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Choosing the Right AWS Calibration Block for Ultrasonic Testing
11th February 2025
Will Haworth, Sonatest
Selecting the correct calibration block is essential for accurate ultrasonic testing (UT) of welded structures. The American Welding Society (AWS) specifies several calibration blocks designed for various applications, ensuring precise instrument setup, flaw detection, and measurement. This guide will help you understand the most common AWS calibration blocks and their uses.
AWS calibration blocks are available in multiple materials, including carbon steel, stainless steel, aluminum, and more, depending on the inspection requirements.
1. IIW Blocks (Type 1 & Type 2)
The International Institute of Welding (IIW) Blocks are widely used reference standards for ultrasonic calibration.
Features:
- Type 1: Includes radii, drilled holes, and engraved markings for general UT calibrations.
- Type 2: Features additional radii and holes for expanded calibration options, including straight beam, phased array UT (PAUT), and surface wave applications.
Used for:
- Distance/velocity calibration
- Angle and index point verification
- Resolution and sensitivity/reference calibrations
Application:
- A general-purpose UT calibration block, especially for weld inspection.
- Type 2 offers additional references for straight beam, phased array (PAUT), and surface wave applications.
2. DSC (Distance/Sensitivity Calibration) Block
The DSC Block is a compact calibration tool designed for field use, providing multiple reference points.
Features:
- Contains radii, side-drilled holes (SDH), a notch, and engraved markings.
Used for:
- Distance/velocity calibration
- Angle and index point verification
- Sensitivity and reference calibrations
Application:
- A versatile block for quick field calibrations, particularly useful for verifying angle beam transducer performance.
3. DC (Distance Calibration) Block
The DC Block is used for calibrating time base and verifying distance measurements.
Features:
- Includes steps and radii for calibration.
Used for:
- Distance calibration for straight and angle beam transducers
- Index point verification
Application:
- Ensures accurate thickness measurements and proper beam positioning in ultrasonic inspections.
4. SC (Sensitivity Calibration) Block
The SC Block verifies sensitivity levels and angle accuracy in ultrasonic testing.
Features:
- Contains side-drilled holes (SDH) at varying depths.
Used for:
- Sensitivity calibration
- Angle verification
- Can be used for Distance Amplitude Correction (DAC) and Time Corrected Gain (TCG)
Application:
- Helps establish consistent flaw detection by ensuring sensitivity settings are properly calibrated.
5. RC (Resolution Calibration) Block
The AWS Resolution (RC) Block is used to assess an ultrasonic system’s ability to distinguish between closely spaced reflectors.
Features:
- Contains groups of holes in close proximity at varying angles.
Used for:
- Verifying resolution, particularly for angle beam applications.
Application:
- Ensures the instrument can separate multiple reflectors at different angles, improving flaw detection capabilities.
6. DS (Distance/Sensitivity) Block
The DS Block is used for verifying linearity and performing distance and velocity calibration.
Features:
- Includes 2-inch and 4-inch thickness steps.
Used for:
- Distance and velocity calibration
- Linearity checks
Application:
- A straightforward block for ensuring ultrasonic instrument gain settings are properly calibrated.
7. AWS PACS (Phased Array Calibration Standard) Block
The AWS PACS Block is specifically designed for phased array ultrasonic testing (PAUT) calibration.
Features:
- Includes radii and side-drilled holes (SDH).
Used for:
- Distance/velocity calibration
- Wedge delay calibration
- Amplitude sensitivity
- Angle Corrected Gain (ACG), Time Corrected Gain (TCG), and Distance Amplitude Correction (DAC)
- Sensitivity/reference calibration for phased array testing
Application:
- Essential for ensuring phased array UT equipment is properly calibrated, especially for beam steering and focusing.
Choosing the Right AWS Calibration Block
Each calibration block serves a specific purpose in ultrasonic testing. Here’s a quick reference guide:
- For general UT setup: Use IIW Block Type 1 for simple setups or Type 2 for more complex.
- For portable field calibrations: Use DSC Blocks.
- For verifying distance and index points: Use DC Blocks.
- For sensitivity calibration and DAC/TCG setup: Use SC Blocks.
- For resolution verification, especially with angle beams: Use RC Blocks.
- For linearity checks: Use DS Blocks.
- For phased array calibration: Use the AWS PACS Block.
By selecting the appropriate AWS calibration block, UT technicians can ensure accurate measurements, reliable flaw detection, and compliance with industry standards. Investing in the right calibration tools enhances the effectiveness and credibility of ultrasonic inspections.
For more details on AWS calibration blocks, visit our calibration-blocks page or email sales@sonatest.com.
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