摘要 / Abstract
在全球能源轉型與淨零碳排的政策驅動下，台灣的複循環發電廠（Combined Cycle Power Plant, CCPP）正經歷前所未有的技術升級與運轉模式轉換。為配合再生能源的間歇性特徵，現代CCPP機組已從傳統的長期基載穩定運轉，急遽轉變為頻繁啟停（Two-shifting）與深度調峰的動態運轉。這種交變熱應力與機械疲勞，對廠內的高能管線系統（High-Energy Piping, HEP）造成了極大的損傷風險。為承受高達600°C以上的超臨界運轉溫度與極高壓力，CCPP廣泛採用了ASTM A335 P91與P92等潛變強度強化鐵素體鋼（Creep Strength Enhanced Ferritic Steels, CSEF）。在嚴苛的服役環境中，傳統1.5D對銲彎頭（Butt-Welding Elbow）因其固有的幾何應力集中與流動加速腐蝕（FAC）問題，正逐漸被特定規格之冷作彎管（2.5”~8”管徑採用3D彎管，2”及以下管徑採用5D彎管）所取代。
Under the policy drive of global energy transition and net-zero carbon emissions, Combined Cycle Power Plants (CCPP) in Taiwan are experiencing unprecedented technological upgrades and operational shifts. To accommodate the intermittent nature of renewable energy, the operational mode of modern CCPP units has rapidly transitioned from traditional long-term stable baseload operation to dynamic operations characterized by frequent two-shifting and deep peak shaving. Such alternating thermal stress and mechanical fatigue pose significant damage risks to the plant’s High-Energy Piping (HEP) systems. To withstand supercritical operating temperatures exceeding 600°C and extreme pressures, CCPPs have widely adopted Creep Strength Enhanced Ferritic Steels (CSEF) such as ASTM A335 P91 and P92. In these severe service environments, traditional 1.5D butt-welding elbows, due to their inherent geometric stress concentration and Flow-Accelerated Corrosion (FAC) issues, are gradually being replaced by specific specifications of cold bends (3D bends for 2.5”~8” pipe diameters, and 5D bends for 2” and under).
然而，在工程總承包（EPC）的實務執行中，前端3D配管設計與後端Spool（管線預製組件）製造及現場施工之間，卻存在著巨大的「鴻溝與隔閡」。配管設計師往往受限於傳統「彎頭銲接工法」的空間思維與軟體預設邏輯，導致產出的管線等角圖（ISO圖）在實體製造時，面臨彎管機夾持段長度不足、無法冷彎的窘境。同時，現場斷點（Break Point）的設置若未能考量冷彎後的彈性回彈、橢圓度與壁厚減薄，將導致現場管口組裝發生嚴重的幾何錯位，引發施工災難。本研究深入剖析ASME B31.1動力管線規範與ASME B31J應力分析標準，結合旋轉拉彎（Rotary Draw Bending）的固體力學物理邊界，以及P91/P92材料的微觀冶金熱處理限制，系統性探討此一基於管徑分級之設計與施工困局的根本原因，並提出從3D CAD軟體參數化設置到Spool模組化最佳化的整合策略。
However, in the practical execution by Engineering, Procurement, and Construction (EPC) contractors, a massive “gap and disconnect” exists between front-end 3D piping design and back-end Spool (prefabricated piping component) manufacturing and site construction. Piping designers are often constrained by the spatial mindset of traditional “elbow welding methods” and software default logics. Consequently, the generated piping isometric drawings (ISO drawings) frequently face situations where the clamping length of the bending machine is insufficient, making cold bending physically impossible. Meanwhile, if the placement of field break points fails to account for springback, ovality, and wall thinning post-cold bending, severe geometric mismatches during on-site pipe alignment will occur, triggering construction disasters. This study deeply analyzes the ASME B31.1 Power Piping Code and ASME B31J stress analysis standard, combined with the solid mechanics physical boundaries of CNC Rotary Draw Bending and the microstructural metallurgical heat treatment limits of P91/P92 materials. It systematically explores the root causes of this design and construction dilemma based on pipe size classification, and proposes integrated strategies ranging from parameterized 3D CAD software settings to optimized spool modularization.
