Radiographic Inspection

Goodwin's manufacturing facility is supported by comprehensive in-house radiography facilities able to fully inspect heavy and large section castings and fabrications.

The photo shows a 7,000kg valve body castings undergoing 100% radiography on the 8.5MeV linear accelerator. The linear accelerator provides a powerful output with a small source size. This enables a 150mm thick section to be radiographed in 1 minute (compared to 60 minutes with a Co60 isotope source).

Supporting the linear accelerator is a comprehensive film development room and viewing facility with the full range of ASTM reference radiographs (E446, E186, E280).

Radiographic Inspection Principles

Radiography (RT) involves the use of penetrating gamma- or X-radiation to examine a casting to show defects and internal features.

An X-ray machine (Linear Accelerator) or radioactive isotope is used as a source of radiation. Radiation is directed through the casting and onto film which is then developed. The resulting radiograph shows the internal features and soundness of the part.

Material thickness and density changes are indicated as lighter or darker areas on the film. The darker areas in the radiograph represents internal voids or thickness changes.

Ultrasonic Inspection

The photograph shows the ultrasonic examination of a structural roof node. Ultrasonic inspection is used for volumetric examination. Angle probe examination is very sensitive when scanning welds and angle features on a casting.

Goodwin use Krautkrammer, Sonatest and Staveley ultrasonic sets, both conventional (CRT) and digital units. Fully qualified PCN and SNT level 2 casting inspection operators are employed under the supervision of level 3 personnel.

A full range of calibration blocks (including ASTM A609) are available.

Ultrasonic Inspection Principles

In ultrasonic testing (UT), high-frequency sound waves are transmitted into a material to detect imperfections or to locate changes in wall thicknesses.

The most commonly used ultrasonic testing technique is pulse echo, whereby sound is introduced into a test object with an ultrasonic probe. The reflections (echoes) from internal imperfections or the part's geometrical surfaces are returned to a receiver and displayed on a CRT screen or digital display.

Magnetic Particle Inspection

The photograph shows a 4,500kg alloy steel crankshaft undergoing magnetic particle inspection using an 8,000 amp heavy-cycle, programmable unit.

Magnetic particle inspection detects surface defects on magnetic materials. Either the contrast or fluorescent method is used.

Magnetic Particle Inspection Principles

Magnetic Particle (MT) inspection method is used for surface inspection. It is carried out by inducing a magnetic field in a ferromagnetic material and then coating the surface with iron particles (either dry or suspended in liquid).

Surface and near-surface flaws produce magnetic poles or distort the magnetic field in such a way that the iron particles are attracted and concentrated. This produces a visible indication of defect on the surface of the material.

Liquid Penetrant Inspection

Goodwin use water washable and solvent removable penetrant inspection for surface inspection of non-magnetic castings such as stainless steels and nickel alloys.

In the photograph is a stainless steel check valve undergoing water washable penetrant inspection.

Penetrant Inspection Principles

The test object is coated with a solution that contains a visible or fluorescent dye. Excess solution is then removed from the surface of the object but leaving it in surface breaking defects. A developer is then applied to draw the penetrant out of the defects.

With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen . With visible dyes, vivid colour contrasts between the penetrant and developer make "bleedout" easy to see.