Maximum thickness of specimen

The maximum thickness of material (TM) that can be inspected is limited by coupling medium height  (Tc) , such as water, plexiglass, etc.

VC  => Sound velocity in coupling medium.

VM =>  Sound velocity in specimen.

Skip

distance (SD)

The “skip distance” is the surface distance from the probe "index point" where the sound beam returns to the surface. This distance must be calculated to determine the probe distance to the weld to provide full inspection coverage for the component thickness.

Probe angle =>  θ

TM  => Thickness material.

Half skip

distance

(HSD)

The “half skip distance” is the surface distance from the “probe index point” to the point on the surface above the point where the sound beam reaches the backwall of the component.

Half-skip-beam-path length (HSBPL) = AD = TM/cos θ

Full-skip-beam-path length (FSBPL) = AD + DC = 2TM/ cos θ 

Flaw

Identifications

DPL1 => Flaw depth from the surface, considering the first leg

SP => Sound path -  without reflection on the backwall

Flaw

Identifications

DPL2 => Flaw depth from the surface, considering the second leg

SP  => Sound path, including the reflection on the backwall

TM => Material thickness

Testing round parts

Relationship between wedge length and part radius

It is recommended, for contact inspections, that if the wedge is not shaped, the wedge length (LWedge)meets the following condition

=> Rpart: Outer radius

As a rule of thumb, the height between the wedge extremes and the round part must be ≤ 0.5mm

Ultrasonic

examination of an axial weld pipe

The ultrasonic beam path and the reflected angle on the inner surface change when performing an inspection of an axial weld on a pipe.

TP => Pipe thickness

RPart => Outer radius

βmax => Maximum probe angle

φ => Radial angle

hDefetc => Defect height

OB => The distance from the tube center to the top of the defect

Offset distance for generation of a 45º shear beam

The inspection procedure must be carried out by immersion.

d => Offset distance from the centerline.

Rpart => Outer radius.

VW => Ultrasound longitudinal velocity in water.

VT => Velocity of refracted shear beam in the test material.

TP => Material thickness.