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Ultrasonic testing

Ultrasonic angle beam skip distance calculator

Enter the material thickness and the refracted angle, and optionally the sound path of an indication. The calculator returns the skip distances, the leg lengths, and where the indication sits: depth, surface distance and which leg.

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Built to:ASME V Article 4AWS D1.1

Half skip surface distance

22.00mm

Full skip surface distance

43.99mm

One leg sound path

25.40mm

Full V-path

50.80mm

Indication depth

9.00mm

Indication surface distance

15.59mm · leg 1

half skip = T tan θ · leg = T / cos θ · depth in leg 1 = SP cos θ, in leg 2 = 2T - SP cos θ · surface distance = SP sin θ

Advisory result. Provisional until a qualified inspector or engineer verifies it against the governing code edition.

How it works

  1. 01Half skip surface distance = T tan θ; full skip = 2 T tan θ.
  2. 02One leg sound path = T / cos θ; the full V-path is twice that.
  3. 03For an indication at sound path SP: leg = floor(SP / leg length) + 1; depth in leg 1 = SP cos θ, in leg 2 = 2T - SP cos θ.
  4. 04Surface distance from the exit point = SP sin θ.

Formulas

Skiphalf skip = T tan θ, full skip = 2 T tan θ
Legleg = T / cos θ
Depthd = SP cos θ (leg 1), 2T - SP cos θ (leg 2)

Read before you rely on it

  • Angles are refracted angles in the test material, not wedge angles; verify on the calibration block.
  • Curved surfaces, cladding and mode conversion change the geometry; these formulas are for flat plate and thick-wall pipe.
  • Locating an indication is a screening step; sizing follows the procedure.

Answers

Questions about this calculator

What is skip distance in ultrasonic testing?

The surface distance the beam travels before returning to the scanning surface. Half skip is one bounce off the back wall, T tan θ; full skip is the return to the top surface, 2 T tan θ. It sets how far back the probe scans to cover a weld.

How do I find the depth of an indication?

Multiply the sound path by the cosine of the refracted angle. If that exceeds the thickness the beam is in the second leg and the depth is 2T minus that product.

Why 45, 60 and 70 degrees?

They are the standard shear-wave angles in steel and cover most weld geometries: 45 for thick sections, 60 general, 70 for thin material and shallow bevels.

Does intelliSPEC record the setup?

intelliNDT captures the probe, angle, calibration and indication position with the UT record, so the reader can reconstruct the scan.

See the same math on your own CMLs.

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