩定供水提出了極端嚴苛的要求。 However, a Gas Turbine is inherently a constant volumetric flow rotating machine, and its mass flow rate is highly positively correlated with ambient air density. When Taiwan enters its scorching summer, ambient temperatures often soar above 35°C. The significant drop in air density leads to increased compressor work consumption, causing overall output to decline by as much as 10% to 15%. To recover power generation losses during the summer peak hours, the engineering sector has widely adopted inlet fogging cooling systems. This system utilizes high-pressure pumps (operating at pressures of 100 to 200 bar) to pressurize deionized ultrapure water, spraying fine water mists of 10 to 50 micrometers through a matrix of micro-nozzles installed on the inlet duct cross-section. The mist rapidly evaporates before entering the compressor, absorbing substantial sensible heat, thereby lowering the air temperature and increasing the air density, ultimately granting a significant boost in unit output. Some units even utilize overspray technology, allowing unevaporated micro-droplets to enter the compressor for continuous cooling; while this further improves generation efficiency, it places extremely stringent demands on the stable water supply of the system.

儘管進氣霧化系統具備無庸置疑的熱力學效益，但負責輸送高壓純水的附屬管線系統，卻在實務運營中暴露出諸多工程隱患。首先，發電廠為了配合電網調度，其負載升降與啟停變得極為頻繁。當系統因應負載變化而快速開關高壓控制閥門時，管線內部的流體動能會發生瞬間轉換，產生劇烈的水錘效應（Water Hammer）。這種高頻率的壓力突波與流體暫態激振力（Fluid Transient Forces），會對管線的轉角、三通與支撐點施加巨大的動態負荷，進而引發高應力低循環疲勞（Low-Cycle Fatigue）破壞。 Despite the undeniable thermodynamic benefits of the inlet fogging system, the auxiliary piping system responsible for transporting high-pressure pure water has exposed numerous engineering hazards during practical operations. First, to accommodate grid dispatching, power plant load ramping and start-stop cycles have become extremely frequent. When the system rapidly opens or closes high-pressure control valves in response to load changes, the fluid kinetic energy inside the pipes undergoes instantaneous conversion, generating severe water hammer effects. These high-frequency pressure surges and fluid transient forces impose immense dynamic loads on pipe bends, tees, and supports, subsequently triggering high-stress low-cycle fatigue failures.

其次，台灣大型電廠如大潭、通霄、興達等，均座落於緊鄰海岸線的地帶，常年暴露於高濕度且富含氯化鈉（NaCl）氣膠的鹽霧環境中。高氯離子環境是沃斯田鐵不銹鋼（Austenitic Stainless Steel）的致命剋星，極易引發局部的孔蝕（Pitting Corrosion）與氯鹽誘發的應力腐蝕破裂（Chloride-Induced Stress Corrosion Cracking, CISCC）。然而，傳統的管線設計往往因循石化廠或高溫蒸汽管線的既有經驗，盲目選用 321 或 347H 等添加鈦（Ti）或鈮（Nb）的穩定型不銹鋼；這些材料在常溫高氯環境下的抗孔蝕能力極為孱弱，根本無法有效抵禦海岸環境的侵蝕。 Secondly, large power plants in Taiwan, such as Datan, Tongxiao, and Hsinta, are all located immediately adjacent to the coastline, chronically exposed to high-humidity salt spray environments rich in sodium chloride (NaCl) aerosols. A high-chloride-ion environment is a deadly nemesis to Austenitic Stainless Steel, highly prone to inducing localized Pitting Corrosion and Chloride-Induced Stress Corrosion Cracking (CISCC). However, traditional piping designs often follow existing experiences from petrochemical plants or high-temperature steam piping, blindly selecting stabilized stainless steels like 321 or 347H, which are alloyed with Titanium (Ti) or Niobium (Nb). The pitting resistance of these materials in ambient-temperature high-chloride environments is extremely weak, rendering them entirely incapable of effectively withstanding coastal environmental erosion.

除了環境與操作條件的挑戰，管線的幾何設計與製造工法也是一大隱憂。過去的工程實踐高度依賴 ASME B31.1（動力管線）或 B31.3（製程管線）標準中的附錄 D（Appendix D）簡化圖表來評估應力強度因子（SIF）。為了改變管線走向，業界普遍大量採購 1.5D 鍛造銲接彎頭（Welded Elbows），並透過手工或半自動對接銲接將其與直管連接。這種做法不僅在管線上留下了無數的熱影響區（Heat-Affected Zone, HAZ）——這些區域往往是殘餘應力集中且耐腐蝕性最差的脆弱節點——更忽視了現代大型複雜管網在真實運作下局部應力放大的真實效應。 Beyond environmental and operational challenges, piping geometric design and manufacturing methods pose another major concern. Past engineering practices heavily relied on the simplified charts in Appendix D of the ASME B31.1 (Power Piping) or B31.3 (Process Piping) standards to evaluate Stress Intensification Factors (SIF). To change piping routing, the industry widely procured large quantities of 1.5D forged Welded Elbows, connecting them to straight pipes via manual or semi-automatic butt welding. This practice not only left countless Heat-Affected Zones (HAZ) across the piping—areas that are often the weakest nodes with residual stress concentration and the poorest corrosion resistance—but also ignored the true effects of localized stress amplification in modern large, complex piping networks under real operating conditions.

為徹底解決上述痛點，本研究決定跳脫傳統設計框架，導入 ASME B31J 現代管線應力評估規範，並結合 CAE 軟體進行深度動態模擬。研究的核心目標包含三部分：一、論證 B31J 規範相較於傳統 B31.1/B31.3 附錄 D 在疲勞評估上的精確性與絕對必要性；二、從物理冶金角度，重新檢視 316LN 與 321、347H 鋼種在特定海岸與高壓交變環境下的真實適用性；三、深入探討冷作彎管（Cold Bending）工法在力學結構上的優越性，並結合台灣本土供應商（如潁璋工程）的實績，量化該工法在免除銲道、降低非破壞檢測（NDT）成本及縮短工期上所帶來的龐大經濟效益。 To thoroughly resolve the aforementioned pain points, this study decided to break out of traditional design frameworks, introducing the ASME B31J modern piping stress evaluation code and integrating CAE software for in-depth dynamic simulations. The core objectives of the research comprise three parts: 1. Demonstrating the accuracy and absolute necessity of the B31J code over the traditional B31.1/B31.3 Appendix D in fatigue evaluation; 2. From a physical metallurgy perspective, re-examining the true applicability of 316LN versus 321 and 347H steel grades in specific coastal and high-pressure alternating environments; 3. Deeply exploring the structural superiority of the Cold Bending method and, integrating the actual performance of local Taiwanese suppliers (such as Ying Zhang Engineering), quantifying the tremendous economic benefits this method brings by eliminating welds, reducing Non-Destructive Testing (NDT) costs, and shortening project schedules.

二、 文獻回顧與理論基礎 / 2. Literature Review and Theoretical Foundation

本章節將針對管線設計中的幾個核心議題進行深度的文獻回顧與理論建構，依序探討應力分析規範的演進、水錘暫態流體力學、不銹鋼物理冶金特性，以及冷作彎管的塑性變形理論。

This section will conduct an in-depth literature review and theoretical construction focusing on several core issues in piping design, sequentially exploring the evolution of stress analysis codes, fluid transient mechanics of water hammer, physical metallurgical characteristics of stainless steel, and the plastic deformation theories of cold bending.

2.1 管線應力分析規範的範式轉移：從 B31 附錄 D 到 B31J / 2.1 Paradigm Shift in Piping Stress Analysis Codes: From B31 Appendix D to B31J

在工業管線設計領域，美國機械工程師學會（ASME）所制定的 B31 系列規範長期以來被奉為全球圭臬。其中，ASME B31.1 專注於發電廠的高可靠度動力管線（Power Piping），而 ASME B31.3 則涵蓋了煉油、石化與多樣化流體製程的管線（Process Piping）。這兩套規範的核心目的，皆在確保管線系統於承受內壓、重力、熱膨脹以及各種偶發負載（如地震、風力、水錘）時，不會發生塑性崩塌、棘輪效應（Ratcheting）或疲勞破壞。 In the field of industrial piping design, the B31 series codes formulated by the American Society of Mechanical Engineers (ASME) have long been regarded as the global gold standard. Among them, ASME B31.1 focuses on high-reliability Power Piping for power plants, while ASME B31.3 covers Process Piping for refineries, petrochemicals, and diverse fluid processes. The core purpose of both sets of codes is to ensure that piping systems will not experience plastic collapse, ratcheting, or fatigue failure when subjected to internal pressure, gravity, thermal expansion, and various occasional loads (such as earthquakes, wind, and water hammer).