一、 緒論與台灣CCPP產業背景 / I. Introduction and Taiwan’s CCPP Industry Background
1.1 高能管線系統面臨的動態運轉挑戰 / 1.1 Dynamic Operational Challenges Faced by High-Energy Piping Systems
隨著再生能源併網比例的大幅增加，台灣電力系統對電網穩定性的要求日益嚴苛。複循環發電廠因具備快速升降載的特性，成為調節電網頻率的主力。然而，頻繁的啟動與停機使得廠內的主蒸氣（Main Steam）、高溫再熱（Hot Reheat）及低溫再熱蒸氣等高能管線，長期暴露於極端的熱疲勞與潛變（Creep）耦合破壞機制中1。根據EPRI（美國電力研究院）的評估報告指出，高能管線系統的失效模式主要包含潛變破裂、熱疲勞、潛變-疲勞交互作用以及微觀組織不穩定性1。
With the significant increase in the grid connection ratio of renewable energy, Taiwan’s power system demands ever-stricter grid stability. Due to their rapid load-following capabilities, CCPPs have become the main force for regulating grid frequency. However, frequent startups and shutdowns expose high-energy piping—such as Main Steam, Hot Reheat, and Cold Reheat steam lines—to extreme coupled failure mechanisms of thermal fatigue and creep over the long term1. According to assessment reports by EPRI (Electric Power Research Institute), the primary failure modes of high-energy piping systems include creep rupture, thermal fatigue, creep-fatigue interaction, and microstructural instability1.
為了提升熱效率並延長設備壽命，工程界大量導入了P91（9Cr-1Mo-V）與P92（9Cr-2W-V）等潛變強度強化鐵素體鋼。這類材料藉由添加微量合金元素，在微觀組織中形成細小的碳氮化物，有效釘扎（Pinning）晶界，賦予其卓越的高溫潛變抗性3。但相對地，這些高合金鋼材對熱輸入極度敏感，其銲接熱影響區（HAZ）的細晶區或相間臨界區極易發生微觀組織劣化，在長期服役後誘發致命的第四型潛變破裂（Type IV Cracking）2。原位數位影像相關（DIC）應變量測證實，局部潛變應變會高度集中於這些弱化區域，最終導致宏觀裂紋的萌生1。
To improve thermal efficiency and extend equipment lifespan, the engineering sector has heavily adopted Creep Strength Enhanced Ferritic Steels (CSEF) such as P91 (9Cr-1Mo-V) and P92 (9Cr-2W-V). By adding trace alloying elements, these materials form fine carbonitrides in their microstructures, effectively pinning grain boundaries and granting exceptional high-temperature creep resistance3. Conversely, these high-alloy steels are extremely sensitive to heat input. The fine-grained or intercritical regions of their Heat-Affected Zones (HAZ) are highly susceptible to microstructural degradation, inducing fatal Type IV Cracking after long-term service2. In-situ Digital Image Correlation (DIC) strain measurement confirms that local creep strain highly concentrates in these weakened zones, ultimately leading to the initiation of macroscopic cracks1.
1.2 管徑分級之「以彎代銲」策略：3D (2.5”~8”) 與 5D (2”以下) 之應用 / 1.2 “Bending Instead of Welding” Strategy Based on Pipe Size Classification: Application of 3D (2.5”~8”) and 5D (2” and under)
為有效降低銲道數量並減少應力集中，國際工程界正全面推廣「以彎代銲」的設計策略。傳統改變管線走向高度依賴1.5D對銲彎頭，每次轉彎需耗費兩道厚壁銲口，大幅推升了初始資本支出（CAPEX）與營運維護成本（OPEX）。在本研究所探討的最佳化實務中，明確定義了基於管徑分級的冷作彎管策略：To effectively reduce the number of welds and minimize stress concentration, the international engineering community is comprehensively promoting the “bend instead of weld” design strategy. Traditionally, changing pipe routing heavily relied on 1.5D butt-welded elbows, requiring two thick-walled welds per turn, which drastically inflated Initial Capital Expenditure (CAPEX) and Operational Expenditure (OPEX). In the optimized practices explored in this study, a cold bending strategy based on pipe size classification is clearly defined:
- 針對中管徑（5英吋至8英吋）： 統一採用 3D冷作彎管。此區間管線若採用5D大彎管，將佔用過多廠房空間並引發佈管干涉；採用3D彎管則能在空間限制與消除銲口之間取得完美平衡。For medium diameters (2.5” to 8”): Unanimously adopt 3D cold bends. If 5D bends were used in this range, they would occupy excessive plant space and cause severe routing interference; 3D bends achieve a perfect balance between spatial constraints and weld elimination.
- 針對小管徑（2英吋及以下）： 統一採用 5D冷作彎管。這類高壓儀表或洩水系統空間配置相對靈活，且小管徑剛性極大，採用5D大半徑能極大化其柔性，吸收主系統傳遞的位移應力。For small diameters (2” and under): Unanimously adopt 5D cold bends. These high-pressure instrumentation or drain systems have relatively flexible spatial layouts. Since small-diameter high-pressure pipes possess extreme rigidity, using a large 5D radius maximizes flexibility, allowing them to absorb displacement stresses transmitted from the main system.
