Limitations

PS 1000 X-Scan Limitations
Due to the scanning principle employed, certain unfavourable circumstances may affect the result:

  • Multiple layers and very inhomogeneous composition of walls or floors. Objects that lie at an angle in the wall.
  • Metal surfaces and damp areas; under certain circumstances, these may be detected as objects in the material bring scanned. The concrete must have dried out fully (at least 4 weeks, depending on the weather, air humidity and temperature).
  • Cavities or voids in the material scanned; these may be detected as objects.
  • Proximity to appliances that emit powerful magnetic or electromagnetic fields, such as mobile phone relay stations or electric generators.
  • Under certain circumstances, objects in a 2nd layer may be difficult to locate. Steeply inclined objects or those lying at a 45° angle to the scanning direction are also difficult to detect.
  • Objects lying perpendicular to the surface scanned cannot be detected correctly.
  • The type or class of material detected or the thickness / diameter of objects found cannot be indicated.
  • Empty plastic pipes / conduits lying alongside steel reinforcing bars cannot always be reliably located as a minimum distance of 40mm (1.6 in) between objects is necessary.
  • Scanning performance limitations must be expected in fibre-reinforced concrete and where layers of insulation, tiles or coatings etc. are present.
  • Objects positioned at greater depth beneath a layer of reinforcing mesh can be detected reliably only if the mesh width is at least approx. 13cm (5.1 in).
  • Objects positioned close to the rear surface of a slab can be located only approximately (or not at all). For reliable detection, objects must be positioned no closer than approx. 40mm (1.6 in) to the rear surface of the slab.
  • Very closely-meshed reinforcing mesh may cause signal interference that looks like objects in the image displayed.
  • Water-filled pipes may appear on the screen as 2 objects, one on top of the other.
  • Over-detection and multiple reflections; Amplification in the signal processing stage is set up in a way that tends to cause too much, rather than too little, to be displayed. Another effect of this is that multiple reflections may appear as objects. Very similar “duplicate” objects then appear behind the real objects in the upper layer.
  • Multiple reflections from the rear surface may result in “ghost objects” that seem to appear behind the slab.
  • Objects positioned behind other metal or metallic objects (foil, sheet metal, etc.) cannot be detected
  • Maximum depth of detection may be reduced by concrete with high signal absorption properties.
  • The detection performance stated in specifications is for concrete of the B35 grade with 16mm (0.6 in) aggregates. Larger aggregate sizes reduce detection performance. Reduced detection performance is also to be expected on the underside of horizontal slabs due to the higher concentration of aggregates present in the concrete in this area.
  • Plates or other wide or extensive objects with a length of more than 20 cm (7.9in) may be detected incorrectly. It is possible that only the edges of the plate are shown in the image.
  • Undesired magnetic fields (such as in the proximity of transformers, motors and other equipment or devices that generate powerful stray magnetic fields may have a decisively negative effect on the detection performance of the EM sensor. In such cases, the results of the scan may be incorrect.

PS 200 Limitations
Reliable Measurements
Base Material

  • Reinforced concrete.
  • Reinforced CMU.
  • (Brick)

Detected Objects
Rebars which comply with one of the following standards:

  • DIN 488
  • ASTM A615/A 615/M-01b
  • CAN/CSA-G30. 18-M92
  • JIS G 3112
  • GB 50012-2002 (China)
  • Metal conduit if sufficient spacing from rebars.

Environment / Working conditions
Smooth and flat surfaces.
Rebar layout Direction

  • Rebars lying orthogonal or within ±5° of 90° to scanning direction.
  • Reinforcement running parallel to the surface.

Rebar layout Diameter

  • Neighbouring bars with a similar diameter.
  • Standard diameters in between 6 – 36mm up to a depth of 60mm, if s:c ≥ 2:1.
  • Calibrated bar sizes: {6,8,10,12,14,16,20,25,28,30,36}
  • Device is calibrated to be accurate to within ± 1 of the above intervals, however this is strongly affected by environmental conditions.