進行管線的疲勞與彈性分析時，工程師並非直接計算複雜的三維實體應力，而是採用一維的樑元素（Beam Element）模型。然而，樑模型無法真實反映管件幾何不連續處（如彎頭、三通、大小頭）的局部峰值應力。為此，規範引入了「應力強度因子」（Stress Intensification Factor, SIF 或 i-factor）與「撓性係數」（Flexibility Factor, k-factor）作為修正乘數。SIF 用於放大名義樑應力以預測疲勞壽命；撓性係數則用於修正剛度矩陣，反映彎頭受彎矩時因斷面橢圓化（Ovalization）而產生的額外柔性。 When performing fatigue and elastic analysis on piping, engineers do not directly calculate complex 3D solid stresses; instead, they employ a one-dimensional Beam Element model. However, beam models cannot truly reflect the localized peak stresses at geometric discontinuities of pipe fittings (such as elbows, tees, and reducers). Therefore, the code introduced “Stress Intensification Factors” (SIF or i-factor) and “Flexibility Factors” (k-factor) as modification multipliers. The SIF is used to magnify nominal beam stresses to predict fatigue life; the flexibility factor is used to modify the stiffness matrix, reflecting the additional flexibility caused by cross-sectional ovalization when an elbow is subjected to a bending moment.

數十年來，全球的管線應力軟體（如 CAESAR II, AutoPIPE）皆內建了 ASME B31.3 的附錄 D（Appendix D）或 B31.1 的相應圖表來計算這些因子。附錄 D 的公式極為簡化，主要依賴單一幾何參數——撓性特徵值（Flexibility Characteristic, h）。對於彎頭而言，h 的計算公式為：For decades, global piping stress software (such as CAESAR II, AutoPIPE) built-in the Appendix D of ASME B31.3 or the corresponding charts in B31.1 to calculate these factors. The formulas in Appendix D are highly simplified, primarily relying on a single geometric parameter—the Flexibility Characteristic, h. For elbows, the calculation formula for h is:

h=T⋅R1/r22

其中 T 為公稱壁厚，R1 為彎曲半徑，r2 為管線截面平均半徑。 隨後，撓性係數 k 與平面內外之 SIF (ii,io) 均由 h 直接推導而來：where T is the nominal wall thickness, R1 is the bend radius, and r2 is the mean cross-sectional radius of the pipe. Subsequently, the flexibility factor k and the in-plane/out-of-plane SIFs (ii,io) are directly derived from h:

k=1.65/h

ii = 0.9/h2/3 ; io = 0.75/h2/3

然而，隨著現代製程參數的提升，管線的大徑厚比（D/t ratio）越來越大，幾何形態也日趨複雜。工程界逐漸發現，基於 1940 年代 Markl 實驗數據所建立的附錄 D，在面對現代大管徑薄壁管或特殊三通時存在嚴重的誤差。為了解決此一問題，ASME 歷經長期的研究與大量有限元素法（FEM）虛擬測試，最終推出了 ASME B31J（Standard Method for Test and Calculation of Pipe Stress Factors）標準。 However, as modern process parameters have escalated, the diameter-to-thickness ratio (D/t ratio) of piping has grown larger, and geometric configurations have become increasingly complex. The engineering community gradually discovered that Appendix D, built on Markl’s experimental data from the 1940s, exhibits severe errors when confronted with modern large-diameter thin-walled pipes or special tees. To resolve this issue, ASME, through long-term research and massive Finite Element Method (FEM) virtual testing, finally released the ASME B31J (Standard Method for Test and Calculation of Pipe Stress Factors) code.

自 2020 年版起，ASME B31.3 作出歷史性決策：全面刪除附錄 D，並強制要求（或強烈建議）使用 ASME B31J 進行所有 SIF 與撓性係數的計算。B31J 帶來的變革具有革命性意義：

  1. 多維度矩陣計算 / Multi-dimensional Matrix Calculation：B31J 針對三通（Tees）與交集處提供了高達 12 個獨立的因子，分別對應主管與支管的平面內、平面外與扭轉方向。 / B31J provides up to 12 independent factors for tees and intersections, corresponding respectively to the in-plane, out-of-plane, and torsional directions of the run and branch pipes.
  2. 扭轉 SIF 的引入 / Introduction of Torsional SIF：過去3 預設扭轉 SIF 為 1.0，忽略了扭轉對幾何不連續處的疲勞貢獻，B31J 則填補了此一空白，提供了真實的扭轉強度因子。 / Previously, B31.3 defaulted the torsional SIF to 1.0, ignoring torsion’s fatigue contribution at geometric discontinuities. B31J filled this gap by providing true torsional intensification factors.
  3. 大徑厚比精確化 / Precision in Large D/t Ratios：B31J 涵蓋了D/T ≦ 100 的幾何範圍，消除了舊有經驗公式在極端尺寸下的發散問題。 / B31J covers the geometric range of D/T ≦ 100, eliminating the divergence issues of old empirical formulas at extreme dimensions.

當工程師將舊有的「安全」模型改以 B31J 重新分析時，經常會發現原本合格的管線節點突然超標（出現紅字）。這絕非軟體計算錯誤，而是 B31J 揭露了過去被簡化圖表所掩蓋的真實應力集中風險。 When engineers re-analyze old “safe” models using B31J, they often find that previously qualified piping nodes suddenly exceed limits (showing up as red). This is by no means a software calculation error; rather, it is B31J exposing the true stress concentration risks that were masked by the simplified charts of the past.

2.2 流體暫態與 Markl 疲勞破壞模型 / 2.2 Fluid Transients and Markl Fatigue Failure Model

除了靜態的幾何應力，進氣霧化系統管線的失效機制多半源於流體暫態（Fluid Transients）引發的疲勞。當高壓泵浦瞬間啟動、停止，或快關閥（Quick-Closing Valve）作動時，流體速度的瞬間改變會迫使動能轉化為壓力能，產生沿著管線傳遞的高壓震波，這便是所謂的水錘效應。 Beyond static geometric stresses, the failure mechanisms of inlet fogging piping systems mostly stem from fatigue induced by fluid transients. When high-pressure pumps instantaneously start or stop, or when quick-closing valves actuate, the momentary change in fluid velocity forces kinetic energy to convert into pressure energy, generating high-pressure shockwaves transmitted along the pipeline—this is the so-called water hammer effect.

水錘的理論基礎為 Joukowsky 方程式，其描述了速度變化與壓力上升之間的線性關係：The theoretical foundation of water hammer is the Joukowsky equation, which describes the linear relationship between velocity change and pressure rise:

ΔP=ρ⋅c⋅Δv

式中，ΔP 為壓力增量，ρ 為水體密度，c 為壓力波在彈性管壁內的傳遞聲速（受管材彈性模數與管壁厚度影響），Δv 為流體速度變化量。當這些壓力波傳遞至管線的彎頭或盲端時，會產生沿著管線軸向的巨大不平衡力（Unbalanced Force），迫使管線產生微小幅度的劇烈位移與振動。

where ΔP is the pressure increment, ρ is the fluid density, c is the wave celerity in the elastic pipe wall (affected by the material’s elastic modulus and wall thickness), and Δv is the fluid velocity change. When these pressure waves propagate to elbows or dead ends of the piping, they generate massive Unbalanced Forces along the piping axis, forcing the pipes to undergo violent micro-displacements and vibrations.

管線在吸收熱膨脹位移與抵抗水錘振動時，會在幾何不連續處產生交變應力。ASME 規範評估疲勞壽命的核心是基於 A.R.C. Markl 於 1950 年代執行的旋轉彎曲疲勞試驗。Markl 透過位移控制的全反轉測試，定義了應力強度因子 i 與破壞循環次數 N 的關係：When piping absorbs thermal expansion displacements and resists water hammer vibrations, alternating stresses are generated at geometric discontinuities. The core of ASME code’s fatigue life evaluation is based on the rotary bending fatigue tests conducted by A.R.C. Markl in the 1950s. Through displacement-controlled fully reversed testing, Markl defined the relationship between the stress intensification factor i and cycles to failure N:

i⋅S=245,000⋅N-0.2

其中，S 為名義彎曲應力振幅。Where S is the nominal bending stress amplitude.

在 ASME 疲勞設計框架下，工程師需計算膨脹應力範圍（Expansion Stress Range, SE），並套用應力範圍縮減係數（Stress Range Reduction Factor, f）。f 值與等效循環次數 N 緊密相關：當 N ≦ 7000次時，f=1.0；隨著循環次數增加，f 值逐漸下降，最低可降至 0.3。對於每天因應電網調度而頻繁啟停的進氣霧化系統而言，管線在 20 年的生命週期內輕易會累積超過數萬次的應力交變；因此，極力降低局部 SIF 以確保疲勞壽命大於設計年限，是管線設計的首要任務。 Under the ASME fatigue design framework, engineers must calculate the Expansion Stress Range (SE) and apply the Stress Range Reduction Factor (f). The f value is closely correlated with equivalent cycle times N: when N ≦ 7000 cycles, f=1.0; as cycle counts increase, f gradually decreases, down to a minimum of 0.3. For inlet fogging systems that frequently start and stop daily to accommodate grid dispatch, the piping will easily accumulate tens of thousands of stress alternations over a 20-year lifecycle; therefore, minimizing the local SIF to ensure the fatigue life exceeds the design lifespan is the primary task of piping design.