相對於銲接彎頭，上述冷作彎管利用直管在常溫下透過機械應力一體成型，徹底消除了轉彎處的高風險銲口。然而，冷作彎管涉及極端塑性變形後的壁厚減薄（Wall Thinning）、截面橢圓化（Ovalization）以及殘餘應力的大量累積，必須透過精密的中頻感應彎後熱處理（IH-PBHT）來恢復材料的微觀組織與潛變壽命4。Compared to welded elbows, the aforementioned cold bends are integrally formed from straight pipes at room temperature via mechanical stress, thoroughly eliminating high-risk welds at the turns. However, cold bending involves extreme plastic deformation leading to wall thinning, cross-sectional ovalization, and a massive accumulation of residual stress. It is imperative to perform precise Induction Heating Post-Bend Heat Treatment (IH-PBHT) to restore the material’s microstructure and creep life4.
二、 傳統對銲彎頭與3D/5D冷作彎管之設計哲學與力學差異 / II. Design Philosophy and Mechanical Differences Between Traditional Butt-Welded Elbows and 3D/5D Cold Bends
2.1 ASME B31.1動力管線與B31.3製程管線的風險管理哲學差異 / 2.1 Risk Management Philosophy Differences Between ASME B31.1 Power Piping and B31.3 Process Piping
台灣CCPP廠必須嚴格遵守ASME B31.1《動力配管規範》5。相較於石化廠常用的B31.3，B31.1面對高溫、高壓且具高能量釋放風險的流體，採取了極度保守的「規定性」與「厚度導向」設計7。其基本安全係數為4.0（B31.3為3.0）7，且針對超過750°F的高能管線，強制要求超音波測厚（UT）驗證。這使得冷作彎管（尤其是減薄率較高的2.5”~8” 3D彎管）的壁厚控制成為核心難點8。Taiwan’s CCPPs must strictly adhere to the ASME B31.1 Power Piping Code5. Compared to B31.3 commonly used in petrochemical plants, B31.1 adopts a highly conservative, “prescriptive,” and “thickness-oriented” design when dealing with high-temperature, high-pressure fluids that carry high energy release risks7. Its basic factor of safety is 4.0 (compared to 3.0 for B31.3)7, and it mandates Ultrasonic Testing (UT) thickness verification for high-energy piping exceeding 750°F. This makes wall thickness control of cold bends (especially the 2.5”~8” 3D bends with higher thinning rates) a core challenge8.
2.2 應力加強因子（SIF）與柔性因子（k）的物理意義 / 2.2 Physical Significance of Stress Intensification Factor (SIF) and Flexibility Factor (k)
隨著ASME B31J標準的導入，應力預測模型被大幅精細化4。傳統1.5D彎頭因轉彎半徑小，在內外弧側會產生顯著的幾何應力集中，SIF值遠大於1.0，成為疲勞壽命的脆弱節點4。相反地，2”以下的5D冷作彎管SIF趨近於完美的1.0（等同直管），幾乎不會產生額外的應力集中；而2.5”~8”的3D彎管SIF雖略高，但較1.5D彎頭已大幅下降。此外，冷作彎管成型時產生的截面橢圓化（Ovalization）效應，賦予其大於1的柔性因子（k > 1），顯著提升了吸收熱膨脹應力的能力4。With the implementation of the ASME B31J standard, stress prediction models have been vastly refined4. Traditional 1.5D elbows, due to their small turning radii, generate significant geometric stress concentration at the intrados and extrados. Their SIF values are well above 1.0, making them vulnerable nodes for fatigue life4. Conversely, 5D cold bends for 2” and under have SIFs approaching a perfect 1.0 (equivalent to straight pipe), generating almost no extra stress concentration; while 3D bends for 2.5”~8” have slightly higher SIFs, they are still significantly lower than 1.5D elbows. Furthermore, the cross-sectional ovalization effect generated during cold forming endows them with a flexibility factor greater than 1 (k > 1), significantly enhancing their ability to absorb thermal expansion stresses4.
2.3 流場擾動與流動加速腐蝕（FAC）的根絕 / 2.3 Elimination of Flow Disturbance and Flow-Accelerated Corrosion (FAC)
當超臨界蒸氣流經1.5D小半徑彎頭時，會形成強烈的「狄恩渦流（Dean Vortices）」，增加局部剪切應力並剝離保護性氧化層，引發流動加速腐蝕（FAC）5。改採3D或5D冷作彎管後，平順的幾何過渡有效抑制了二次流的生成，從物理機制上徹底根絕了FAC的發生條件，顯著延長了管線的安全服役壽命。When supercritical steam flows through a small-radius 1.5D elbow, it forms intense “Dean Vortices,” increasing local shear stress and stripping the protective oxide layer, triggering Flow-Accelerated Corrosion (FAC)5. By switching to 3D or 5D cold bends, the smooth geometric transition effectively suppresses the generation of secondary flows, completely eradicating the conditions for FAC to occur from a physical mechanism standpoint, significantly extending the safe service life of the pipeline.
