Laboratory Witness Testing Worldwide
Independent third-party witnessing of mechanical, corrosion, hardness, chemical and rotating-equipment tests – at the mill, the manufacturer's laboratory or an accredited test house – so the results on your certificates are results you can rely on.
Role of a Third-Party Inspector in Laboratory Witness Testing
Laboratory testing proves that a material, weld or finished component actually meets the specification it was bought against. Mechanical, corrosion and chemical tests are destructive and cannot be repeated on the same piece, so who selects the specimens, who watches the test and who signs the result matters.
Many purchase orders, design codes and EN 10204 type 3.2 certificates require an independent inspector to witness the work. Qtech Control's qualified inspectors attend on your behalf anywhere in the world, verify that the laboratory follows the agreed procedure and standard, and confirm that the reported values are genuine and traceable to your order.
Hydrogen Induced Cracking (HIC) Test
Unstressed specimens are immersed for 96 hours in an H₂S-saturated solution, then sectioned and examined for internal stepwise cracking. Results are reported as crack length, thickness and sensitivity ratios (CLR, CTR, CSR) and compared with the order's acceptance limits.
Standards: NACE TM0284, API 5L Annex H, ISO 15156-2
Applications: sour-service line pipe, plate, pressure vessel steels, pipe fittings.
Sulphide Stress Cracking (SSC) Test
Specimens are loaded to a set percentage of their specified yield strength and exposed to an H₂S environment, normally for 720 hours. Any cracking or fracture is a failure. We witness specimen loading, solution preparation, H₂S purging and the final examination.
Standards: NACE TM0177 Methods A–D (tensile, bent beam, C-ring, DCB), NACE MR0175 / ISO 15156
Applications: OCTG, valve bodies and trim, wellhead equipment, bolting, welded joints for sour service.
Corrosion Testing
Accelerated tests confirm resistance to pitting, crevice and intergranular attack, or the performance of a protective coating. Typical witness points are specimen preparation, test temperature and duration, weight-loss measurement and microscopic examination of the exposed surfaces.
Standards: ASTM G48 (pitting / crevice), ASTM A262 and ISO 3651 (intergranular), ASTM A923 (duplex), ISO 9227 / ASTM B117 (salt spray)
Applications: stainless and duplex valves, heat exchanger tubes, marine components, coated steelwork.
Mechanical Testing
Tensile Testing
A machined specimen is pulled to fracture to determine yield or proof strength, tensile strength, elongation and reduction of area. We confirm specimen orientation and identity, gauge dimensions, machine calibration and the recorded stress–strain results.
Standards: ISO 6892-1, ASTM E8 / E8M, ASTM A370, ISO 4136 (transverse weld), ISO 7500-1 (machine calibration)
Applications: mill certificate verification, weld procedure qualification, forgings, castings, bolting, rail steel.
Charpy Impact Testing
A notched specimen (V notch), conditioned to the specified temperature, is broken by a swinging pendulum to measure absorbed energy in joules – a direct check of toughness and resistance to brittle fracture. We witness notch location (weld, fusion line, HAZ), temperature conditioning, transfer time and the readings for each set of three.
Standards: ISO 148-1, ASTM E23, ASTM A370, ISO 9016 (welds)
Applications: low-temperature service steels, pressure equipment, structural steelwork, weld procedure qualification.
Brinell Hardness Testing
A tungsten carbide ball, typically 10 mm under a 3000 kgf load, is pressed into the surface and the indent diameter measured. The large indent averages out coarse grain structures, making Brinell the preferred method for castings, forgings and rail, and for confirming heat treatment. A Brinell hardness test microscope is an optical measuring instrument used to measure the diameter of the circular indentation left on a metal surface after a Brinell hardness test is performed. Standards: ISO 6506-1, ASTM E10, EN 13674-1 (rail).
Applications: castings, forgings, rail and crossings, heat-treated shafts, plate and bar.
