How to read nondestructive examination callouts per AWS A2.4:2020 Clause 17. Covers all six primary NDE methods, arrow-side vs other-side placement, the volumetric vs surface distinction, examination combinations, and D1.1:2025 inspection cross-references.
NDE Symbol Anatomy — A2.4 Figure 17.1
Key distinction: NDE symbols look like welding symbols (reference line + arrow) but carry letter designations instead of weld type graphics. The letter placement relative to the reference line follows the same convention: below = arrow side, above = other side, centered = no side preference.
Examination Methods — Table A6
Six Primary NDE Methods
AWS A2.4:2020 Table A6 defines letter designations for each NDE method. They fall into two categories that determine how the symbol is placed on the reference line:
Code
Method
Category
Side Significance
RT
Radiographic Testing
Volumetric
Typically centered (no side preference)
UT
Ultrasonic Testing
Volumetric
Typically centered (no side preference)
MT
Magnetic Particle Testing
Surface
Has side significance (arrow/other)
PT
Penetrant Testing
Surface
Has side significance (arrow/other)
VT
Visual Testing
Surface
Has side significance (arrow/other)
ET
Eddy Current Testing
Surface
Has side significance (arrow/other)
Volumetric vs surface: Volumetric methods (RT, UT) examine the full cross-section of the weld. The examination penetrates through the entire thickness, so the side of approach typically does not affect the result. Per §17.5.5, the letter is centered on the reference line. Surface methods (MT, PT, VT, ET) examine the surface and near-surface region only. The side you examine from matters, so the letter placement follows the arrow-side / other-side convention per §17.5.2 and §17.5.3.
Individual Methods
NDE Method Symbol Pages
Each method page covers: symbol placement, practical applications, D1.1 requirements, and CWI exam tips.
Placement Rules — Arrow Side, Other Side, Both Sides
Arrow side (§17.5.2): Place the letter designation below the reference line. The examination is performed on the side of the part that the arrow points to.
Other side (§17.5.3): Place the letter designation above the reference line. The examination is performed on the side opposite to where the arrow points.
Both sides (§17.5.4): Place the letter designation on both sides of the reference line. The same or different methods can be specified for each side.
Centered (§17.5.5): When the designation has no arrow- or other-side significance, or there is no preference from which side the examination is to be made, the letter is centered on the reference line. This is typical for volumetric methods (RT, UT).
Placement Examples — A2.4 Figure 17.3
A2.4 §17.5.6 & §17.7
Combining NDE Methods and Welding Symbols
Multiple NDE methods on the same side are separated by a plus sign. For example, VT+MT below the reference line means perform both visual and magnetic particle testing on the arrow side.
NDE symbols can be combined with welding symbols on the same or multiple reference lines (§17.7). When using multiple reference lines, the first operation is specified on the line nearest the arrow. A typical callout shows the welding symbol on the first reference line and the NDE symbol on the second — meaning: first make the weld, then inspect it.
The examine-all-around supplementary symbol (circle at the arrow junction) and the field examination flag work exactly like their welding symbol counterparts (§17.9).
CWI Exam Tip: The volumetric vs surface distinction is one of the most commonly tested NDE symbol concepts on the CWI Part A exam. Remember: RT and UT penetrate through the full thickness (centered on reference line), while MT, PT, VT, and ET are surface or near-surface methods (arrow/other side placement).
Common Questions
NDE Symbol FAQ
What are NDE symbols on a welding drawing?
NDE symbols are standardized notations placed on engineering drawings to specify which nondestructive examination methods must be applied to a weld or part. They are defined in AWS A2.4:2020 Clause 17. Like welding symbols, NDE symbols use a reference line and arrow, but instead of a weld type graphic, they display letter designations for the examination method: RT for radiographic testing, UT for ultrasonic testing, MT for magnetic particle testing, PT for penetrant testing, VT for visual testing, and ET for eddy current testing. The letter placement relative to the reference line indicates which side of the part to examine. NDE symbols can be combined with welding symbols on the same reference line to specify both the weld and the required inspection in one callout.
What is the difference between volumetric and surface NDE methods?
Volumetric methods (RT and UT) examine the full cross-section of a weld or part. Because they penetrate through the entire thickness, the side of approach typically does not affect the examination result. Per AWS A2.4:2020 section 17.5.5, when there is no preference from which side the examination is to be made, the letter designation is centered on the reference line. Surface methods (MT, PT, VT, and ET) examine the surface and near-surface region only. Because the examination result depends on which surface is inspected, these methods typically have arrow-side or other-side significance, with the letter placed below or above the reference line per sections 17.5.2 and 17.5.3. This distinction is one of the most commonly tested concepts on the CWI Part A exam.
Can NDE symbols be combined with welding symbols?
Yes. Per AWS A2.4:2020 section 17.7, symbols for nondestructive examination and welding symbols may be combined on the same reference line. The welding symbol specifies the weld type and dimensions, while the NDE symbol specifies the required inspection. When multiple reference lines are used, the sequence of operations is specified from the reference line nearest the arrow (first operation) outward. For example, a drawing might show a CJP groove weld symbol on the first reference line and an RT examination on the second reference line, meaning: first make the groove weld, then perform radiographic testing.
How do you specify NDE on both sides of a joint?
Per AWS A2.4:2020 section 17.5.4, examinations to be made on both sides of the part are specified by placing the examination method letter designation on both sides of the reference line. For example, MT above and MT below the reference line means perform magnetic particle testing on both the arrow side and the other side. When two different methods are required on different sides, different letter designations appear on each side, such as VT below (arrow side visual) and PT above (other side penetrant). When multiple methods are required on the same side, they are separated by a plus sign, such as VT+MT below the reference line.
What NDE does D1.1 require for CJP groove welds?
D1.1:2025 Clause 8 specifies NDE requirements based on connection type and loading. For statically loaded structures, CJP groove welds in tension splices and connections may require RT or UT as specified in the contract documents per Clause 8.15. For cyclically loaded structures, all CJP groove welds may require RT or UT as specified in the contract documents per Clause 8.15, plus VT per Clause 8.9. MT or PT may be required at intermediate stages for backgouged joints. The specific NDE requirements depend on the joint category (tension, compression, shear), the structure type (static vs cyclic), and whether the joint is a demand-critical connection. The drawing callout uses NDE symbols per A2.4 Clause 17 to communicate these requirements to the inspector.