三、 數位設計與實體製造的鴻溝：Spool無法冷彎之物理邊界 / III. The Gap Between Digital Design and Physical Fabrication: Physical Boundaries Preventing Spool Cold Bending
3.1 數控旋轉拉彎（CNC Rotary Draw Bending）的運動學與夾持限制 / 3.1 Kinematics and Clamping Limits of CNC Rotary Draw Bending
為克服P91厚壁合金鋼極高的屈服強度，數控旋轉拉彎機（包含彎曲模、夾具模、壓力模及內部心軸）必須施加極大的拉拔力，迫使管材沿半徑發生塑性變形8。這衍生出最不可妥協的物理邊界：「直段夾持長度（Clamp Length）」與「彎管間距（Distance Between Bends, DBB）」8。為防止管材打滑或夾傷，最小直段夾持長度至少須為管外徑的2至3倍。這意味著對於8”的3D彎管，夾持長度高達16”至24”（400mm~600mm）；若設計時間距不足，實體加工時夾具將嚴重干涉。To overcome the extremely high yield strength of P91 thick-walled alloy steel, CNC rotary draw bending machines (comprising bend dies, clamp dies, pressure dies, and internal mandrels) must exert massive pulling forces to force the pipe to plastically deform along the radius8. This gives rise to the most uncompromising physical boundaries: “Clamp Length” and “Distance Between Bends (DBB)”8. To prevent pipe slipping or clamping damage, the minimum straight clamp length must be at least 2 to 3 times the pipe’s outer diameter. This means for an 8” 3D bend, the clamp length reaches 16” to 24” (400mm~600mm); if the design lacks sufficient spacing, the clamps will severely interfere during physical fabrication.
3.2 3D CAD軟體的「剛體悖論」與設計盲區 / 3.2 The “Rigid Body Paradox” and Design Blind Spots in 3D CAD Software
導致Spool無法冷彎的元兇，往往在於EPC前端3D配管軟體（如AVEVA E3D、Smart3D）的使用習慣。系統最初建立在將管件視為不變形的「剛體」思維上。許多設計師雖將屬性改為3D或5D彎管，卻依然在極短距離內頻繁轉彎。更甚者，CAD管理員為求繪圖便利，常關閉系統內建的「管線彎曲可製造性規則」（包含最小切線長度設定），導致輸出的ISO圖在製造廠根本無法放入彎管機加工。The culprit behind spools that cannot be cold-bent often lies in the usage habits of front-end 3D piping software (e.g., AVEVA E3D, Smart3D) by the EPC. The systems were originally built on the mindset of treating fittings as undeformable “rigid bodies.” Many designers, despite changing attributes to 3D or 5D bends, still make frequent turns over extremely short distances. Even worse, CAD administrators often disable the built-in “Pipe Bending Manufacturability Rules” (which includes minimum tangent length settings) for the sake of drafting convenience, resulting in output ISO drawings that simply cannot be loaded into a bending machine at the fabrication shop.
3.3 壁厚減薄與洛倫茲因子（Lorentz Factor）的規範約束 / 3.3 Normative Constraints of Wall Thinning and Lorentz Factor
在強大彎矩下，彎管內弧側因壓縮增厚8，而外弧側會拉伸減薄，且最終厚度必須滿足設計內壓公式8。根據實務經驗，2”以下的5D彎管減薄可控制在10%以內8；但2.5”~8”的3D彎管外側減薄可能急遽增加至21%以上。ASME B31.1引入了洛倫茲因子（Lorentz Factor, I）來量化幾何對應力的局部放大效應8：Under immense bending moments, the intrados thickens due to compression8, while the extrados undergoes tensile thinning, and the final thickness must satisfy the design internal pressure formula8. Based on practical experience, thinning in 5D bends for 2” and under can be controlled within 10%8; however, outer thinning for 2.5”~8” 3D bends can sharply increase to over 21%. ASME B31.1 introduces the Lorentz Factor (I) to quantify the local amplification effect of geometry on stress8:
Iextrados=(4(R/D)+1)/(4(R/D)+2)
（D 為管外徑8）。這意味著對於減薄嚴重的3D彎管，設計師在開立材料清單（MTO）時，必須預先採購具備足夠餘裕的特厚管材（如XXS等級），以避免測厚不合格而報廢8。(Where D is the pipe outer diameter8). This implies that for 3D bends with severe thinning, designers must proactively procure extra-heavy wall pipes (such as XXS schedule) when generating the Material Take-Off (MTO) to avoid rejection due to failing thickness tests8.
