Thursday 30 August 2012

Portable NDT instruments

Expanding its non-destructive testing (NDT) techniques and complementing its existing array of advanced instruments, Keighley Laboratories has invested in a portable conductivity meter, which measures the electrical conductivity of non-ferrous metals employing the eddy current method, and a pocket instrument for convenient and fast coating thickness measurement, using magnetic induction and eddy current technologies. Both measuring techniques are applicable to the aerospace, automotive, petrochemical, engineering, heat treatment and other fields and complement the specialist NDT services the company already offers to industry clients.

Through its Technical Services division, Keighley Labs covers many of the mainstream NDT methods, notably magnetic particle crack detection, dye penetrant testing, ultrasonic flaw detection, magnetic permeability, positive material identification, residual magnetism and ferrite determination, as well as radiography on a sub-contract basis. Its highly skilled and experienced NDT technicians are qualified to at least PCN Level 2 in several disciplines and are able to define and implement tests that detect and analyse material flaws that might otherwise give rise to critical component failure or quality control issues, either working in the laboratory or at the customer site. Many methods are covered by the company’s UKAS accreditation, for testing at customer premises.

The electrical conductivity of a metal depends on various factors, such as chemical composition, the stress state of its microstructure and mechanical properties, so can be used for sorting metals and checking proper heat treatment, as well as identifying how well a metal conducts electrical current for anodising and other processes. The company’s new instrument will measure the electrical conductivity of non-ferrous metals, such as aluminium alloys, copper and even stainless steels, using the eddy current method in accordance with DIN EN 2004-1 and ASTM E 1004 standards and determining conductivity of materials under paint or synthetic coatings up to 500µm thick.

Employed both in-house and for external clients, it will enable Keighley Labs to monitor the hardness and strength of heat treated materials like aluminium alloys and inspect for any heat damage. The same instrument will also be used for scrap metal sorting at customer sites, determining the purity of non-ferrous metals and verifying the homogeneity of alloys, as well as for the inspection of finished goods. It will even detect counterfeit coins.

The other NDT technique, for measuring the precise thickness of such applied coatings as paint, powder coatings, plastics and plated finishes, is equally important for ensuring compliance with thickness specifications, preventing defective coatings and subsequent corrosion, maintaining product quality and controlling production costs. The company’s newly-acquired pocket instrument will provide for non-destructive measurement of the total thickness of coatings up to 2000µm thick, applied to ferrous and non-ferrous materials. It will automatically recognise the underlying material, such as steel or aluminium, and select the appropriate one of two test methods, which are eddy current and magnetic induction in accordance with ISO 2178, ASTM D7091 and ISO 2300 standards.

With an on-board memory for up to 1000 readings, it will allow Keighley Labs technicians to measure paint, lacquer or plastic coatings on a whole range of metals, anodised coatings on aluminium components, electro-plated zinc, chromium and copper finishes, and sputtered thin-film deposition.

As with all advanced NDT techniques, a considerable degree of operator skill and experience is required to apply these test methods properly, obtain the maximum amount of information, then interpret the results and provide feedback for the client. With the newly-acquired instruments, this process will be aided by the capacity to download results directly from the portable devices to the NDT department’s computers, for error-free data transfer and subsequent analysis and report generation.

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