Tubular T, K, and Y joints are the primary structural connection type in offshore jacket structures, process platform frameworks, and structural tubular steelwork — and among the most inspection-challenging weld geometries in industrial NDT. The curved saddle weld that forms the intersection between a brace and a chord, the varying dihedral angle around the weld circumference, and the geometric transition from crown to heel to toe of each brace create an inspection surface that varies continuously and that conventional UT cannot address with standard probe configurations.
Why TKY Welds Require PAUT
Continuous Geometric Variation
The dihedral angle between the brace and chord varies continuously from
crown to saddle around the brace circumference. At each angular position, the
optimal UT beam angle for interrogating the weld root and fusion line changes —
making a fixed-angle conventional UT probe position optimal at one location and
geometrically misaligned at an adjacent position. PAUT's electronic beam
steering adapts the active focal law to the local geometry as the scanner
traverses the weld.
Fatigue Crack Detection Priority
TKY joints in offshore structures are subject to dynamic wave and
current loading — making fatigue cracking at the weld toe the primary integrity
concern. The weld toe location, and the near-surface inspection zone where
fatigue cracks initiate and propagate, requires specific focal law attention
and surface wave or creep wave technique supplement to achieve the sensitivity
required for early-stage fatigue crack detection.
Access Constraints at Height and in Splash Zone
Offshore TKY joints are frequently located at elevation, in the splash
zone, or in partially submerged locations where access for conventional
multi-probe UT setup is impractical. PAUT scanner configurations for TKY welds
are designed for rapid setup, minimal probe position changes, and secure
fixture on curved tubular surfaces — enabling effective inspection in the
access conditions that offshore structural inspection demands.
•
Offshore jacket and topsides structural TKY weld
inspection
•
Jack-up
rig leg and spudcan connection weld examination
•
Process platform tubular structural connection
inspection
•
Onshore structural steelwork tubular joint inspection
•
Fatigue crack monitoring at TKY weld toes on high-cycle
loading structures
•
Post-weld repair TKY acceptance inspection
•
Pre-service baseline inspection of new offshore
structure TKY welds
Reports include geometry-referenced
coverage maps, encoded PAUT data at all scanner positions around the brace
circumference, indication tables with weld clock position, through-wall depth,
and defect classification, and accept/reject disposition against AWS D1.1,
DNVGL-OS-C101, or the applicable offshore structural inspection standard.