3.4 資深設計師的空間邏輯與現場銲接空間之考量 / 3.4 Spatial Logic of Senior Designers and Consideration of Field Welding Space
當資深配管設計師在3D軟體中佈置管線時，其思維模式與過度依賴軟體自動化的初階工程師有著本質上的不同。真正的實務設計絕非僅是讓3D軟體跑完干涉檢查、直接產出ISO圖後便「丟給現場單位」施工。資深設計師深知，冷作彎管的現場斷點（Field Weld, FW）設置，必須將「現場銲口的施工位置」與「銲接操作空間」納入核心考量。他們會具體評估現場人員是否有足夠的立足點搭設施工架、是否有充裕的空間進行氬銲（TIG）打底與後續的非破壞檢測（NDT）。特別是對於P9x這類需進行嚴苛中頻感應加熱（IH-PBHT/PWHT）的高合金管線，若斷點設在過於狹窄的管廊內部或緊貼鋼構樑柱，將導致加熱線圈與保溫棉無法纏繞施作。因此，資深設計師會主動介入軟體的自動分段邏輯，在考量彎管機夾持極限值與運輸吊裝尺寸的同時，手動優化Spool的斷點位置，為現場銲接與熱處理保留絕對的施作餘裕。When senior piping designers route pipelines in 3D software, their mindset fundamentally differs from junior engineers who overly rely on software automation. True practical design is never merely about letting the 3D software complete clash checks, directly generating ISO drawings, and then “throwing them at the field unit” for construction. Senior designers are well aware that the placement of Field Welds (FW) for cold bends must incorporate the “construction location of the field weld” and “welding operational space” as core considerations. They concretely evaluate whether site personnel have sufficient footholds to erect scaffolding, and whether there is ample clearance for TIG root passes and subsequent Non-Destructive Testing (NDT). Especially for high-alloy pipelines like P9x that require stringent medium-frequency induction heating (IH-PBHT/PWHT), if a break point is set inside an excessively cramped pipe rack or too close to structural steel beams, it will be impossible to wrap the heating coils and insulation blankets. Therefore, senior designers actively intervene in the software’s automatic spooling logic. While accounting for the clamping limits of the bending machine and transport/lifting dimensions, they manually optimize the break point locations of the Spool to reserve absolute operational margins for field welding and heat treatment.
四、 現場斷點（Break Point）銲接困境與幾何變形之耦合分析 / IV. Coupling Analysis of Break Point Welding Dilemmas and Geometric Deformation
4.1 橢圓度（Ovality）的蔓延與切線斷點的災難 / 4.1 The Spread of Ovality and the Disaster of Tangent Line Break Points
若配管設計師依循傳統思維，將現場銲口設置在緊貼彎管切線（Tangent Line）的位置，將引發嚴重問題。因為傳統鍛造彎頭在出廠前已經車床加工呈現完美的正圓幾何，但冷作彎管脫離機台後會產生彈性回彈（Springback），使得切線外側的直管段依然殘留顯著的橢圓度8。即便彎管符合高能系統5%以內的橢圓度規範8，現場人員仍必須面對一個「橢圓形的管口」。If piping designers follow traditional thinking and set the Field Weld precisely at the Tangent Line of the bend, severe problems arise. While traditional forged elbows are machined to perfect circular geometry before leaving the factory, cold bends experience springback after being released from the machine, leaving significant residual ovality in the straight pipe section just outside the tangent8. Even if the bend complies with the strict 5% ovality code for high-energy systems8, site personnel are still forced to deal with an “elliptical pipe end.”
4.2 錯邊量（Hi-Lo Mismatch）與強制組對的殘餘應力 / 4.2 Hi-Lo Mismatch and Residual Stress from Forced Alignment
將正圓直管對接到橢圓形斷點時，會產生嚴重的錯邊量（Hi-Lo Mismatch）。要將高屈服強度的P91合金鋼管（尤其是8英吋XXS厚度的3D彎管）在現場強制校正成正圓幾乎不可能。即便強行組對，導入的巨大殘餘應力也極易誘發銲道凝固裂紋，並在商轉後成為引爆管線破裂的定時炸彈1。這正是現場施工單位極度排斥冷作彎管的痛點。Attempting to mate a perfectly round straight pipe to an elliptical break point results in severe Hi-Lo mismatch. Forcibly correcting a high-yield-strength P91 alloy steel pipe (especially an 8-inch, XXS thickness 3D bend) into a perfect circle on-site is virtually impossible. Even if forcibly aligned, the massive residual stress introduced is highly likely to induce solidification cracking in the weld and become a ticking time bomb for pipe rupture after commercial operation1. This is the exact pain point why site construction units strongly resist cold bends.