2.3 海岸環境下的腐蝕機制與合金選擇 (316LN vs. 321/347H) / 2.3 Corrosion Mechanisms and Alloy Selection in Coastal Environments (316LN vs. 321/347H)

解決了力學層面的疲勞問題後，材料的抗腐蝕能力則是決定管線長期妥善率的另一大支柱。台灣的大型發電廠多建於沿海填海造陸地帶，大氣中富含海洋氣膠，氯化鈉沉積率極高。儘管進氣霧化管線內部輸送的是高純水，但管線外部卻長期暴露於惡劣的鹽霧大氣中。在石化與傳統發電領域，工程師常直覺性地選用 321 或 347H 等穩定型不銹鋼作為高級管材。然而，這種選材邏輯在海岸常溫高壓環境中存在嚴重的誤區。 Once the mechanical fatigue issues are resolved, the material’s corrosion resistance becomes the other major pillar determining the long-term availability of the pipeline. Large power plants in Taiwan are mostly built on reclaimed coastal lands, where the atmosphere is rich in marine aerosols and the sodium chloride deposition rate is extremely high. Even though the inlet fogging pipes transport high-purity water internally, the exterior is chronically exposed to harsh salt spray atmospheres. In petrochemical and conventional power sectors, engineers often intuitively select stabilized stainless steels like 321 or 347H as high-grade piping materials. However, this material selection logic is deeply flawed for ambient-temperature, high-pressure coastal environments.

321 不銹鋼透過添加鈦（Ti），347H 透過添加鈮（Nb），其核心目的是為了解決高溫下的「敏化作用」（Sensitization）。當普通奧氏體不銹鋼暴露於 450°C 至 850°C 的高溫環境時，碳原子會與晶界處的鉻結合形成碳化鉻（Cr23C6），導致晶界附近出現「貧鉻區」（Cr-depleted zone），進而引發嚴重的晶界腐蝕。鈦與鈮的碳化物形成能遠大於鉻，因此能優先鎖住碳原子以保全晶界的鉻濃度。但是，進氣霧化系統的操作溫度通常低於 100°C，根本缺乏觸發敏化作用的熱力學條件，這使得穩定型元素的優勢在此毫無發揮餘地。 321 stainless steel is alloyed with Titanium (Ti), and 347H with Niobium (Nb), primarily to address high-temperature “Sensitization”. When standard austenitic stainless steel is exposed to temperatures between 450°C and 850°C, carbon atoms combine with chromium at the grain boundaries to form chromium carbides (Cr23C6), resulting in a “Cr-depleted zone” near the boundaries, which subsequently induces severe intergranular corrosion. The carbide formation energies of titanium and niobium are far greater than that of chromium, so they preferentially lock up the carbon atoms, preserving the chromium concentration at the grain boundaries. However, the operating temperature of inlet fogging systems is typically below 100°C, completely lacking the thermodynamic conditions to trigger sensitization, rendering the advantages of stabilizing elements completely useless here.

在含氯的海岸環境中，管線真正的威脅是孔蝕（Pitting Corrosion）與氯鹽誘發的應力腐蝕破裂（CISCC）。孔蝕的抵抗能力通常透過孔蝕當量（Pitting Resistance Equivalent Number, PREN）來量化，學界公認的經驗公式為：In chloride-containing coastal environments, the real threats to the piping are Pitting Corrosion and Chloride-Induced Stress Corrosion Cracking (CISCC). Pitting resistance is typically quantified using the Pitting Resistance Equivalent Number (PREN), with the widely accepted empirical formula being:

PREN=%Cr+3.3×%Mo+16×%N

公式顯示，鉬（Mo）抵抗孔蝕的能力是鉻的 3.3 倍。由於 321 與 347H 的化學成分中並不含鉬，其 PREN 值通常僅約 18；一旦表面鈍化膜（Passive film）被氯離子局部擊穿，孔蝕便會迅速向管壁深處發展。The formula indicates that Molybdenum (Mo) is 3.3 times more capable of resisting pitting than Chromium. Because the chemical compositions of 321 and 347H do not contain molybdenum, their PREN values are typically around 18; once the surface passive film is locally breached by chloride ions, pitting will rapidly propagate deep into the pipe wall.

相比之下，316LN 不銹鋼（UNS S31653）在冶金設計上展現了極大的針對性優勢。首先，316LN 含有 2.0% 至 3.0% 的鉬，極大地強化了鈍化膜在氯離子環境下的穩定性；其次，透過精確控制的氮（Nitrogen, 0.10% – 0.16%）添加，其 PREN 值可高達 24 至 28，遠勝 321/347H。除了防腐蝕外，氮元素作為強烈的奧氏體穩定劑與間隙固溶強化（Interstitial solid-solution strengthening）元素，能將材料的降伏強度（Yield Strength）從標準 316L 的~170 MPa 大幅提升至 ≧ 275 MPa。更高的降伏強度意味著管線能夠承受更劇烈的水錘壓力波而不發生微觀塑性變形。此外，316LN 較高的層錯能（Stacking Fault Energy）能有效抑制位錯滑移的平面性，顯著降低裂紋尖端的局部應力集中，從而具備卓越的抗應力腐蝕破裂（SCC）能力並降低腐蝕疲勞裂紋成長率（CFCG）。 In contrast, 316LN stainless steel (UNS S31653) exhibits a highly targeted advantage in its metallurgical design. First, 316LN contains 2.0% to 3.0% Molybdenum, which greatly strengthens the stability of the passive film in chloride environments. Second, through precise addition of Nitrogen (0.10% – 0.16%), its PREN can reach as high as 24 to 28, far surpassing 321/347H. Beyond corrosion resistance, Nitrogen acts as a strong austenite stabilizer and interstitial solid-solution strengthening element, significantly increasing the material’s Yield Strength from ~170 MPa for standard 316L up to ≧ 275 MPa. Higher yield strength means the pipe can withstand more violent water hammer pressure waves without micro-plastic deformation. Furthermore, 316LN’s higher Stacking Fault Energy effectively suppresses the planarity of dislocation slip, significantly reducing localized stress concentration at crack tips, thereby endowing it with superior SCC resistance and a lowered Corrosion Fatigue Crack Growth (CFCG) rate.

2.4 冷作彎管的塑性力學特徵 / 2.4 Plastic Mechanics Characteristics of Cold Bending

探討完規範與材料後，製造工法對管線完整性的影響同樣不容忽視。冷作彎管（Cold Bending）技術是指在常溫下，利用旋轉拉彎機（Rotary Draw Bender）配合內部心軸（Mandrel）與外部導模，將直管施加超越降伏點的彎矩，迫使其產生永久塑性變形，形成所需彎曲半徑（如 3D 或 5D）的管件1。相較於傳統 1.5D 鍛造彎頭必須與兩端直管進行對接銲接，冷作彎管能保持管線的一體性，徹底消除熱影響區（HAZ）與銲道帶來的微觀組織缺陷與殘餘應力集中。 Having discussed codes and materials, the impact of manufacturing methods on piping integrity is equally impossible to ignore. Cold Bending technology refers to applying a bending moment exceeding the yield point to a straight pipe at room temperature using a Rotary Draw Bender combined with an internal mandrel and external wiper die, forcing it to undergo permanent plastic deformation to form a fitting with a desired bend radius (e.g., 3D or 5D)1. Compared to traditional 1.5D forged elbows, which must be butt-welded to straight pipes at both ends, cold bending maintains the integrality of the pipeline, completely eliminating the Heat-Affected Zones (HAZ) and the microstructural defects and residual stress concentrations brought by weld seams.

然而，冷彎過程本質上是大變形塑性力學過程，伴隨著三大物理現象，必須在設計階段嚴格控制： However, the cold bending process is inherently a large-deformation plastic mechanics process accompanied by three major physical phenomena that must be strictly controlled during the design phase:

