Terminology of Joint Category and Joint Efficiency

Joint category defines the location of a joint in a vessel and does not define the type of joint.
Categories of Joints
1. Longitudinal welds in main shell or attached nozzles, welds in a sphere, head or flatsided vessel, circumferential joints connecting hemi-heads to a vessel or part of a vessel.

2. Circumferential welds in a shell or nozzle or connecting heads other than hemiheads or part of a vessel.
3. Welds connecting flanges, tube sheets or flat heads to a vessel or part of a vessel and welds connecting flat-sided vessels.
4. Welds connecting nozzles to a vessel or part of a vessel.

Note A butt weld is defined as a weld connecting two pieces of material with surfaces that are 30 degrees or less from being in the same plane.

Types of Joints
Type defines the configurations of a welded joint. It does not define the location of the joint in the vessel. For example, Type 2 joint is a single-butt weld with a backing strip left in place.

Joint Efficiency
The joint efficiency (E) or % of stress value (S) to be used in calculating required thickness or maximum
• Type of welded joint
• Degree of radiography performed

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