五、 高能管線（P91/P92）冷彎之微觀冶金劣化與破壞力學邊界 / V. Microstructural Degradation and Fracture Mechanics Boundaries of P91/P92 High-Energy Piping Cold Bending
5.1 纖維伸長率（Fiber Elongation）與強制PBHT極限值 / 5.1 Fiber Elongation and Mandatory PBHT Thresholds
最大纖維伸長率估算公式為：ϵ(%)=50⋅D/R （其中 D 為管外徑，R 為彎曲中心線半徑）8。針對P91/P92材料，ASME強制規定當應變率超過5%時，必須進行彎後熱處理（PBHT）4。代入本研究設定，3D彎管應變率約為16.67%，5D彎管為10%，皆遠超5%的豁免極限值。若未經熱處理，材料內部的高密度差排將導致潛變抗力徹底崩潰1。The maximum fiber elongation is estimated by the formula: ϵ(%)=50⋅D/R (Where D is the pipe outer diameter and R is the bend centerline radius)8. For P91/P92 materials, ASME mandates Post-Bend Heat Treatment (PBHT) when the strain rate exceeds 5%4. Substituting this study’s settings, the strain rate for a 3D bend is approximately 16.67%, and 10% for a 5D bend, both far exceeding the 5% exemption threshold. Without heat treatment, the high-density dislocations within the material will cause a complete collapse of creep resistance1.
5.2 AC1與AC3相變溫度的精密掌控與潛變壽命毀滅 / 5.2 Precise Control of Ac1/Ac3 Phase Transformation Temperatures and Destruction of Creep Life
P91鋼材的下臨界相變溫度（AC1）約為800°C~830°C，上臨界相變溫度（AC3）則位於890°C至940°C。ASME 2025版規範嚴格限制最高熱處理溫度不得超過770°C。若中頻感應加熱（IH-PBHT）發生溫度過衝跨越AC1進入雙相區，原始強化的析出相將溶解，轉變為多邊形鐵素體或未回火的脆性麻田散鐵，導致材料潛變壽命從100,000小時銳減至20,000小時以下。因此，業界需強制導入相控陣超音波（PAUT）與硬度測試以確保品質。The lower critical phase transformation temperature (AC1) of P91 steel is approximately 800°C~830°C, while the upper critical phase transformation temperature (AC3) is between 890°C and 940°C. The 2025 edition of ASME codes strictly limits the maximum heat treatment temperature to no more than 770°C. If induction heating (IH-PBHT) experiences temperature overshoot crossing AC1 into the intercritical region, the originally strengthened precipitates will dissolve and transform into blocky ferrite or untempered brittle martensite, causing the material’s creep life to plummet from 100,000 hours to under 20,000 hours. Consequently, the industry mandates Phased Array Ultrasonic Testing (PAUT) and hardness testing to ensure quality.
5.3 PBHT熱處理設備對Spool幾何形狀的反向限制 / 5.3 Geometric Reverse-Constraints on Spools Imposed by PBHT Equipment
為克服整爐熱處理的長度限制，現場多採用中頻感應加熱8。由於加熱線圈必須環繞彎管並行走於鄰近直管段8，這對Spool設計提出了反向限制：彎管兩端必須預留足夠的「直管段長度」（尤其是大型的8” 3D彎管線圈模組）。若斷點過近，線圈無法套入，PBHT將無法執行。To overcome the length limitations of furnace heat treatment, medium-frequency induction heating is often used on-site8. Because the heating coils must wrap around the bend and traverse the adjacent straight pipe8, this imposes a reverse constraint on Spool design: sufficient “straight pipe length” must be reserved at both ends of the bend (especially for the large coil modules of an 8” 3D bend). If the break point is too close, the coils cannot be fitted, rendering PBHT impossible to execute.
六、 業主、EPC與專業承包商之決策思維與實務工法效益 / VI. Decision-Making Mindsets and Practical Method Benefits of Owners, EPCs, and Specialized Contractors
6.1 業主（台電）對於選取彎管與PBHT之決策思維 / 6.1 Taipower’s Decision-Making Mindset Regarding Bending Selection and PBHT
作為最終營運方，台電的核心訴求是電廠的長期運轉安全性與極小化非預期停機機率。因此，業主在規範中強烈傾向「以彎代銲」，透過指定中管徑採用3D彎管、小管徑採用5D彎管，從根本上消除銲口缺陷風險。針對PBHT，台電要求P91在銲接或成形後，應在100°C停留1小時確保麻田散鐵轉化，並嚴格遵循極為緩慢的升降溫與保溫程序4。這種不惜增加初期時間與預算的決策，確保了高溫服役下的絕對可靠性。As the ultimate operator, Taipower’s core objective is the long-term operational safety of the plant and minimizing unscheduled downtime. Thus, the owner strongly favors “bending instead of welding” in the specifications, mandating 3D bends for medium diameters and 5D bends for small diameters to fundamentally eliminate weld defect risks. Regarding PBHT, Taipower requires P91 to be held at 100°C for 1 hour after welding or forming to ensure martensite transformation, and strictly follow an extremely slow heating/cooling and hold procedure4. This decision, which spares no expense in initial time and budget, guarantees absolute reliability under high-temperature service.
