Materials Services: Steel and Metals Services

Nondestructive Testing

GEM partners with Applied Technical Services, Inc. (ATS) to provide Nondestructive Testing (NDT) services for Special Inspections and quality control programs for structural steel and other construction materials applications. NDT is the evaluation of the quality or characteristics of a material, part, or assembly without permanently altering it or its properties.  Experienced personnel are trained and qualitied in a wide variety of test methods required by building codes, industry standards, or other specifications, and certified by one or more of the following bodies:

American Welding Society (AWS)
American Society for Nondestructive Testing (ASNT)
American Petroleum Institute (API)

NDT Services include:

    • Visual Weld Inspection – Visual weld evaluation is on the front line of quality assurance for structural steel projects, and is one of the quickest and easiest methods, as the equipment involved is minimal, and the ultimate success depends on the abilities of the certified welding inspector.  Visual weld inspections are performed on fillet weldments, which comprise approximately 80% of all industry welds.
    • Ultra Sonic Inspection – Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements used for flaw detection/evaluation, dimensional measurements, material characterization, and more.  A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy which is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. GEM utilizes a Krautkramer USM series ultrasonic portable flaw detector with a wide range of transducers for weld inspection and metal flaw detection services.
    • Magnetic Particle Testing – a non-destructive method that relies on local or complete magnetism of the component or surface being interrogated that can only be applied to Ferromagnetic parts. When a crack is present on the surface, some magnetic flux will leak out from the sides of the crack (provided that the magnetic flow is in a suitable direction relative to the crack). Small magnetic particles, if allowed to flow over the magnetized surface, can be attracted to this flux leakage.  If these particles are suitably colored, or the background is suitably colored, this concentration of particles will enhance the image of any cracks resulting in visual detection of flaws.
      Liquid Penetrant Testing – a non-destructive method used to detect surface breaking defects in any nonporous material. Liquid penetrant is applied to the surface and is drawn into defects by capillary action. Once a specified time has passed, excess penetrant is removed and a developer is applied to draw out penetrant from defects. Visual inspection is then performed.
    • Bolt Tension Evaluations – a testing method used to determine specified bolt tension via either direct tension indicators, twist off bolt, turn or the nut method, or calibrated torque wrench.  Direct tension indicators are washers that have either hollow or dye filled dimples that compress once the proper tension in the bolt is achieved.  Once the dimples have yielded a visual inspection is preformed.  Twist off bolts will shear once the proper bolt tension has been achieved.  Twist off bolts require visual inspection.  Turn of the nut method consists of tightening the bolted connection to a snug condition.  Once the bolts are snug tensioned, the washer and nut are then marked and turned a specified fraction of a turn depending on the size and length of the bolt.  Testing bolts using a calibrated torque wrench consist of obtaining a sample of three bolts, nuts, and washers and placing them in a tensioning machine (Skidmore-Wilhelm) while using a calibrated torque wrench to tension the bolts.  The recorded torque value is then averaged for each of the three bolts.

AWS Welder Qualifications

GEM/ATS provides a full range of services involved in the development of welder qualifications, and welding procedure specifications as defined by the American Welding Society.   Our team also aids in the development of in-house welding procedure manuals.  All testing and certification is performed per AWS D1.1, section 4, code requirements. These services include:

  • Welder Qualifications – Specific tests intending to determine the ability of a welder or tack welder’s ability to produce sound welds.  The specific tests identified under AWS D1.1, section 4 include visual inspection; face, root, and side bend tests; macroetch; and fillet weld break tests.  GEM offers the flexibility of performing these tests in the fabrication shop / construction site or having test specimens delivered to our laboratory for testing (depending on the specified test).
  • Welding Procedure Specifications (WPS) – Document outlining type, materials, geometries, and methods of welding.  WPS’s provided by GEM are produced in an electronic format that offers our profound knowledge, experience and professionalism easily accessible for fabricators and structural engineers.