  1. 管壁減薄（Wall Thinning）：在彎曲力矩作用下，管線外側纖維承受拉應力導致管壁變薄，內側則因承受壓應力而變厚。工程界與 ASME 規範普遍接受的經驗預測公式為 tthinning=50/(n+1)%，其中 n 為彎曲半徑與管外徑的比值（n=R1/D）。以 5D 彎管為例，最大減薄率理論值約為33%。設計工程師必須選用足夠初始壁厚（如 Schedule 80 或 XXS）的母管，確保減薄後的最薄點仍大於 B31.3 規定的壓力設計最小厚度（tm=(P⋅D)/2(S⋅E+P⋅Y)）。Wall Thinning: Under the action of the bending moment, the outer fibers of the pipe endure tensile stress, causing the wall to thin, while the inner side thickens due to compressive stress. The empirical prediction formula widely accepted by the engineering community and ASME codes is tthinning=50/(n+1)%, where n is the ratio of the bend radius to the outer diameter (n=R1/D). For a 5D bend, the theoretical maximum thinning rate is approximately 8.33%. Design engineers must select parent pipes with sufficient initial wall thickness (such as Schedule 80 or XXS) to ensure that the thinnest point after thinning remains greater than the minimum pressure design thickness (tm=(P⋅D)/2(S⋅E+P⋅Y)) stipulated by B31.3.
  2. 截面橢圓化（Ovalization/Von Karman Effect）：在彎曲過程中，管線截面會因徑向分力而趨向扁平，形成橢圓狀。橢圓度的計算式為Oovalization =(Dmax-Dmin)/Dnom ×100%。嚴重的橢圓化不僅會增加流體阻力，更會大幅改變該斷面的慣性矩，進而影響整體管線的剛度。國際管線專案規範（如 DNV 或特定 EPC 標準）通常要求冷彎管的最終橢圓化率不得超過5%。透過高精度的數控彎管機與精密心軸的支撐，現代冷彎工法已能將橢圓化嚴格控制在此極限值之內1。 Ovalization (Von Karman Effect): During bending, the pipe cross-section tends to flatten due to radial force components, forming an oval shape. The ovality calculation formula is Oovalization =(Dmax-Dmin)/Dnom ×100%. Severe ovalization not only increases fluid resistance but also drastically alters the section’s moment of inertia, subsequently affecting overall pipe stiffness. International piping project specifications (such as DNV or specific EPC standards) usually require the final ovality of cold bends not to exceed 2.5%. Supported by high-precision CNC bending machines and precision mandrels, modern cold bending methods can strictly control ovalization within this limit1.
  3. 彈性回彈與應變硬化（Springback & Strain Hardening）：冷彎完成卸載後，彈性應變的釋放會導致管線彎曲角度稍微回彈。冷彎的彈性回彈係數通常介於05 至 1.15 之間，這意味著彎管機必須超彎（Overbend） 5% 至 15% 才能達到目標角度。同時，由於 316LN 材料本身具備較強的應變硬化特性（硬化指數n≈0.1∼0.3），冷彎區域的降伏強度會進一步提升，使其在後續承受內壓與水錘衝擊時具備更高的結構裕度。Springback & Strain Hardening: After unloading from cold bending, the release of elastic strain causes the pipe’s bend angle to spring back slightly. The springback coefficient for cold bending usually ranges between 1.05 and 1.15, meaning the bending machine must overbend by 5% to 15% to achieve the target angle. Simultaneously, because the 316LN material inherently possesses strong strain-hardening characteristics (hardening exponent n≈0.1∼0.3), the yield strength of the cold-bent region will be further elevated, endowing it with a higher structural margin when subsequently subjected to internal pressure and water hammer impacts.

三、 研究方法與分析模型建立 / 3. Research Methodology and Analysis Model Establishment

為了具體量化評估傳統銲接彎頭與冷作彎管在進氣霧化系統中的力學與經濟差異，本研究建構了一套整合 CAE 應力分析、疲勞映射與工程經濟效益量化的綜合評估架構。以下詳細說明分析模型的設定與評估步驟。

To concretely quantify and evaluate the mechanical and economic differences between traditional welded elbows and cold bends in inlet fogging systems, this study constructed a comprehensive evaluation framework integrating CAE stress analysis, fatigue mapping, and engineering economic benefit quantification. The following details the setup and evaluation steps of the analysis models.

3.1 ASME B31J 應力交變與暫態模擬設定 / 3.1 ASME B31J Alternating Stress and Transient Simulation Setup

本研究選定台灣某大型複循環發電廠（以大潭或通霄電廠之機組為藍本）的進氣霧化系統高壓主水管線作為分析標的。管線基礎參數設定為：管徑 NPS 4（外徑 114.3 mm），採用 Schedule 80（壁厚 8.56 mm）的規格；管線材質選定具備高強度與高抗孔蝕能力的 316LN 不銹鋼（ASTM A312 UNS S31653）；系統的設計壓力與溫度分別設定為 150 bar（約 2,175 psi）與 45°C。 This study selected the high-pressure main water piping of the inlet fogging system of a large combined cycle power plant in Taiwan (modeled after units at the Datan or Tongxiao power plants) as the analysis target. The basic piping parameters are set as: pipe size NPS 4 (outer diameter 114.3 mm), using Schedule 80 (wall thickness 8.56 mm); the pipe material is selected as 316LN stainless steel (ASTM A312 UNS S31653), possessing high strength and high pitting resistance; the design pressure and temperature of the system are set at 150 bar (approx. 2,175 psi) and 45°C, respectively.

在模擬環境方面，本研究使用 Bentley AutoPIPE 或 Hexagon CAESAR II 進行三維管線佈置建模。有別於傳統做法，本模型的關鍵設定在於摒棄軟體預設的 B31.3 附錄 D，強制勾選並套用「ASME B31J-2023」規範，以啟動大徑厚比及精確 SIF/撓性係數的高階演算法。為了進行對照，模型分為兩組：

  • Case A（傳統設計 / Traditional Design）：管線走向改變處全面採用標準5D 鍛造銲接彎頭（Welded Elbows），模型中詳細包含彎頭與直管連接處的環向對接銲道（Butt welds）。 / At locations where the pipeline changes direction, standard 1.5D forged Welded Elbows are comprehensively used. The model details the circumferential butt welds connecting the elbows to the straight pipes.
  • Case B（優化工法 / Optimized Method）：管線走向改變處全面採用 5D 彎曲半徑之冷作彎管（Cold Bending），該區域設定為一體成型，無任何中介銲道。 / At directional changes, 5D bend radius Cold Bends are comprehensively used. This area is set as integrally formed without any intermediate welds. In terms of simulation environment, this study utilizes Bentley AutoPIPE or Hexagon CAESAR II for 3D piping layout modeling. Distinct from traditional practices, the key setup of this model lies in discarding the software’s default B31.3 Appendix D, mandatorily checking and applying the “ASME B31J-2023” code to trigger advanced algorithms for large D/t ratios and precise SIF/flexibility factors. For comparison, the model is divided into two groups:

在負載譜（Load Cases）的建立上，除了考量包含管線自重、流體重量、保溫層重量與內壓的靜態負載（Sustained），以及模擬環境低溫至運轉溫度變化的熱膨脹負載（Expansion）外；更關鍵的是加入了暫態偶發負載（Occasional/Water Hammer）。透過基於 Joukowsky 方程式模擬進氣霧化快關閥於 0.5 秒內閉合所產生的壓力突波，計算所得之不平衡暫態力將以動態時間歷程分析（Time History Analysis）施加於系統盲端與彎管轉向處，以真實反映運作實況。 In establishing the Load Cases, aside from considering Sustained loads including pipe self-weight, fluid weight, insulation weight, and internal pressure, as well as Expansion loads simulating the change from ambient low temperature to operating temperature; crucially, Occasional/Water Hammer transient loads were added. By simulating the pressure surge generated by the inlet fogging quick-closing valve shutting within 0.5 seconds based on the Joukowsky equation, the calculated unbalanced transient forces are applied via Time History Analysis to system dead ends and bend turns, truly reflecting real operational scenarios.

3.2 疲勞壽命演算法 / 3.2 Fatigue Life Algorithm

取得模擬數據後，研究將提取 Case A 與 Case B 在系統最高應力節點（通常為第一或第二個彎折處）的應力強度因子（包含面內 ii、面外 io）與彎矩（Mi,Mo）。依據 ASME 規範，首先計算合成膨脹應力範圍 SE：After obtaining the simulation data, the study extracts the Stress Intensification Factors (including in-plane ii, out-of-plane io) and bending moments (Mi,Mo) at the system’s highest stress nodes (usually the first or second bends) for Case A and Case B. According to ASME codes, the combined Expansion Stress Range SE is first calculated:

SE=√((iiMi )2+(ioMo )2 )/Z

接著，將此交變應力代入 Markl 疲勞經驗公式 N=(245,000/SE )5，並輔以 Miner 累積破壞法則（Cumulative Damage Rule, ∑ni/Ni ≦ 1.0 ）。透過此映射過程，便能精確評估在系統設計壽命內，水錘與熱交變疊加作用下，兩種工法的管線是否會發生低循環疲勞破裂。 Next, this alternating stress is substituted into the Markl empirical fatigue formula N=(245,000/SE )5, supplemented by the Miner Cumulative Damage Rule (∑ni/Ni ≦ 1.0). Through this mapping process, it becomes possible to accurately evaluate whether the piping of the two methods will suffer low-cycle fatigue failure under the superimposed effects of water hammer and thermal alternation over the system’s design life.

3.3 經濟效益與排程量化模型 / 3.3 Economic Benefit and Scheduling Quantification Model

工程的最佳化不能僅限於力學數據的提升，更必須具備實務上的經濟可行性。因此，本研究引入了專案管理視角，透過檢索並彙整台灣本土指標性管線承攬商「潁璋工程興業有限公司」在森霸電廠、興達電廠以及離岸風力發電等專案中的實際施工數據與專利工法資料，建立了一套經濟與排程量化模型2。 Engineering optimization cannot be limited merely to the enhancement of mechanical data; it must also possess practical economic feasibility. Therefore, this study introduced a project management perspective, establishing a quantified economic and scheduling model by retrieving and collating actual construction data and patented method information from a leading local Taiwanese piping contractor, “Ying Zhang Engineering,” in projects such as Sunba Power Plant, Hsinta Power Plant, and offshore wind power2.

