The ASME BPVC Section VIII Div. 1 and Div. 2 categorised weld joints , which is crucial for radiographic testing, determining weld joint efficient, and specifying the type of weld for each joint.
The therm “Category” as used refers to the location of a joint within a pressure vessel, rather than the type of joint.
Section VIII Div. 1 UW-3 defines together with Div. 2 table 4.2.1 six categories:
Category A
Longitudinal and spiral welded joints within the main shell, communicating chambers, transitions in diameter, or nozzles; any welded joint within asphere, within a formed or flat head, or within the side plates (see note 2) of a flat‐sided vessel; any butt-welded joint within a flat tubesheet; circumferential welded joints connecting hemispherical heads to main shells, to transitions in diameters, to nozzles, or to communicating chambers.
Category B
Circumferential welded joints within the main shell, communicating chambers (see note 1), 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.
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 Figure UW-3.)
Category C
Welded joints connecting flanges, lap joint stub ends, tube sheets, or flat heads to main shell, to formed heads, to transitions in diameter, to nozzles, or to communicating chambers any welded joint connecting one side plate to another side plate of a flat‐sided vessel.
Category D
Welded joints connecting communicating chambers or nozzles to main shells, to spheres, to transitions in diameter, to heads, to diffusion-welded plate packs, 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).
Category E
Welded joints at attached non-pressure parts for stiffeners and supports e.g. lifting lugs, saddle, and legs.
Category F
Welded joints connecting tubes to tube-sheets per UW-20 and limited by Figures at UW-20.1 and UW-20.2. ASME BPVC Division 2 takes the lead for Tube to Tubesheet weld categorisation
Note 1:
Communicating chambers are defined as appurtenances to the vessel which intersect the shell or heads of a vessel and form an integral part of the pressure-containing enclosure, e.g., sumps.
Note 2:
Side plates of a flat‐sided vessel are defined as any of the flat plates forming an integral part of the pressure-containing enclosure.
Table UW-12 provides an overview of which weld categories can be selected with specific requirements and a specific scope of testing for selected maximum efficiency factors.