6.2 EPC承包商之工法考量 / 6.2 Method Considerations of the EPC Contractor
相對於業主看重壽命，EPC更關注專案時程與現場施工可行性。依管徑選用3D/5D彎管是EPC在「受限的廠房空間」與「減少銲口數量」之間取得的平衡。面對耗時且佔用關鍵要徑的嚴苛PBHT程序（由於P91材料要求長時間保溫4），EPC積極將彎管預製與熱處理轉移至專業製造工廠內完成，以此降低現場氣候干擾與高階銲工短缺帶來的變數。While the owner prioritizes lifespan, the EPC focuses more on project schedules and site construction feasibility. Selecting 3D/5D bends based on pipe size is the EPC’s balance between “restricted plant space” and “reducing weld counts.” Faced with the grueling PBHT procedures that consume critical path time (due to P91’s requirement for long hold times4), EPCs proactively shift bending prefabrication and heat treatment to specialized manufacturing facilities. This mitigates variables caused by on-site weather interference and the shortage of high-tier welders.
6.3 潁璋工程「三合一工法」之實務效益 / 6.3 Practical Benefits of Ying-Chang Engineering’s “Three-in-One Method”
為落實模組化策略，台灣本土專業製造商潁璋工程發展出整合ISO圖佈管最佳化、CNC機械冷作彎管，以及工廠端一體化熱處理與檢測的「三合一工法」。該工法大幅減少了傳統彎頭物料採購費用與現場對高階配管工的依賴。消除大量銲口更節省了高昂的RT檢測費用及剷修浪費，不僅有效壓縮施工時間以達到專案精準要求，更完美實現了業主與EPC所追求的成本降低與品質升級理念。To implement the modularization strategy, local Taiwanese specialist manufacturer Ying-Chang Engineering developed a “Three-in-One Method” integrating ISO drawing routing optimization, CNC mechanical cold bending, and integrated factory-side heat treatment and inspection. This method drastically reduces traditional elbow material procurement costs and reliance on high-level site pipeliners. Eliminating massive numbers of welds also saves exorbitant RT inspection costs and rework waste, effectively compressing construction time to meet exact project demands, and perfectly realizing the cost reduction and quality upgrade concepts pursued by the owner and EPC.
七、 弭平設計與施工鴻溝之整合優化策略 / VII. Integrated Optimization Strategies to Bridge the Design and Construction Gap
為徹底解決設計與施工矛盾，EPC與製造商必須進行以下跨維度整合：To completely resolve the conflicts between design and construction, EPCs and manufacturers must undertake the following cross-dimensional integrations:
7.1 導入數位雙生，嚴格配置3D CAD之可製造性規則 / 7.1 Introduce Digital Twins and Strictly Configure 3D CAD Manufacturability Rules
將彎管機台的物理極限（數位雙生）寫入3D CAD系統參考數據中：Embed the physical limits of the bending machines (digital twin) into the reference data of 3D CAD systems:
- 強制啟用「管線彎曲可製造性規則」，禁止隨意關閉。Mandate the activation of “Pipe Bending Manufacturability Rules” and prohibit bypassing.
- 依據5”~8”（3D）與2”以下（5D）特性，在系統內明確設定最小切線長度（例如 L≧ 2.5D），當DBB過短時自動阻擋圖面生成。Based on the characteristics of 2.5”~8” (3D) and 2” and under (5D), explicitly set the minimum tangent length in the system (e.g., L≧ 2.5D), automatically blocking drawing generation if DBB is too short.
- 整合SIF評估模組，讓設計師有意識地為大半徑彎管預留空間4。Integrate SIF evaluation modules to consciously guide designers in reserving space for large-radius bends4.
7.2 最佳化現場斷點（Break Point）的設計原則 / 7.2 Optimization Principles for Field Break Point Design
斷點設計必須揚棄「切線即斷點」，改採保留直管延伸段的安全策略。現場斷點應強制設置在距離切點至少 1D 至 2D 長度之外的純直管段上8，以避開橢圓變形區，降低強制校正殘餘應力；同時為後續的局部感應熱處理與超音波測厚預留操作網格帶8。Break point design must abandon “tangent equals break point” and adopt a safe strategy of retaining straight pipe extensions. Field break points must be mandatorily placed on purely straight sections at least 1D to 2D away from the tangent line to avoid the oval deformation zone and reduce residual stress from forced alignment8. Simultaneously, this reserves operational grid bands for subsequent local induction heat treatment and UT thickness measurements8.