此模型涵蓋三大評估構面：This model covers three major evaluation dimensions:

  • 直接物料與倉儲成本的差異，量化省去採購5D 不銹鋼鍛造彎頭及昂貴氬銲（GTAW）銲材的效益，並對比增加的直線管材與彎管機具攤提成本4；First, differences in direct material and warehousing costs, quantifying the benefits of eliminating the procurement of 1.5D forged stainless steel elbows and expensive Gas Tungsten Arc Welding (GTAW) consumables, contrasted with the added straight pipe materials and bending machine amortization costs4;
  • 直接人工與排程縮減，對比傳統繁瑣工序（裁切、開坡口、假銲、打底、蓋面）與冷作彎管自動化工法（參數設定、CNC 拉彎、橢圓度檢驗）在單一節點上的工時差異1；Second, direct labor and schedule reduction, comparing the labor-hour differences at a single node between tedious traditional procedures (cutting, beveling, tack welding, root pass, capping) and the cold bending automated method (parameter setting, CNC draw-bending, ovality inspection)1;
  • 品質檢驗（NDT）隱性成本，依據高壓管線規範，評估因消除對接銲道而省下的射線（RT）或超音波（UT）檢測費用，以及歸零的剷修（Repair）時間與衍生風險成本2。Third, hidden Non-Destructive Testing (NDT) costs, assessing the saved Radiographic Testing (RT) or Ultrasonic Testing (UT) fees due to the elimination of butt welds per high-pressure piping codes, as well as the eliminated repair times and derivative risk costs2.

四、 結果與討論 / 4. Results and Discussion

本章節將整合前述的方法論與模擬結果，從應力規範的轉變、力學決策、材料抗性，一路推進至實務施工層面的綜合效益探討。

This chapter will integrate the aforementioned methodologies and simulation results, propelling from the shift in stress codes, mechanical decisions, and material resistance, all the way to a comprehensive benefit discussion at the practical construction level.

4.1 ASME B31J 規範下 SIF 與撓性係數之巨變解析 / 4.1 Resolution of Massive Changes in SIF and Flexibility Factors under the ASME B31J Code

當模型強制啟用 ASME B31J 規範重新校核後，管線元件的幾何應力評估發生了根本性的轉移。表1  呈現了 NPS 4 (Sch 80) 管線在使用不同設計規範與元件類型下的關鍵參數對比。 Once the model forces the use of the ASME B31J code for re-verification, the geometric stress evaluation of piping components undergoes a fundamental shift. Table 1 presents a comparison of key parameters for NPS 4 (Sch 80) piping using different design codes and component types.

幾何元件與分析規範 / Element & Code B31.3 App. D 估算 SIF / Est. SIF B31J (2023) 精算 SIF (面內 ii​) / Calc. SIF (In-plane ii​) 撓性係數 (k) 比較 / Flex. Factor (k) 應力集中根源探討 / Source of Stress Concentration
Case A: 1.5D 銲接彎頭 (含環向對接銲道) / 1.5D Welded Elbow (with circumferential butt weld) ~1.65 2.45 – 2.80 附錄D: 4.2 / B31J: 4.0 / App.D: 4.2 / B31J: 4.0 彎管曲率過急疊加銲道根部之微觀缺口效應（Notch effect） / Sharp curvature combined with micro-notch effect at weld root
Case B: 3D 冷作彎管 (無中介銲道) / 3D Cold Bend (no intermediate weld) N/A 1.15 附錄D: N/A / B31J: 2.1 / App.D: N/A / B31J: 2.1 曲率較緩，減輕斷面橢圓化引發之二次應力 / Gentler curvature mitigates secondary stress induced by cross-sectional ovalization
Case B: 5D 冷作彎管 (無中介銲道) / 5D Cold Bend (no intermediate weld) N/A 1.00 (理論極限值) / 1.00 (Theoretical limit) 附錄D: N/A / B31J: 1.3 / App.D: N/A / B31J: 1.3 大半徑且表面平滑，力學行為趨近直管樑理論 / Large radius with smooth surface; mechanical behavior approaches straight pipe beam theory

表 1：不同規範與管件類型之應力強度因子與撓性係數比較 / Table 1: Comparison of Stress Intensification Factors and Flexibility Factors across different codes and fitting types

由表 1 的數據可以明確觀察到，若工程師固守舊版 B31.3 附錄 D 的簡化公式，將嚴重低估 1.5D 銲接彎頭在承受彎矩時的應力集中風險，誤差幅度往往高達 50% 以上。當模型轉換至 B31J 後，由於新規範利用 FEM 精確捕捉了彎頭內側曲率與相鄰直管銲接處的複合應力梯度，1.5D 彎頭的 SIF 瞬間飆升至 2.45 以上。這正是許多在舊版軟體中呈現合格的系統，在更新至 B31J 後紛紛出現應力超標的主因。 From the data in Table 3, it is distinctly observable that if engineers stick to the simplified formulas of the old B31.3 Appendix D, they will severely underestimate the stress concentration risks of 1.5D welded elbows when subjected to bending moments, with error margins often exceeding 50%. When the model transitions to B31J, because the new code utilizes FEM to accurately capture the compound stress gradients between the elbow’s inner curvature and the adjacent straight pipe weld, the SIF of the 1.5D elbow instantly shoots up past 2.45. This is the exact reason why many systems that appeared qualified in old software abruptly show stress exceedances upon updating to B31J.

相反地，Case B 所採用的 5D 冷作彎管則展現出極致的力學優勢。受惠於極大的彎曲半徑（R1=5D），其撓性特徵值 h 顯著增大，這意味著彎管在受彎矩時的斷面橢圓化程度大幅減輕，不易在管壁側面產生高幅度的貫穿厚度彎曲應力。更為關鍵的是，5D 冷彎段是一體成型且不存在對接銲縫。B31J 規範明確指出，在無銲接缺口干擾的情況下，這類大半徑彎管的 SIF 可降至理論極限值 1.0。儘管其較低的撓性係數（k≈1.3）表示管件較為剛直，但由於 SIF 大幅縮減，整體的應力計算值 SE 反而遠低於傳統設計。這項力學上的根本差異，直接影響了後續營運方針對管線幾何配置的決策方向。 Conversely, the 5D cold bend adopted in Case B exhibits extreme mechanical advantages. Benefiting from an immensely large bend radius (R1=5D), its flexibility characteristic h significantly increases, meaning that the degree of cross-sectional ovalization when subjected to bending moments is vastly reduced, making it less prone to generating high-amplitude through-wall bending stresses on the pipe flanks. More crucially, the 5D cold-bent section is integrally formed and devoid of butt welds. The B31J code explicitly states that without weld notch interference, the SIF of such large-radius bends can drop to the theoretical limit of 1.0. Although its lower flexibility factor (k≈1.3) indicates that the fitting is more rigid, the drastic reduction in SIF causes the overall calculated stress SE to fall far below traditional designs. This fundamental mechanical difference directly influenced subsequent decisions by operators regarding piping geometric configurations.

4.2 營運方在管線上選擇 3D/5D 彎徑之決策考量 / 4.2 Operator Decision Considerations for Selecting 3D/5D Bend Radii

基於上述的應力模擬結果，營運方（如台電或民營電廠）在規劃高壓進氣霧化冷卻系統時，已開始逐步捨棄採購傳統的 1.5D 彎頭，轉而在系統規範中強制要求採用 3D 或 5D 的大彎曲半徑（Bend Radius）冷作彎管。這項工程決策不僅考量了靜態應力，更是基於流體動力學與管線疲勞極限的雙重綜合考量： Based on the aforementioned stress simulation results, operators (such as Taipower or independent power producers), when planning high-pressure inlet fogging cooling systems, have begun to progressively abandon the procurement of traditional 1.5D elbows. Instead, they mandate the use of large bend radius (3D or 5D) cold bends in system specifications. This engineering decision not only accounts for static stresses but is built upon a dual comprehensive consideration of fluid dynamics and piping fatigue limits:

