SELECTION OF PROBE ANGLE:
There are three methods for selecting a probe angle, these are:
Based on groove angle:
Probe Angle (Ø) = 90 – α/2
Where, α – Groove angle and Ø- Probe Angle
As per AWS:
- 0 – 30 mm Thickness – 700 Probe
- 30 – 40 mm Thickness – 600 Probe
- > 40 mm Thickness – 450 Probe
As per approved procedure:
Third way of selection of Probe angle is as per the procedure approved by any competent person/client.
SKIP DISTANCE AND BEAM PATH (SOUND PATH) CALCULATION:
Skip distance calculation:
(Abbreviations: HSD – Half Skip Distance, FSD – Full Skip Distance)
Tan Ø = Perpendicular (BG)/ Base (AG) = AC (or HSD)/THK
Hence, Tan Ø = HSD/T
Or, HSD = T X Tan Ø
Similarly, FSD = 2T X Tan Ø
And, 1-1/2 Skip Distance = 3T X Tan Ø
Beam Path calculation:
(Abbreviations: HBP – Half Beam Path, FBP – Full Beam Path)
Cos Ø = Base (AG) / Hypotenuse (AB) = THK/HBP
Or, HBP = T / Cos Ø
Similarly, FBP = 2T / Cos Ø
And, 1-1/2 Beam Path = 3T / Cos Ø
NOTE: 1. Scanning area should be 1-1/2 Skip Distance i.e. 3T X Tan Ø
2. Probe Travel Speed shall not be more than 150 mm/S
Read more: How to write a Welding Procedure Specification (WPS)
Read more: Welding Positions
Read more: Preheating – How, When and Why
Read more: Welder Qualification test
Read more: Thickness range as per ASME Section IX