OKOndt UDS2-77 AREMA Ultrasonic Rail Flaw Detector

OKOndt UDS2-77 AREMA Ultrasonic Rail Flaw Detector


The UDS2-77 AREMA ultrasonic flaw detector is intended for inspection of rails and switches, as well as for quick verification flaws detected by high speed test vehicles results. The detector ensures flaw detection in the entire rail cross section, excluding rail base blades. Complies with AREMA requirements and is available in two versions each with 11 channels: RSU with immersion probe unit design and SL with sliding probe unit design. Includes A-Scan, B-Scan, and A-Scan+B-Scan modes and specialized software for test result analysis and evaluation which can be viewed on the screen of the flaw detector. Designed with light-weight and shock-resistant plastic.



  • Weighs just 17 kg/37.4 lbs. (for UDS2-77 AREMA SL) and 23 kg/50.6 lbs. (for UDS2-77 AREMA RSU) due to use of light and shock-resistant plastic
  • New Flaw detector parking mode
  • Module structure: frame on rollers, central electronic unit, multiplexer units, storage battery, tank, couplant supply system, probe units, and encoder
  • All modules are easy to assemble and disassemble; they are securely attached to the flaw detector frame
  • Adjustable probe position to optimize signals
  • Adaptive rollers center the probe along the rail axis 
  • The probe suspension system ensures stable acoustic contact
  • The UDS2-77 AREMA SL can handle up to ±15° lateral inclination of the trolley
  • Continuous test results are recorded in a database format linked to distance traveled and GPS coordinates
  • Display modes: A-Scan, B-Scan, A-Scan+B-Scan
  • Test result reviewing mode on the screen of the flaw detector
  • Inspection complies with AREMA requirements

RSU and SL Probe Comparison

UDS2-77 AREMA SL Units Probe

UDS2-77 AREMA RSU Wheel Probe

A-Scan for one channel display mode

B-Scan for one channel display mode


The “Rail Inspector” program is intended for display, analysis and evaluation of test results on PC. The program includes all the necessary tools to process data. The major features of the program are:

  • Conveniently works with the database of inspected sections (stages)
  • Includes layout selection of inspection channels and selection of an inspected rail, inspected rail segment, and testing method
  • Notional size of defects measurement in B-Scan mode
  • A-Scan view based on the data recorded in B-Scan
  • Defectogram (B-Scan) view in scroll mode or in fast switch mode to the given coordinate
  • Path marking mode to mark suspicious segments of rail track while viewing test results
  • Test results can be sorted by sensitivity level from -6 to +6 dB above or below the measuring gate level
  • View and produce reports on the inspected segment mode
  • View reports on confirmatory testing mode

Technical Specifications

UDS2-77 Specifications and Comparison

Main Technical Specifications

Compliance AREMA requirements
Number of Inspection Channels (Probes) 11 psc
 Probe Type & Frequency 0°/4 MHz, ±70°, ±40/45°, ±50°SL/2 MHz
Scanning pitch 1mm at a speed of 4 km/h (2.5m/hr)
 Display Modes  A-Scan, B-Scan, A-Scan+B-Scan
 Couplant Tank Volume 5 l (1.3 gal)
 Couplant Consumption Up to 1.5 l/km (0.4 gal), at a speed of 4 km/h (2.5 m/hr)


UDS2-77 RSU and SL Comparison

Immersion probe unit design - wheel (RSU)  Sliding probe unit design (4 sliding blocks)
0°-4 MHz 0°-4 MHz
70°-2 MHz (Head Central Forward ) 70°-2 MHz (Head Central Forward)
70°-2 MHz (Head Central Backward)  70°-2 MHz (Head Central Backward)
70°-2 MHz (Head Gauge Face Forward)  70°-2 MHz (Head Gauge Face Forward)
70°-2 MHz (Head Gauge Face Backward)  70°-2 MHz (Head Gauge Face Backward)
70°-2 MHz (Head Field Face Forward)  70°-2 MHz (Head Field Face Forward)
70°-2 MHz (Head Field Face Backward)  70°-2 MHz (Head Field Face Backward)
2 x 40°- 2 MHz (Web, Foot Forward / Backward) 2 x 45°- 2 MHz (Web, Foot Forward / Backward)
2 x 50°- 2 MHz (Head Side Looking)  2 x 50°- 2 MHz (Head Side Looking)
Specifics of Application/Tester Comparison
Limited to soft tire bumps  Limited to rail level differences of no more than 15 mm (0.6") at rail junctions
Requires a strictly vertical position of trolley
during rail testing
Trolley tilt of +/- 15º is acceptable during rail
Comparison of Costs, Repair and Maintenance
The cost of repair/replacement of the probe
unit (RSU) is higher
The cost of repair/replacement of sliding
probe units is lower
The cost of soft tire replacement is lower The cost of sliding probe units replacement is higher
The process of soft tire replacement is more
The process of sliding probes replacement is
Flaw Detector: Higher Cost Flaw Detector: Lower Cost
Net Weight (Without Liquid)
23 kg (50.7 lbs.) 17 kg (37.5 lbs.)
Description Part # Saved Price Select Option Add to
OKOndt UDS2-77 AREMA Compliant Ultrasonic Single Rail Flaw Detector, SL and RSU Models UT-OKO-UDS2-77-AREMA Request Pricing