  1. 流體平順度與壓降優化 / Fluid Smoothness and Pressure Drop Optimization：在流體特性上，3D/5D 彎管具有平滑且較長的過渡曲率。這能大幅降低高壓水柱在轉向時的壓力降與內部紊流擾動，不僅減輕了流體對管壁的沖刷耗損，更能從源頭降低因水錘效應引發的暫態激振力4。 In terms of fluid characteristics, 3D/5D bends feature smooth and longer transitional curvatures. This drastically reduces the pressure drop and internal turbulent disturbances of high-pressure water columns during directional changes, which not only mitigates erosive wear of the fluid against the pipe wall but also fundamentally lowers the transient excitation forces induced by water hammer effects4.
  2. 應力強度因子（SIF）的斷崖式下降 / Cliff-like Drop in Stress Intensification Factor (SIF)：面對發電廠頻繁啟停所帶來的交變應力，營運方必須尋求能最有效緩解應力集中的幾何型態。正如 B31J 的評估結果所示，5D 冷彎能將 SIF 從5D 彎頭的 2.80 直接壓低至 1.00，這賦予了管線絕佳的抗疲勞裕度。 Facing alternating stresses brought by frequent start-stops in power plants, operators must seek geometric configurations that most effectively alleviate stress concentrations. As shown in the B31J evaluation results, a 5D cold bend can directly compress the SIF from 2.80 (for a 1.5D elbow) down to 1.00, endowing the piping with exceptional fatigue resistance margins.
  3. 管壁減薄率（Wall Thinning）的物理妥協 / Physical Compromise on Wall Thinning：儘管冷彎工法具備力學優勢，營運方仍必須面對大變形加工帶來的物理限制。依據規範的減薄預測公式tthinning=50/(n+1)%，若選擇 3D 彎管（n=3），最大理論減薄率為5%；若選擇 5D 彎管（n=5），減薄率則微幅降至約 8.33%。為了在減薄後仍能滿足壓力設計最小厚度 tm，營運方通常會從源頭配套採購 Schedule 80 或 XXS 等級的厚壁母管。 Despite the mechanical advantages of cold bending, operators must confront the physical limitations brought by large-deformation processing. According to the code’s thinning prediction formula tthinning=50/(n+1)%, if a 3D bend (n=3) is chosen, the maximum theoretical thinning rate is 12.5%; for a 5D bend (n=5), the thinning rate drops slightly to around 8.33%. To ensure the thinned section still meets the minimum pressure design thickness tm, operators typically procure thicker parent pipes, such as Schedule 80 or XXS grades, at the source.
  4. 橢圓化（Ovalization）控制 / Ovalization Control：管線截面在冷彎過程中的橢圓化若不受控，將導致剛度改變與二次應力飆升。因此，營運方的規範文件（如 DNV 或中鼎 EPC 標準）必然嚴格要求成型後的橢圓度必須小於5%。5D 彎徑相較於更急促的彎度，能透過較和緩的受力分佈，更自然且穩定地將橢圓化現象控制在安全極限值內。 If the pipe cross-section ovalization during cold bending is uncontrolled, it will cause altered stiffness and surging secondary stresses. Thus, operator specification documents (like DNV or CTCI EPC standards) mandatorily enforce that post-forming ovality must be less than 2.5%. Compared to sharper bends, a 5D radius allows for a gentler force distribution, controlling ovalization more naturally and stably within safe limits.

綜合上述因素，5D 彎管雖然在現場佈置時需要較大的轉向空間，但因其力學表現最為堅韌，往往成為高壓主幹管的首選；而 3D 彎管則在空間較為侷限的氣渦輪機進氣道周邊次系統中，提供了一個完美的折衷方案。 Synthesizing the above factors, while a 5D bend requires larger routing space on site, its supremely resilient mechanical performance often makes it the first choice for high-pressure main trunks. Meanwhile, 3D bends provide a perfect compromise for secondary subsystems surrounding the gas turbine inlet duct where space is more constrained.

4.3 水錘暫態交變應力與疲勞壽命延展（Markl 曲線映射） / 4.3 Water Hammer Transient Alternating Stress and Fatigue Life Extension (Markl Curve Mapping)

了解了幾何彎徑的決策依據後，我們進一步將這些參數代入動態的疲勞模型中。在水錘時程分析中，當進氣霧化泵停止或閥門快關時，Joukowsky 壓力波會在極短時間內（∼0.1s）對管線轉角處施加強大的不平衡暫態推力。 Having understood the decision basis for geometric bend radii, we further substitute these parameters into the dynamic fatigue model. In the water hammer time history analysis, when the inlet fogging pump stops or the valve quickly closes, the Joukowsky pressure wave exerts massive unbalanced transient thrusts on the piping corners within an extremely short time (∼0.1s).

在 Case A（1.5D 銲接彎頭）的模型中，這股巨大推力產生的彎矩在經過SIF≈2.8 的放大後，導致節點的峰值交變應力（Salt）常常逼近甚至突破 B31.3 中針對偶發負載（Occasional Load）的許用應力極限。若將這些高達數百 MPa 的交變應力代入 Markl 疲勞公式 N=(245,000/(i⋅S))5 中，結果令人堪憂。傳統銲接彎頭不僅 i 值高，且銲縫根部天然存在的幾何不連續與潛在的微觀夾渣（Slag inclusion），更是絕佳的疲勞裂紋萌生點。在每天多次負載調度的頻繁衝擊下，Case A 的安全循環壽命（N）計算值可能迅速跌破 20,000 次，這意味著在機組運轉的短短幾年內，銲道周邊極可能爆發疲勞滲漏甚至斷裂失效。 In the Case A (1.5D Welded Elbow) model, the bending moment generated by this immense thrust, magnified by an SIF≈2.8, causes the peak alternating stress (Salt) at the nodes to often approach or even breach the allowable stress limit for Occasional Loads under B31.3. If these alternating stresses, reaching hundreds of MPa, are substituted into the Markl fatigue formula  N=(245,000/(i⋅S))5, the results are alarming. Traditional welded elbows not only have high i values, but the inherent geometric discontinuity and potential micro-slag inclusions at the weld root serve as excellent initiation sites for fatigue cracks. Under frequent impacts from multiple daily load dispatches, the calculated safe cycle life (N) for Case A could rapidly plunge below 20,000 cycles. This implies that within just a few years of unit operation, the area around the welds is highly likely to erupt in fatigue leaks or even rupture failures.

反觀 Case B（5D 冷作彎管），由於其i≈1.0，有效交變應力被大幅壓縮至原先的三分之一左右。即便考量到冷彎成型過程中所造成的應變硬化與少許殘餘應力，其落在 Markl 曲線上的理論疲勞壽命也能輕鬆突破 100,000 次，順利跨入高循環疲勞（High-Cycle Fatigue）的安全區域。冷作彎管徹底排除了幾何尖銳角與冶金變異區，使管線在面臨流體激振時展現出無與倫比的強韌性。 In stark contrast, for Case B (5D Cold Bend), owing to its i≈1.0, the effective alternating stress is drastically compressed to about one-third of the original. Even factoring in strain hardening and minor residual stresses resulting from the cold forming process, its theoretical fatigue life mapped onto the Markl curve easily surpasses 100,000 cycles, smoothly crossing into the safe zone of High-Cycle Fatigue. Cold bending completely eliminates sharp geometric angles and metallurgical variation zones, allowing the pipeline to exhibit unparalleled toughness when faced with fluid excitation.

4.4 台灣海岸環境之材料冶金分析（316LN 壓倒性優勢） / 4.4 Material Metallurgical Analysis in Taiwan’s Coastal Environment (Overwhelming Advantage of 316LN)

雖然透過冷彎優化幾何能大幅提升抗疲勞能力，但在台灣嚴苛的海岸鹽霧環境中，單靠幾何設計並不足以確保管線的長治久安，材料本身的冶金抗性更是不可或缺的防線。表2統整了業界常見之高級奧氏體不銹鋼的化學組成與冶金性能指標。 Although optimizing geometry via cold bending can vastly improve fatigue resistance, in Taiwan’s severe coastal salt-spray environment, geometric design alone is insufficient to ensure the pipeline’s long-term stability; the material’s inherent metallurgical resistance forms an indispensable defense line. Table 2 collates the chemical compositions and metallurgical performance indicators of high-grade austenitic stainless steels commonly seen in the industry.

鋼種 (UNS) / Steel Grade (UNS) 關鍵合金元素特徵 / Key Alloy Features PREN 孔蝕當量 / PREN 常溫抗孔蝕能力 / Ambient Pitting Resistance 降伏強度 (MPa) / Yield Strength 海岸氯鹽環境 SCC 抵抗力 / SCC Resistance in Coastal Chloride Env.
347H (S34709) 高碳，添加鈮 (Nb) / High Carbon, added Niobium (Nb) ~18 – 19 弱 / Weak ~205 差，極易沿蝕孔萌生 SCC 裂紋 / Poor, SCC cracks easily initiate along pits
321 (S32100) 中碳，添加鈦 (Ti) / Mid Carbon, added Titanium (Ti) ~18 – 19 弱 / Weak ~205 差，極易沿蝕孔萌生 SCC 裂紋 / Poor, SCC cracks easily initiate along pits
316LN (S31653)

 

 超低碳，2-3% Mo，0.1-0.16% N / Ultra-low Carbon, 2-3% Mo, 0.1-0.16% N ~24 – 28 優異 / Excellent ≧275 極佳，高層錯能抑制裂紋成長 / Excellent, high stacking fault energy suppresses crack growth

表 2：進氣霧化系統高壓管線備選不銹鋼之冶金特徵比較 / Table 2: Comparison of Metallurgical Features of Candidate Stainless Steels for High-Pressure Piping in Inlet Fogging Systems

深入探究物理冶金學機制可知，321 與 347H 的設計初衷其實是為了解決「高溫晶界敏化」。這些鋼種中的鈦與鈮能在高溫區間優先形成碳化物，避免鉻元素被消耗以防止晶界腐蝕。然而，進氣霧化系統輸送的卻是低溫冷水，根本不存在觸發敏化作用的熱力學條件。相反地，海岸電廠大氣中高濃度的氯離子會無情地破壞不銹鋼表面的富鉻鈍化膜。在缺乏鉬（Mo）元素保護的情況下，321 與 347H 的鈍化膜一旦被擊穿，就會形成深邃的孔蝕，並在水錘交變應力的催化下，迅速轉化為應力腐蝕破裂（SCC）或腐蝕疲勞裂紋，最終導致管線爆裂。 Delving deep into physical metallurgy mechanisms reveals that the original design intent of 321 and 347H was actually to solve “high-temperature intergranular sensitization”. The titanium and niobium in these steel grades can preferentially form carbides in high-temperature ranges, preventing chromium depletion to avert intergranular corrosion. However, inlet fogging systems transport low-temperature cold water; the thermodynamic conditions to trigger sensitization simply do not exist. Conversely, the high concentration of chloride ions in the coastal power plant atmosphere relentlessly attacks the chromium-rich passive film on the stainless steel surface. Lacking the protection of Molybdenum (Mo), once the passive films of 321 and 347H are breached, deep pitting occurs. Catalyzed by alternating water hammer stresses, this rapidly transitions into Stress Corrosion Cracking (SCC) or corrosion fatigue cracks, ultimately leading to pipe bursts.