Material Composition Testing – Chemical Analysis
Qtech Control inspectors witness chemical analysis at manufacturers’ works and independent laboratories, verifying sample identification, test method and results against the purchase specification and material certificates (EN 10204 3.1/3.2).
X-Ray Fluorescence (XRF)
Laboratory XRF
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Requires a cut sample, prepared as a polished disc, pressed pellet or fused bead, so it is destructive and slower
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Usually wavelength-dispersive, operating under vacuum or helium and calibrated against certified reference materials
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Detection limits down to parts per million, with higher accuracy, better repeatability and improved light-element performance
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Used for certified analysis of many alloys and non-ferrous materials
Handheld XRF – Positive Material Identification (PMI)
The standard method for PMI of valves, flanges, piping and pressure components, typically to API RP 578.
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Non-destructive and taken to the part, giving results in seconds, so every item in a batch can be checked
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Analyses the surface at the measurement spot, typically 3–8 mm across
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Results depend on surface condition: paint, scale, plating or contamination must be removed, normally by a light local grind
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Measures the main alloying elements (Cr, Ni, Mo, Mn, Cu, Ti, Nb and others), typically within a few tenths of a percent for major elements
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Ideal for confirming grade, for example 316 rather than 304, and for detecting mixed stock
Why XRF Alone Is Not Enough for Carbon
Neither handheld nor laboratory XRF can measure carbon. Where a specification requires a low-carbon grade to be confirmed, for example 304L rather than 304, or the carbon equivalent to be checked for weldability, testing must be by spark OES, on site or in the laboratory, or by combustion analysis.
Spark Optical Emission Spectrometry (OES)
The primary method used by steel mills and foundries for certificate chemistry. A high-energy spark vaporises a small area of a ground sample, and the emitted light is analysed for each element. Fast, accurate and able to measure carbon, which is essential for weldability and carbon equivalent (CE). Mobile spark OES units are available for on-site verification.
Inductively Coupled Plasma OES (ICP-OES)
The sample is dissolved in acid and introduced into an argon plasma at 6,000–10,000 K. Highly accurate for trace and residual elements, and suitable for samples that cannot be spark-tested, such as swarf, powders and small or thin parts. ICP-MS offers greater sensitivity for ultra-trace analysis.
Combustion Analysis (Carbon & Sulphur)
The sample is burned in oxygen in an induction furnace, and the CO₂ and SO₂ released are measured, to ASTM E1019. Used where low carbon or sulphur must be confirmed, including sour-service materials to ISO 15156 / NACE MR0175, where low sulphur improves resistance to hydrogen-induced cracking (HIC).
Inert Gas Fusion (Oxygen, Nitrogen & Hydrogen)
The sample is melted in a graphite crucible under an inert gas, releasing the dissolved gases for measurement, to ASTM E1019. Hydrogen testing is critical for pipeline steels, forgings and high-strength fasteners, where excess hydrogen can cause embrittlement and cracking. Nitrogen is a deliberate alloying addition in duplex and super duplex stainless steels, contributing to strength and pitting resistance (PREN).
Rotating Equipment Testing
Speed Test (Overspeed Test)
Rotors, runners and impellers are spun above their maximum rated speed – commonly 120% for two minutes on electrical machines – to prove mechanical integrity before assembly or shipment. We witness speed measurement and hold time, plus dimensional, runout and NDT checks before and after the test.
An industrial fan speed test (RPM and performance test) measures actual rotational speed, airflow rate, static pressure, and mechanical stability against design specifications.
Standards: IEC 60034-1, API 610 / 617, client test procedure
Applications: generator and motor rotors, hydro turbine runners, compressor and pump impellers, fan wheels.
Balance Test
Rotating parts are run on a calibrated balancing machine to measure residual unbalance and confirm it is within the specified balance grade. Poor balance is a leading cause of vibration, bearing wear and premature failure. We witness the machine setup, correction weights, final readings and the residual unbalance check.
Standards: ISO 21940-11 (balance grades G2.5, G6.3 etc.), API 610 / 617 / 684
Applications: generator and turbine rotors, pump impellers, fans, couplings, spindles.
