How to choose an ultrasonic flaw detector
By Grant, Inspection Tool Specialists. Reviewed November 2026.
Three things decide which ultrasonic flaw detector you need: the material and thickness you test, the flaws you must find and their smallest size, and the standard or procedure your work follows. If you need only wall thickness, a thickness gauge is the simpler tool; our ultrasonic thickness guide covers that choice.
Flaw detection or thickness only?
A flaw detector shows the ultrasonic echo as a waveform, so the operator can locate and size cracks, inclusions and lack of fusion in welds and castings. A thickness gauge shows only a number. Flaw detection needs training, a written procedure and reference blocks, so it suits inspection work rather than routine checks.
Which instrument?
| Need | Instrument | Typical in our range |
|---|---|---|
| Weld and casting flaw detection, entry level | Ultrasonic flaw detector | YFD300 flaw detector; TFD320 Plus |
| Flaw detection for demanding work | Ultrasonic flaw detector | MFD350B; MFD500B; MFD660C; MFD800C |
| Flaw detection with thickness and A/B-scan | Flaw detector and thickness gauge | PCE-FD 20 |
| Thickness with waveform for corroded metal | Thickness gauge with A-scan | TUM-4DL A-scan gauge |
Probes and calibration blocks
Probes decide what the detector can see. Straight-beam probes suit plate and castings; angle-beam probes suit welds. The calibration blocks set the sensitivity and the sound path, and they should match the material and geometry you test. Our range includes V1 and V2 blocks for angle-beam work, a phased array Type A block, an IOW beam profile block and a K1 block, with step and thin-wall blocks for thickness. Buy the blocks that match your procedure, not the largest set.
Procedure and records
Your procedure sets the probe, the calibration, the sensitivity and the acceptance criteria. Keep the calibration record and the data for each inspection, and check that the detector can store the scans you must report.
Price guide
As a guide to our current range, including VAT: flaw detectors from about R45,900 to R102,300; calibration blocks from about R3,000 to R25,200; probes from about R5,200. Prices change, so check the product pages and confirm the probes and blocks each quote includes.
Questions we will ask you
Tell us the material and thickness, the flaws you must find and their smallest size, the weld or part geometry, whether you need flaw detection or thickness only, the standard or procedure you work to, and the records you must keep. With that we can recommend an instrument and provide pricing.