在此背景下，316LN 不銹鋼展現了極具針對性的壓倒性優勢。其所含的 2-3% 鉬，極大地強化了抵抗氯離子破壞鈍化膜的能力，使得 PREN 值躍升至 24 以上，將孔蝕萌生機率降至極低。更為精妙的是氮（N）的加入；氮不僅進一步推升了 PREN 值，還以間隙原子的形式固溶於奧氏體晶格中，對位錯滑移產生強大的阻力，直接將材料的降伏強度提升了 30% 以上（達到 ≧275 MPa）。這項強度的提升，使得管線在承受水錘衝擊時不易發生微觀塑性變形。此外，316LN 的高層錯能（Stacking Fault Energy）促使位錯傾向以交滑移而非平面滑移運動，大幅削弱了局部應力集中，賦予材料優異的抗 SCC 能力與極低的腐蝕疲勞裂紋成長率。因此，將 316LN 用作進氣霧化系統的管材，無疑是兼顧力學強度與海岸環境抗性的唯一正解。 Against this backdrop, 316LN stainless steel demonstrates a highly targeted and overwhelming advantage. The 2-3% molybdenum it contains vastly bolsters the capacity to resist chloride ion damage to the passive film, shooting its PREN value above 24 and reducing pitting initiation probabilities to an absolute minimum. Even more ingenious is the addition of Nitrogen (N); nitrogen not only further pushes up the PREN value but also dissolves as interstitial atoms within the austenite lattice, posing strong resistance to dislocation slip. This directly boosts the material’s yield strength by over 30% (reaching ≧275 MPa). This strength enhancement makes the pipeline far less likely to undergo micro-plastic deformation under water hammer impacts. Additionally, 316LN’s high Stacking Fault Energy induces dislocations to move via cross-slip rather than planar slip, substantially dampening localized stress concentrations and granting the material outstanding SCC resistance alongside exceedingly low corrosion fatigue crack growth rates. Therefore, utilizing 316LN as the piping material for inlet fogging systems is indisputably the single correct solution balancing mechanical strength and coastal environmental resistance.

4.5 潁璋工程冷作彎管工法實務操作下之綜合效益 / 4.5 Comprehensive Benefits Under Practical Operations of Ying Zhang Engineering’s Cold Bending Method

將正確的規範、優化的幾何以及適當的材料結合後，最終的成功仍有賴於實務工程的落實。若僅在力學軟體中論證，冷作彎管的優勢可能僅流於學術探討；但在實際工程推動上，該技術已在台灣本土展現出翻轉產業成本結構的強大潛力。透過檢視國內管線製造先驅「潁璋工程興業有限公司」的實務操作數據，我們發現其在高雄的工廠內已整備了半自動化及 CNC 數控管類製造流程，具備 0.5 吋至 8 吋管線的高階冷作彎管能力2。其冷彎技術不僅成功應用於森霸電廠、興達電廠與台中電廠的燃氣複循環管線，更推廣至離岸風電與海軍艦艇等嚴苛專案中2。 After combining correct codes, optimized geometries, and appropriate materials, ultimate success still depends on practical engineering execution. If proven only within mechanical software, the advantages of cold bending might remain mere academic discourse; yet, in actual engineering rollout, this technology has already demonstrated a powerful potential in Taiwan to overturn industry cost structures. By examining the practical operational data of domestic pipe-manufacturing pioneer “Ying Zhang Engineering,” we found that they have equipped their Kaohsiung factory with semi-automated and CNC pipe manufacturing processes, possessing high-end cold bending capabilities for 0.5″ to 8″ piping2. Their cold bending technology has not only been successfully applied to the CCPP piping of Sunba, Hsinta, and Taichung power plants but has also expanded into rigorous projects like offshore wind power and naval vessels2.

在實務操作下，冷作彎管工法不僅體現了力學上的進步，更帶來了以下四個維度的顯著專案效益，如表 5 所彙整： Under practical operations, the cold bending method not only embodies mechanical advancement but also brings significant project benefits across the following four dimensions, as summarized in Table 5:

  1. 消滅 NDT 檢測瓶頸與隱性風險 / Eliminating NDT Bottlenecks and Hidden Risks：傳統高壓管線的對接銲道高度依賴 100% 射線檢測（RT）或超音波檢測（UT）來把關安全。冷作工法透過一體成型的無銲道設計，不僅徹底歸零了 NDT 的高昂費用，更排除了因銲道不合格需耗時剷修（Repair）並重新檢驗的巨大風險，大幅提升了建廠專案的如期完工率2。 Traditional high-pressure piping butt welds rely heavily on 100% Radiographic Testing (RT) or Ultrasonic Testing (UT) for safety assurance. The cold bending method, via its integrally formed weld-free design, not only zeros out exorbitant NDT costs but entirely removes the immense risks of time-consuming repairs and re-inspections due to failed welds, tremendously boosting plant construction on-time completion rates2.
  2. 精準克服彈性回彈（Springback） / Accurately Overcoming Springback：高強度金屬如 316LN，在冷彎卸載後必然會產生一定程度的角度回彈。在潁璋工程的實務操作中，透過 CNC 設備設定，能精確計算出05 至 1.15 的彈性回彈係數，並以 5% 至 15% 的超彎（Overbend）進行事前補償，確保最終成品的幾何角度完全吻合 3D 模型圖面的設計要求1。 High-strength metals like 316LN inevitably exhibit a degree of angular springback after unloading from cold bending. In Ying Zhang Engineering’s practical operations, via CNC equipment setups, a springback coefficient of 1.05 to 1.15 can be precisely calculated, allowing for a 5% to 15% pre-compensatory overbend. This ensures the final product’s geometric angles flawlessly match the 3D model drawing design requirements1.
  3. 極致的內部潔淨度防護 / Ultimate Internal Cleanliness Protection：進氣霧化系統的末端連接著極精密的高壓微米噴嘴。傳統氬銲若背面充氣（Backing gas）控制不當，極易在管內殘留銲渣（Slag）與氧化物，一旦剝落就會堵塞噴嘴。而冷彎製程完全在常溫工廠內進行，無高溫熔融帶來的污染風險，提供了最高級別的管內潔淨度，徹底保障了泵浦與噴嘴的安全運作1。 The tail end of the inlet fogging system connects to ultra-precise, high-pressure micron nozzles. Traditional TIG welding, if backing gas control is flawed, easily leaves slag and oxides inside the pipe; once flaked off, these will clog the nozzles. The cold bending process, conducted entirely in a room-temperature factory, poses zero contamination risks from high-temperature melting, offering the highest level of internal pipe cleanliness and completely safeguarding the safe operation of pumps and nozzles1.
  4. 擺脫缺工危機與物料精簡 / Escaping the Labor Shortage Crisis and Material Streamlining：在當前缺工嚴峻的營建環境下，傳統工法極度依賴高階銲工的手工技藝。潁璋工程利用機台參數化設定與自動拉彎成型，成功將勞力密集的工序轉換為自動化的工廠製程。這不僅省下了採購5D 彎頭、昂貴合金銲材與保護氣體的物料成本，更將單一節點的施工時間從「數天」大幅壓縮至「數十分鐘」，達成了專案成本與排程的極致優化2。 In the current severely labor-short construction environment, traditional methods depend heavily on the manual craftsmanship of high-tier welders. Ying Zhang Engineering utilizes parametrized machine setups and automated draw-bending, successfully converting labor-intensive procedures into automated factory processes. This not only spares the material costs of purchasing 1.5D elbows, pricey alloy consumables, and shielding gases, but also heavily compresses single-node construction times from “days” to mere “tens of minutes,” achieving the ultimate optimization of project costs and schedules2.
評估項目 / Evaluation Item 傳統 1.5D 銲接彎頭工法 / Traditional 1.5D Welded Elbow Method 3D/5D 冷作彎管工法 (潁璋工程實績) / 3D/5D Cold Bending (Ying Zhang Eng. Track Record) 專案綜合效益差異 / Comprehensive Project Benefit Variance
物料與耗材 / Materials & Consumables 需額外採購銲接彎頭、大量惰性氣體與高昂合金銲材4 / Requires extra procurement of elbows, mass inert gases, and pricey alloy consumables4 僅需採購直線管材，無額外接頭與銲材2 / Only requires straight pipes, no extra fittings/consumables2 物料採購與倉儲管理成本大幅降低 / Massive reduction in material procurement and warehousing costs
人工與排程 / Labor & Scheduling 繁瑣工序，極度依賴高階銲工的手工技藝4 / Tedious procedures heavily reliant on manual welder skills4 CNC 參數設定、精確補償彈性回彈並自動拉彎成型1 / CNC setup, exact springback compensation, automated draw-bending1 施工時間由數天壓縮至數十分鐘，徹底擺脫缺工危機 / Construction slashed from days to minutes, escaping labor shortages
品質檢驗(NDT) / Quality Insp. (NDT) 高壓管線需執行 100% RT/UT，不合格需耗時剷修重銲2 / High-pressure pipe needs 100% RT/UT; failures need costly repairs2 無銲道，歸零 RT/UT 檢測費用；僅需量測橢圓度與公差2 / Weld-free, zeros RT/UT costs; only requires ovality/tolerance checks2 消滅檢測排程瓶頸，提升建廠專案的如期完工率 / Eliminates NDT schedule bottlenecks, boosting on-time completions
物理幾何控制 / Physical Geo. Control 易產生內部銲渣，影響流體純度與噴嘴壽命 / Prone to internal slag, affecting fluid purity and nozzle life 管壁減薄精確預測（< 10%），橢圓度嚴控於 2.5% 內 / Thinning precisely predicted (< 10%), ovality strictly kept under 2.5% 流體阻力降至最低，水質無銲渣污染風險4 / Minimized fluid resistance, zero risk of water slag contamination4

