ASME VIII-1气压试验的专项要求

UW-50 NONDESTRUCTIVE EXAMINATION OF WELDS ON VESSELS TO BE PNEUMATICALLY TESTED

(a) On welded pressure vessels to be pneumatically tested in accordance with UG-100, the following shall be examined before the pneumatic test is performed, for the purpose of detecting cracks. Examination shall be by the magnetic particle or liquid penetrant method when the material is ferromagnetic or by the liquid penetrant method when the material is nonferromagnetic.

(1) the full length of all welds around openings, accessible to surface NDE

(2) the full length of all attachment welds having a throat thickness greater than 1/4 in. (6 mm), including welds attaching nonpressure parts to pressure parts, accessible to surface NDE

(3) any area where welds having a throat thickness exceeding 1/4 in. (6 mm) have been removed

(b) The weld joint examination requirements given in (a) may be waived when the maximum allowable working pressure of the vessel is no greater than 500 psi (3.5 MPa) and the following applicable requirement is met:

(1) For Part UCS materials, the governing thickness as defined in UCS-66(a) shall be limited to a maximum governing thickness of 1/2 in. (13 mm) for materials assigned to Curve A, and 1 in. (25 mm) for materials assigned to Curve B, C, or D in Figure UCS-66 (Figure UCS-66M).

(2) For austenitic chromium–nickel stainless steels 304, 304L, 316, 316L, 321, and 347 in Part UHA, the maximum nominal material thickness shall be 3/4 in. (19 mm).

(3) For aluminum, aluminum alloy 3000 series, aluminum alloy 5000 series, and aluminum alloy 6061-T6 in Part UNF, the maximum nominal material thickness shall be 1 in. (25 mm).


一、适用范围

本条款 UW-50 是 ASME 规范中关于需进行气压试验的压力容器焊缝无损检测的专项要求，适用于按 UG-100 进行气压试验的焊接压力容器，目的是在气压试验前检测焊缝裂纹，保障试验安全。
  
二、检测方法要求

- 若容器材料为铁磁性材料：可采用 磁粉检测（MT） 或 液体渗透检测（PT）。
- 若容器材料为非铁磁性材料：仅可采用 液体渗透检测（PT）。
  
三、必须检测的焊缝区域（a 款）

在气压试验前，需对以下可进行表面无损检测的区域进行全长检测：

1. 所有开孔周围的焊缝：覆盖开孔周边焊缝的全长。
2. 焊喉厚度大于 1/4 in.（6 mm）的所有附件焊缝：包括将非受压件连接到受压件的焊缝，且需覆盖其全长。
3. 焊喉厚度超过 1/4 in.（6 mm）的焊缝被移除后的任何区域：对该区域进行检测。
  
四、检测要求的豁免条件（b 款）

当容器的最大允许工作压力（MAWP）不大于 500 psi（3.5 MPa），且满足以下对应材料类别要求时，(a) 款的焊缝检测要求可被豁免：

材料类别 适用材料 最大厚度限制
Part UCS（碳钢/低合金钢） 曲线 A 材料 1/2 in. (13 mm)
曲线 B/C/D 材料 1 in. (25 mm)
Part UHA（奥氏体不锈钢） 304/304L/316/316L/321/347 3/4 in. (19 mm)
Part UNF（铝及铝合金） 纯铝、3000/5000 系、6061-T6 1 in. (25 mm)

五、关键解读与应用提示

1. 安全优先级：气压试验的危险性远高于水压试验，因此本条款通过强制表面检测，提前发现裂纹类缺陷，避免试验中发生灾难性失效。
2. 豁免边界：豁免并非完全免除检测责任，而是在压力和厚度双重限制下，允许简化检测流程，设计时需严格核对材料曲线与厚度限制。
3. 可及性要求：所有检测区域必须满足“可进行表面无损检测”的条件，不可达区域需通过工艺设计或结构调整解决。
4. 本章节并未对接焊缝（纵焊缝、环焊缝）做要求，是否需要做100%RT/UT或全部表面检测？欢迎留言讨论

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ASME VIII-1气压试验的专项要求            

UW-50 NONDESTRUCTIVE EXAMINATION OF WELDS ON VESSELS TO BE PNEUMATICALLY TESTED

ASME VIII-1气压试验的专项要求

ASME VIII-1气压试验的专项要求

ASME VIII-1气压试验的专项要求