Maximum Weld Reinforcement and Weld Joint Categories in ASME Section VIII Division 1
Introduction:
ASME Section VIII Division 1 is a widely recognized code for designing and constructing pressure vessels. Within this code, specific guidelines are provided for weld reinforcement and weld joint categorization. In this blog post, we will explore the maximum weld reinforcement as per UW-35 and the four categories (A, B, C, and D) of weld joints according to UW-3 in ASME Section VIII Division 1.
Maximum Weld Reinforcement (UW-35):
Weld reinforcement refers to the excess weld metal that extends beyond the original base material surface. ASME Section VIII Division 1 provides guidance on the maximum allowed weld reinforcement in UW-35. The thickness of the weld reinforcement on each face shall not exceed the following:
A reduction in thickness due
to the welding process is acceptable provided all of the following conditions
are met:
(1) The
reduction in thickness shall not reduce the material of the adjoining surfaces
below the minimum required thickness at any point.
(2) The reduction in thickness shall not
exceed 1/32 in. (0.8 mm) or 10% of the
nominal thickness of the adjoining surface, whichever is less.
(c) When
a single‐welded butt joint is made by using a backing strip which is left
in place [Type No. (2) of Table UW-12],
the requirement for reinforcement applies only to the side opposite the backing
strip.
(d) To assure that the weld grooves are completely filled so that the surface of the weld metal at any point does not fall below the surface of the adjoining base materials weld metal may be added as reinforcement on each face of the weld.
Weld Joint Categories (UW-3):
ASME Section VIII Division 1 categorizes weld joints into four categories: A, B, C, and D, based on their quality and inspection requirements. These categories provide a framework for assessing the level of quality control and examination required for each type of weld joint.
1. Category A:
2. Category B:
Circumferential welded joints within the main shell, communicating chambers,66 nozzles, or transitions in diameter including joints between the transition and a cylinder at either the large or small end; circumferential welded joints connecting formed heads other than hemispherical to main shells, to transitions in diameter, to nozzles, or to communicating chambers.66 Circumferential welded joints are butt joints if the half‐apex angle, α, is equal to or less than 30 deg and angle joints when α is greater than 30 deg. (See above Figure.)
3. Category C:
Welded joints connecting flanges, Van Stone laps, tubesheets, or flat heads to main shell, to formed heads, to transitions in diameter, to nozzles, or to communicating chambers66 any welded joint connecting one side plate67 to another side plate of a flat‐sided vessel.
4. Category D:
Welded joints connecting communicating chambers or nozzles to main shells, to spheres, to transitions in diameter, to heads, or to flat‐sided vessels, and those joints connecting nozzles to communicating chambers (for nozzles at the small end of a transition in diameter, see Category B).
Conclusion:
Adhering to the guidelines set forth in ASME Section VIII Division 1 ensures that welds in pressure vessels are constructed with appropriate reinforcement and undergo the necessary quality control measures. The maximum weld reinforcement limits defined in UW-35 help maintain the structural integrity of welded joints, while the categorization of weld joints in UW-3 provides a framework for determining the level of quality control and inspection required for different types of welds. By following these standards, engineers and manufacturers can ensure the safe and reliable operation of pressure vessels in various industries.
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