Rebar layout Spacing

  • Minimum bar spacing either 36mm (1.4 in) OR Minimum ratio of spacing : coverage (s:c), whichever value is greater.
  • Minimum ratio of spacing : coverage
  • Depth calculation / bar diameter estimation s:c = min 2:1
  • Bar location s:c = min 1.5:1

Rebar layout Depth calculation

  • Neighbouring bars at similar depth / size.
  • For accurate depths readings minimum depth of 20mm (0.8 in). For readings at all min. 10mm.
  • Maximum depth determination differs with rebar diameter.
  • Typically if diameter is known (DIN) Image Scan / Block Scan:
  • ≤ 10mm: up to 100mm
  • ≤ 14mm: up to 120mm
  • ≤30mm: up to 140mm
  • 36mm: up to 160mm

Linear Scan: up to 100mm

  • Accuracy for unknown bar diameter: ± 10% for depths greater than 20mm.

Pile Integrity Test Limitations

PIT is standardised by ASTM D5882 Standard Test Method for Low Strain

Integrity Testing of Deep Foundations

 Limitations


1. Pile Integrity Test does not provide any information on the load bearing capacity of piles and deep foundations.
2. Pile Integrity Testing cannot be conducted over pile caps or any other attached structure.
3. Pile Integrity testing of cross sections below a major crack (that crosses the entire cross-sectional area) is not possible.
4. This test is not effective in piles with highly variable cross sections
5. Pile integrity is generally not suitable for testing steel sheets, H-section, or unfilled pipe piles.
6. When the toe reflection is not evident, integrity evaluation may not be conclusive.
7. In some cases, it is difficult to distinguish the soil response, and the (pile) toe response.
8. Pile Integrity testing identifies changes in the impedance of a pile, which is determined by the pile’s area, elastic modulus and density. Which of these factors has changed cannot be isolated. Any change in impedance will be interpreted as change in area.
9. If it is not possible to determine the wave speed in a single pile, the average value from neighboring piles may be used however accuracy will be decreased.
10. The pile length/diameter ratio must be between 10 and 30. The engineer may decide to test piles outside this ratio. The probability of obtaining suitable results will decrease.

What may be detected with PIT:
• Pile toe
• Lage inclusion
• Crack through parts or the whole of the pile
• Joint (e.g. from different pour stages)
• Increase in cross-section
• Decrease in cross-section
• Soil layer change
• Major material changes

What probably may not be detected with PIT:
• Gradually increasing diameter
• Gradually decreasing diameter
• Curved pile
• Gradual material changes
• Small inclusions
• Local loss of cover
• Debris at toe

ULTRASONIC LIMITATIONS

1. Maximum depth of inspection in concrete = 2500 mm
2. Maximum view depth in marble and granite = 2000 mm
3. Maximum view depth in reinforcement concrete = 800mm
4. Guaranteed Minimum and Maximum Measurable Thickness in concrete = 50 – 600 mm
5. Minimal size of detected reflector = sphere with a diameter of 30 mm at a depth of 400 mm in concrete grade M400
6. Limits of permissible absolute measurement accuracy of the thickness, where Х – thickness being measured = ±(0.05∙Х+10) mm
7. Measurement range of the depth of the flaw location (a sphere 20 mm in diameter at least and 200 mm in length at least) = from 50 to 400 mm
8. Limits of permissible absolute measurement accuracy of the depth of the flaw location, where Н – depth being measured = ±(0.05∙Н+10) mm

Due to the scanning and technology principle employed, certain unfavourable circumstances may affect the result:
• Multiple layers of reinforcing, obstructions or materials and very inhomogeneous material composition. Objects that lie at an angle in the wall
• Objects behind cavities or voids cannot be detected
• Proximity to appliances that emit powerful magnetic or electromagnetic fields, such as but not limited to; mobile phone relay stations or electric generators.
• Very closely spaced reinforcing or objects may cause signal interference