NTS Ultrasonics
NTS Ultrasonics Pty Ltd

Ultrasonic wheel probes

NTS Ultrasonics builds ultrasonic wheel probes, also known as "roller search units" or RSUs. These wheels can be used with ultrasonic NDT systems for applications such as corrosion mapping and ultrasonic flaw detection. The wheel probes are usually supplied as an assembly with a caliper, or support bracket, that can be used for mounting the wheel probe.

NTS ultrasonics offers two basic wheel probe designs: the RL70 and the PL180. These wheel probes can be customized. The internal transducer mountings can be altered to support different numbers of transducers and different beam angles. Larger diameter wheel probes can be modified to accept single or multiple phased array transducers. The calipers can be simple brackets or modified with suspension and couplant feeds.

RL70 ultrasonic wheel probes

The RL-70 is a small diameter ultrasonic wheel probe with a long internal water path for it's size. It is a single transducer wheel suitable for thickness testing, corrosion mapping and similar applications.
The PL-180. A 180 mm diameter wheel probe is intended for heavy duty use with multiple transducers. It is suitable for rail flaw detection and steel mill applications. This wheel probe can be modified to accept phased array transducers.
70 mm diameter (approx.)
70 mm internal water path (allows inspection to approximately 275 mm in steel)
Suitable for general ultrasonic inspection applications
• thickness testing
• corrosion mapping
• flaw detection
Accepts single 16 mm immersion style transducer
Tyre material (black) with an acoustic impedance close to that of water
Stainless steel construction
180 mm diameter (approx.)  when filled
Internal water paths in excess of 100 mm possible
Can accept multiple transducers, e.g. 0 degree. 40 degree, and 70 degree as used in rail flaw detection
Wide enough to accept paintbrush style transducers or phased array transducers
Transducers are electrically isolated from metal parts of the wheel
Uses a tough polyurethane tyre with low sidewalls to prevent the tyre from being pulled out of the rim
Easily customized
RL-70 Accessories:
Filling tube
Caliper or hand roller
RL-70 Downloads (pdf):
RL-70 information
RL-70 outline drawing
PL-180 Accessories:
Caliper for holding the wheel probe
Seal making system
Filling pump
PL-180 Downloads (pdf):
PL-180 information
PL-180 outline drawing
Material   Attenuation dB/mm Hardness
@ 1 MHz @ 2.25 MHz @ 5 MHz Shore A
Rubber 1.6 2.0 2.4 40-50
Polyurethane 1.2 1.43 3.4 90-95

Properties of wheel probe tyre materials
ultrasonic roller search unit for phased array transducer
PL-180 modified to accept multiple phased array transducers
Probe Assemblies >> Ultrasonic Wheel Probes
 
Home || Ultrasonic NDT || Probe Assemblies || High Power Ultrasonics || Consulting and Design || About
Filling an RL70 ultrasonic wheel probe
Video: Filling an RL70 ultrasonic wheel probe
Click on the YouTube icon to open in a new tab.
Home || Ultrasonic NDT || Probe Assemblies || High Power Ultrasonics || Consulting and Design || About
NTS Ultrasonics Pty Ltd, Perth, Western Australia,  Tel: +61 8 9367 1578, Email: ntsu@ntsu.net.au

PL180 ultrasonic wheel probes

 
The standard PL180 ultrasonic wheel probe is suitable for use in ultrasonic rail flaw detection and similar applications. The standrad probe configuration produces 0, 40, and 70 degree beams in steel. The preferred configuration is for the 40 and 70 degree forward facing beams to be produced in one wheel probe, and the 40 and 70 degree backward facing beams produced in a second (assymteric configuration). This minimizes the possiblity of strong reflections being produced internally in the wheel which may interfere with echoes produced in the rail, as occurs with the symmetric configuration. However, the assymetric configuration requires two wheel probes per rail, whereas the symmtric configuration needs only one, and is favoured by some, for walking stick applications.
Assymetric transducer configuration (preferred)
transducer arrangement in ultrasonic wheel probe
Symmetric transducer configuration
transducer arrangement in roller search unit
NTS Ultrasonics Pty Ltd
RL70 roller search unit with wheel probe and caliper with suspension
ultrasonioc roller search unit
Standard PL-180 wheel probe with caliper
heavy duty ultrasonic roller search unit
Sitemap
~ Ultrasonic Wheel Probes
When wheel probes contain transducers at angles intended to produce refracted beam angles in the test item, it is necessary to make sure that the fluid used to fill the wheel has minimal variation of ultrasonic velocity with temperature. So, for a wheel intended for use in ultrasonic rail flaw detection, it is necessary to make sure that the refracted 40 degree and 70 degree beams are actually as close as possible to the nominal angles over the working temperature range. Water has a significant positive temperature coefficient of ultrasonic velocity. Over a temperature range of 10 degrees C to 40 degrees C, a nominal refracted angle in steel of 70 degrees can actually vary from 75 to 66 degrees. Most liquids have a negative temperature coefficient of ultrasonic velocity, and certain fluids, when mixed with water, can create a mixture with minimal variation of ultrasonic velocity with temperature. NTS Ultrasonics recommends a particular fluid mixture that users can mix themselves using readily available components.
graph: temperature variation of the ultrasonic velocity of wheel probe fluid
The graph above shows the variations of ultrasonic velocity with temperature for water and the wheel probe fluid mixture recommended by NTS Ultrasonics. The graph below shows the resulting errors in a nominal 70 degree angle refracted shear wave from temperature variations of the NTS Ultrasonics fluid mixture, and water.
graph: refracted angle errors with temperature variation in ultrasonic wheel probes

Customizing

Transducer configurations for railway inspections

Wheel probe filling fluid

The standard PL180 wheel probe uses a machined plastic transducer holder. Users can be supplied with mounting details for the holder and machine new holders for their own transducer configurations. The transducer holder system also allows users to fit side looker transducers.
The standard PL180 wheel probe uses a machined plastic transducer holder. Users can be supplied with mounting details for the holder and machine new holders for their own transducer configurations. The transducer holder system also allows users to fit side looker transducers.
Simple calibration rig for PL180 wheel probe

Calibration

PL180 wheel probes are calibrated in a similar way to conventional manual transducers using an IIW calibration test block in a special test rig. The index points for the various transducers in the wheel and refracted angles in steel are recorded. Any adjustments required are made during the calibration process. Old fashioned "zeroing" is not required, as this favours the less critical 0 degree probe over the more critical 40 degree shear wave probe.
roller search unit calibration
Download "An introduction to ultrasonic wheel probes" (pdf)