When inspecting tubing with a diameter smaller than the transducer, which device is used to confine the sound beam to the proper range of angles?

• A. A scrubber
• B. A collimator
• C. An angle plane angulator
• D. A jet stream unit

Answer: (B)

When the item being inspected is smaller than the transducer, you need to shape and limit how the ultrasound energy travels so it stays within the intended region of the tube rather than spreading everywhere. A collimator does exactly that: it confines the sound beam to a narrow, defined angular range by providing apertures or channels that block off-axis paths. This keeps the beam directed along the desired paths and makes the reflections from the tube walls easier to interpret, improving sensitivity and accuracy for flaw detection in small-diameter tubing.

The other devices aren’t designed to constrain the beam in the same way. An angle plane angulator adjusts the beam’s orientation but doesn’t limit its spread. The scrubber and jet stream unit aren’t about shaping or steering the ultrasonic beam. So the collimator is the appropriate choice.