压力容器、管道和储罐施工规范提供了设计规则，以确保在设计条件下不会发生脆性断裂。在启动和关闭条件下，脆性断裂的风险通常最高，因为设备可能暴露在可能的最高压力（即应力）和最低金属温度（即最低断裂韧性）事件中。为了尽量减少或消除这些影响，制定了最低增压温度（MPT）包络线，以确保在增压或减压期间具有足够的韧性。MPT封套可根据ASME B&PV规范第八节第1部分（VIII-1）第UCS-66段和第八节第2部分（VIII-2）第3部分第3.11段进行开发。本公告为根据符合API 579的断裂力学方法确定加压设备的MPT曲线提供了依据- 1/ASME FFS-1第9部分，2016版。该方法是WRC 528中用于创建ASME B&PV规范第八节第2部分toughnes豁免曲线的方法的扩展。本公告中的断裂韧性估算基于沃林断裂韧性主曲线。断裂韧性评估包括回火脆化、氢对断裂韧性的影响，并考虑了氢环境中的快速断裂和慢速断裂，因此可以为碳钢、1.25Cr-0.5Mo和2.25Cr-1Mo制造的高压氢处理容器生成MPT曲线。2.25Cr-1Mo-V、3Cr-1Mo和3Cr-1Mo-V，带或不带奥氏体不锈钢包层。还可能包括与加载速率相关的影响。MPT曲线基于API 579-1/ASME FFS-1附件9D规定的压力和残余应力产生的膜应力，以及包层的影响。为圆柱壳和球壳中的两个参考缺陷提供了解决方案: 长宽比为6的t/4和t/8深度。还提供了将在役检查期间发现的缺陷的影响纳入MPT曲线的规定。一般来说，使用本公告制定的MPT曲线允许比使用VIII-1或VIII-2代码实现的MPT曲线更低或更冷，同时保持可定义的安全裕度，从而提高启动操作的操作灵活性。温预应力（WPS）效应描述了先前加载对后续有效断裂韧性的影响。最后，提供了使用MPT模型生成豁免曲线和温度降低曲线的程序，这些曲线可纳入施工规范。文中还提供了一些问题示例来演示该技术。

Pressure vessels, piping and storage tank construction codes provide design rules to ensure that brittle fracture will not occur at design conditions. The risk of brittle fracture is typically highest during start-up and shutdown conditions because the equipment may be exposed to the highest pressure (i.e., stress) and lowest metal temperature (i.e., lowest fracture toughness) events possible. In order to minimize or eliminate these effects, a Minimum Pressurization Temperature (MPT) envelope is developed to ensure adequate toughness exists during pressurization or depressurization. MPT envelopes may be developed based on the ASME B&PV Code, Section VIII, Division 1 (VIII-1), paragraph UCS-66 and Section VIII, Division 2 (VIII-2), Part 3, paragraph 3.11.This Bulletin provides the basis to determine an MPT curve for pressurized equipment based on a fracture mechanics approach consistent with API 579-1/ASME FFS-1, Part 9, 2016 Edition. The approach is an extension of that used in WRC 528 to create the toughnes exemption curves for the ASME B&PV Code, Section VIII, Division 2. The fracture toughness estimation in this Bulletin is based on the Wallin Fracture Toughness Master Curve. The fracture toughness estimation includes temper embrittlement, hydrogen effects on fracture toughness, and considers both fast and slow fracture in hydrogen environments so that MPT curves can be generated for high-pressure hydrogen processing vessels constructed from carbon steel, 1.25Cr-0.5Mo, 2.25Cr-1Mo. 2.25Cr-1Mo-V, 3Cr-1Mo and 3Cr-1Mo-V with and without austenitic stainless steel cladding. Loading rate dependent effects may also be included. The MPT curves are based on membrane stress from pressure and residual stresses in accordance with API 579-1/ASME FFS-1, Annex 9D, and the effects of cladding. Solutions are provided for two reference flaws in cylindrical and spherical shells: t/4 and t/8 depth with an aspect ratio of six. Provisions are also provided to incorporate the effects of flaws found during in-service inspection into the MPT curve. In general, the MPT curve developed using this Bulletin permits a lower or colder MPT curve than that achievable using the VIII-1 or VIII-2 Codes while maintaining a definable safety margin, which results in increased operational flexibility for startup operations. The Warm Prestress (WPS) effect that describes the effect of a prior loading on the subsequent effective fracture toughness is also included. Finally, a procedure is provided for using the MPT model to generate exemption and temperature reduction curves that may be incorporated into construction codes. Example problems are provided to demonstrate the technology.