7.3 推動基於「管徑分級」的3D/5D Spool模組化設計 / 7.3 Promoting 3D/5D Spool Modularization Based on “Pipe Size Classification”
在一根長達6公尺的XXS級無縫鋼管上，連續彎折出具備正確「彎管間距」的多維度空間彎。此舉能大量削減關鍵銲道與Type IV破裂風險，降低潛變裂紋發生機率，節省昂貴的PWHT成本4。同時能根除流場擾動確保兩相流場穩定5，並透過降低的SIF值完美契合CCPP頻繁啟停所帶來的高週次交變熱疲勞要求4。Continuously bend multidimensional spatial bends with correct “distances between bends” on a single XXS seamless steel pipe up to 6 meters long. This action drastically eliminates critical welds and Type IV cracking risks, lowers creep crack probability, and saves expensive PWHT costs4. It also eradicates flow disturbances to ensure two-phase flow stability5, and—through lowered SIF values—perfectly matches the high-level fatigue requirements of frequent CCPP cycling4.
7.4 Spool模組化的實務極限：吊裝空間與現場裁切之風險迴避 / 7.4 Practical Limits of Spool Modularization: Lifting Space and Avoidance of On-site Cutting Risks
然而，Spool的模組化設計絕非一昧地追求「一支Spool可以彎出多少個空間彎」。資深設計師深知，冷作彎管的極限並非僅受限於工廠機台的加工能力，更受限於現場複雜的安裝路徑與吊裝空間。縱使工廠端能在一根管件上連續彎折出極度複雜的多維度形狀，但若未能考量廠房鋼構的穿梭空間與吊車的作業半徑，這龐大且形狀奇異的Spool將面臨「運得到現場，卻塞不進管廊」的窘境。一旦發生此情況，現場單位將被迫把耗費鉅資完成預製與熱處理的完美Spool強行裁切，隨後再重新打坡口、組對，並增加原本極力避免的現場銲口。這不僅徹底破壞了工廠預製的品質保證，更衍生出額外的熱處理與檢測成本，使「以彎代銲」的美意弄巧成拙。因此，Spool的分段設計必須在「最大化減少銲口」與「確保現場可安裝性」之間取得精準的平衡。However, the modular design of Spools is by no means about blindly pursuing “how many spatial bends can be formed in a single Spool.” Senior designers profoundly understand that the limits of cold bending are not only constrained by the fabrication capabilities of factory machines but also by the complex installation routing and lifting space on-site. Even if the factory can continuously form extremely complex, multi-dimensional shapes on a single pipe, if the maneuvering space through plant steel structures and the operating radius of cranes are not considered, this massive and oddly shaped Spool will face the dilemma of “arriving at the site but unable to fit into the pipe rack.” Once this occurs, site units will be forced to forcefully cut the perfect Spool—which cost a fortune to prefabricate and heat-treat—on-site. They must then re-bevel, align, and add the very field welds that the design strove to avoid. This not only completely destroys the quality assurance of factory prefabrication but also incurs additional heat treatment and inspection costs, defeating the original purpose of “bending instead of welding.” Therefore, the segmentation design of Spools must strike a precise balance between “maximizing weld reduction” and “ensuring on-site installability.”
八、 結論 / VIII. Conclusion
台灣複循環發電廠（CCPP）在能源轉型下，高能管線系統面臨嚴苛挑戰。針對管徑特性採用「中管徑（2.5”~8”）3D冷作彎管」結合「小管徑（2”及以下）5D冷作彎管」，是解決高合金鋼應力集中、潛變破裂與流動加速腐蝕的最佳優化方案。若前端設計忽視固體力學極限與冶金邊界，或者初階工程師僅盲目依賴電腦產圖而忽視現場吊裝限制，必將引發無法成型與現場裁切錯位等災難。透過在CAD系統鎖定可製造性規則、讓資深設計師手動外推現場銲口以確保施工空間並權衡Spool的實體安裝尺寸，再善用「三合一工法」等專業預製策略，EPC承包商方能發揮冷作彎管終極優勢，構築安全、長壽命的新世代高能管線系統。Driven by energy transition, high-energy piping systems in Taiwan’s CCPPs face severe challenges. Adopting “medium diameter (2.5”~8”) 3D cold bends” combined with “small diameter (2” and under) 5D cold bends” tailored to pipe characteristics represents the optimal solution to high-alloy steel stress concentration, creep rupture, and flow-accelerated corrosion. If front-end designs ignore solid mechanics limits and metallurgical boundaries, or if junior engineers blindly rely on computer-generated drawings while ignoring site lifting constraints, fabrication failures and on-site cutting mismatch disasters are inevitable. By locking manufacturability rules in CAD systems, having senior designers manually extend field welds to ensure construction space and weigh the physical installation dimensions of Spools, and leveraging specialized prefabrication strategies like the “Three-in-One Method,” EPC contractors can unlock the ultimate advantages of cold bending to construct safe, long-lasting, next-generation high-energy piping systems.
參考文獻
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