MTU BLOCK – FULL DESCRIPTION

An MTU Block is a Magnetic Particle Testing (MT/MPI) reference block used to check the sensitivity, performance, and technique effectiveness of magnetic particle inspection systems. It verifies the ability of the technique to reveal both surface and subsurface (slightly below surface) discontinuities.

“MTU” stands for Magnetic Testing Unit.

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✔ Purpose of MTU Block

An MTU block is used to:

• Check MPI sensitivity

• Evaluate particle mobility

• Confirm field direction and strength

• Assess equipment performance (bench units, coils, yokes)

• Verify wet particle concentration

• Validate technique before inspecting actual parts

It is one of the most reliable system performance verification tools in MPI.

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✔ Construction

An MTU Block is typically:

• Made from steel (ferromagnetic material)

• Rectangular in shape

• Contains artificial defects, including:

1. Fine Surface Cracks

Located on one side for checking surface sensitivity.

2. Subsurface Cracks

Machined below the surface for checking subsurface detection ability.

3. Holes or Notches

Used to check magnetic field direction and particle flow.

4. Varying Defect Depths

Allows sensitivity comparison between different techniques or materials.

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✔ Types of MTU Blocks

MTU-V1 (Most Common)

• Contains both surface and subsurface cracks

• Cracks arranged in different orientations

MTU-V2

• Larger block with deeper and more difficult subsurface defects

MTU-V3

• Used for higher sensitivity evaluations in aerospace and critical components

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✔ How MTU Block Is Used in MPI

1. Place the block on the bench or hold under yoke.

2. Apply magnetic field (circular/longitudinal/yoke) to the block.

3. Apply wet or dry magnetic particles.

4. Observe indications on:

   • Surface cracks → evaluates surface detection

   • Subsurface cracks → evaluates penetrating ability & field strength

5. Compare visible indications with expected performance.

6. Adjust technique or equipment if required.

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✔ Applications

• Magnetic Particle Inspection (MPI/MT)

• Validation of new equipment

• Daily system performance checks

• Checking concentration of MPI bath

• Procedure and technique qualification

• Training of NDT inspectors

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✔ Advantages

• Checks both surface + subsurface sensitivity

• Reliable and repeatable

• Easy to use

• Works with bench units, yokes, coils

• Helps verify particle bath quality

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✔ Limitations

• Must be kept free from rust and scratches

• Requires proper magnetization direction

• Not a calibration device—only a performance indicator

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If you want, I can also provide:

📌 ALT image description of MTU Block
📌 Difference between MTU Block, Pie Gauge, and QQI Strip
📌 Technical datasheet format
📌 Short catalog description

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