表 3：傳統銲接工法與冷作彎管工法之工程與經濟效益對比 / Table 3: Engineering and Economic Benefit Comparison between Traditional Welding and Cold Bending Methods

五、 結論與建議 / 5. Conclusion and Recommendations

本研究針對台灣複循環發電廠進氣霧化冷卻系統的高壓附屬管線，自應力規範理論的演進、動態疲勞分析的模擬、物理冶金機制的探討，一路貫穿至實務工程經濟的落實，進行了全方位的整合性評估。綜整所有的文獻數據、模擬分析與實務成果，獲致以下三點具體結論與實務建議：

This study conducted an all-encompassing integrated evaluation of the high-pressure auxiliary piping for inlet fogging cooling systems in Taiwan’s combined cycle power plants, piercing through from the evolution of stress code theories, dynamic fatigue analysis simulations, and physical metallurgy mechanisms, all the way to practical engineering economic implementations. Consolidating all literature data, simulation analyses, and practical results, the following three specific conclusions and practical recommendations were reached:

  1. 強制轉換至 ASME B31J 規範進行應力校核，拒絕虛假的力學安全感 / Mandate Transition to ASME B31J for Stress Verification, Rejecting False Mechanical Security： 傳統過度依賴 ASME B31.1 或3 附錄 D 簡化圖表的分析模式，已證實在處理大徑厚比管件及現代複雜幾何時存在嚴重的應力低估現象。針對長期承受高頻水錘與震動的進氣霧化高壓管線，工程單位（如 EPC 統包商及台灣電力公司）應於採購與設計規範中明確強制導入 B31J，進行應力強度因子（SIF）與扭轉撓性的重新計算。唯有如此，方能真實反映幾何不連續處的應力集中潛勢，做到防患於未然。 The traditional analytical mode over-reliant on the simplified charts of ASME B31.1 or B31.3 Appendix D has been proven to severely underestimate stresses when handling large D/t ratio fittings and modern complex geometries. For high-pressure inlet fogging piping chronically enduring high-frequency water hammer and vibration, engineering entities (like EPC contractors and Taipower) should explicitly mandate the introduction of B31J in procurement and design specs to recalculate Stress Intensification Factors (SIF) and torsional flexibilities. Only by doing so can the true stress concentration potential at geometric discontinuities be reflected, ensuring preventive preparedness.
  2. 徹底摒棄 321/347H 迷思，確立 316LN 於海岸電廠的標準材料地位 / Completely Discard the 321/347H Myth, Establishing 316LN as the Standard Material for Coastal Power Plants： 面對台灣西海岸惡劣的氯化鈉微粒侵襲，傳統用於防範高溫敏化作用的 321 與 347H 不銹鋼毫無招架之力，極易引發致命的孔蝕與應力腐蝕破裂（SCC）。316LN 憑藉著高達 25 以上的 PREN 值，以及由氮合金化帶來的優異降伏強度與高層錯能，成為唯一能同時抵禦海岸氯鹽腐蝕與水錘強大暫態力的高階合金。未來的高壓冷水系統建置，應一律採用 316LN 或同等耐蝕與強度的合金材質。 Facing the brutal sodium chloride particulate invasions on Taiwan’s west coast, the 321 and 347H stainless steels traditionally used to prevent high-temperature sensitization are utterly defenseless, highly susceptible to triggering fatal pitting and Stress Corrosion Cracking (SCC). 316LN, resting upon a PREN value exceeding 25, alongside outstanding yield strength and high stacking fault energy brought by nitrogen alloying, emerges as the sole high-grade alloy capable of simultaneously resisting coastal chloride corrosion and immense water hammer transient forces. Future high-pressure cold water system deployments should uniformly adopt 316LN or alloys of equivalent corrosion resistance and strength.
  3. 全面推廣 3D/5D 冷作彎管工法，實現力學極致與經濟效益的雙贏 / Comprehensively Promote 3D/5D Cold Bending Methods, Achieving a Win-Win in Mechanical Extremes and Economic Benefits： CAE 模擬明確指出，營運方指定的大半徑冷作彎管能將 SIF 值降至理論極限值0，使其在 Markl 疲勞曲線上的壽命表現呈現指數級別的躍升，徹底根絕傳統 1.5D 銲接彎頭的疲勞弱點。與此同時，本土的實務經驗（如潁璋工程）已充分驗證，冷作彎管工法能透過 CNC 參數設定精準消除熱影響區（HAZ），並將原本高昂的人工銲接成本與曠日費時的非破壞檢測（RT/UT）完全歸零。在妥善控制管壁減薄率與 2.5% 橢圓度極限的前提下，冷作彎管大幅壓縮了專案時程，並實現了成本結構的最佳化2。 CAE simulations explicitly indicate that large-radius cold bends designated by operators can reduce SIF values to the theoretical limit of 1.0, enabling exponential leaps in lifespan performance mapped on the Markl fatigue curve and completely eradicating the fatigue weaknesses of traditional 1.5D welded elbows. Simultaneously, local practical experience (e.g., Ying Zhang Engineering) fully validates that cold bending can precisely eliminate Heat-Affected Zones (HAZ) via CNC parameter settings while zeroing out exorbitant manual welding costs and time-consuming NDT (RT/UT). Provided wall thinning rates and the 2.5% ovality limit are properly controlled, cold bending vastly compresses project schedules and realizes optimized cost structures2.

對於大潭、通霄、興達等承擔全台供電調度重任的大型燃氣電廠而言，進氣霧化系統的妥善率直接關乎夏季尖峰的發電命脈。將「B31J 精確規範」、「316LN 耐蝕高強材料」與「冷作彎管一體化工法」三者完美結合，不僅是對抗水錘與鹽霧雙重威脅的工程正解，更是引領台灣發電產業管線設計邁向高可靠度與極致經濟效益的關鍵里程碑。 For large gas-fired power plants like Datan, Tongxiao, and Hsinta, which bear the heavy responsibility of island-wide power dispatch, the availability rate of the inlet fogging system directly dictates the lifeblood of summer peak generation. Flawlessly combining “Precision B31J Codes”, “Corrosion-Resistant High-Strength 316LN Material”, and “Integral Cold Bending Methods” is not merely the correct engineering answer for combating the dual threats of water hammer and salt spray; it is the crucial milestone steering Taiwan’s power generation piping design toward high reliability and ultimate economic benefits.

參考文獻

  1. About – 潁璋工程興業有限公司, https://yz-pipe-bending.com.tw/about/
  2. 冷作彎管之配管工程化 – 潁璋工程興業有限公司, https://yz-pipe-bending.com.tw/test/
  3. 潁璋工程興業有限公司– 冷作彎管, https://yz-pipe-bending.com.tw/
  4. 潁璋工程5CLR冷作彎管配管 – YouTube, https://www.youtube.com/watch?v=N0hnldEFIzg
  5. 建璋機械工程有限公司(潁璋工程興業有限公司) – 1111商搜網, https://trade.1111.com.tw/Comp_Info.aspx?vNo=134192
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