How to Interpret B-Scan vs. C-Scan Ultrasonic Data

Home NDT How to Interpret B-Scan vs. C-Scan Ultrasonic Data

Ultrasonic Testing (UT) is a cornerstone of non-destructive testing (NDT), but understanding the output visuals can be challenging if you’re not familiar with how B-scan and C-scan data work. Both formats offer critical insights—but they serve different purposes.

In this guide, we’ll break down the key differences between B-scan and C-scan displays, how to interpret each, and when to use them in the field.

What Is a B-Scan?

A B-scan (or “brightness scan”) is a cross-sectional view of the material being inspected. Think of it like a side profile or “slice” through a tank wall or pipe.

X-axis: Scan path or position along the surface
Y-axis: Thickness or depth
Color/Grayscale: Echo signal strength or amplitude

How to Read It:

The top of the image is usually the front surface of the material.
The bottom line (back wall) represents the total thickness.
Any discontinuity—like a crack or thinning wall—will show up as a mid-wall indication or irregular contour.

When to Use It:

For tank floor or vertical wall thickness profiling
When you need a side view of the material’s integrity
For generating real-time feedback during manual inspections

Pro tip: B-scan is best for measuring thickness and visualizing metal loss in a straight line or scan pass. It’s ideal for mapping corrosion across weld seams or shell courses.

What Is a C-Scan?

A C-scan offers a top-down view of the area under inspection, like looking at a heat map from above.

X-axis / Y-axis: Physical layout of the scan area
Color coding: Corresponds to remaining wall thickness or defect amplitude

How to Read It:

Each color block or pixel represents a single data point from the scan grid.
The colors indicate varying material thickness—often in real-time using software like Analyst™ XR.
Areas of concern (corrosion, thinning) will appear in hot colors like red or orange.

When to Use It:

For full-area corrosion mapping on tanks, vessels, or large-diameter pipe
To detect trends and deterioration patterns
For visual reporting and archiving using code-driven tools like API 653 or ASME B31G

Pro tip: C-scan offers the big picture, making it ideal for spotting high-risk zones or tracking degradation over time. It’s also perfect for use with ScanTech’s XR and Vertex scanners equipped with Analyst™ XR software.

B-Scan vs. C-Scan: Key Differences

Feature	B-Scan	C-Scan
View Type	Cross-sectional (side view)	Planar (top-down view)
Best For	Thickness profiling	Full-area corrosion mapping
Resolution	Medium	High (grid-based)
Data Output	Line scan	2D map
Use Case Example	Tank wall welds	Tank floors and pipe elbows

Why It Matters for Field Work

Choosing the right scan type can make or break an inspection. For example:

If you’re doing a quick check on wall loss? → Use B-scan.
Need to assess full corrosion zones and report for compliance? → Use C-scan.

Each delivers actionable data—but only when used in the right context with the right tools.

Final Thoughts: Precision Drives Decisions

Understanding the difference between B-scan and C-scan isn’t just academic. It’s essential for getting accurate, repeatable, and compliance-ready results in ultrasonic testing.

Whether you’re mapping wall loss in a paper dryer or verifying corrosion in a petrochemical tank, interpreting the scan correctly means safer assets and smarter calls in the field.