The Belgian manufacturer SwitchGear Company (SGC) has installed an X-ray Computed Tomography (CT) system to shorten product development times and maintain high-quality standards for components delivered by suppliers.

The Microfocus system from Nikon Metrology (www.nikonmetrology.com) is rated at 225kV and is installed on the production floor, where it is used to non-destructively inspect the quality of components used in SGC’s medium-voltage cubicles and the integrity of welded enclosures filled with SF6 (sulphur hexafluoride — an inert gas used as an insulating medium in electrical systems).

With a history dating back over 35 years, SGC focuses on the design and production of medium-voltage switchgear from 3kV to 36kV, suitable for both indoor and outdoor use. The cubicles can be compared to switchboards for domestic applications but operate at much higher voltages and currents. They have a wide application range and are used in electrical distribution centres, transformer stations, wind turbines and production plants, for example.

Patrick De Clercq, technical project manager at SGC, says: “Our products are made to a high standard and have a life of more than 30 years. In order to guarantee this lifespan, product quality needs to be 100% under control.”


The copper connectors for high-power cables are sealed in an isolating epoxy and housed in a pressurised SF6-filled enclosure. Porosity or air inclusions in the epoxy need to be avoided at all costs, as they can cause internal arcs that can result in explosions and permanent damage to the equipment.

One of the critical elements here is the high-quality welding of the enclosures around the connectors to avoid SF6 leaks. The quality control of these components and processes, especially of the welded joints, is a crucial step in the production process.

Destructive testing

Until recently, SGC used destructive test methods to inspect these epoxy-clad components for internal imperfections and to verify the perfect fit of the copper tube to the resin, which necessitated the part under test being sliced. This was time-consuming; it was also difficult to draw the right conclusions as to whether the imperfections were caused by the destructive tests or were already present due to the production process. To gain better insight into the quality of the epoxy, non-destructive X-ray inspection was considered the best option.

Before deciding to invest in X-ray equipment, SGC performed several benchmark tests with different X-ray/CT manufacturers. As the CT images of Nikon Metrology revealed what SGC expected to see in the components, a decision was easy to make.

“We were immediately impressed with the X-ray results. The fact that Nikon Metrology also offered a 225kV source while other vendors offered a 180kV system was an important additional benefit provided by the Nikon Metrology XT H 225 ST system,” said Mr De Clercq.

By applying a higher voltage, users can penetrate thicker or higher-density materials. The 225kV source can easily penetrate 12cm of epoxy. For metal parts, an even higher voltage can be necessary to irradiate the metals (for very specific X-ray scans, it is possible to use the 450 or 750kV systems that Nikon Metrol-ogy has available in its technical demonstration centre).

The recently installed system is also used to inspect the quality of products delivered to SGC from external suppliers. For parts in series production, X-rays are used to verify quality by testing samples from the batch (as SGC has ISO 9001:2008 certification, it is important to constantly monitor product quality).

SGC has been able to confirm the presence of internal voids in components, or low-quality seals in sealed enclosures. X-ray inspection is also helping to shorten product development lead times. The SwitchGear cubicles consist of many parts, including plastic injection-moulded components, rubber and metal parts; and as almost all components are engineered and designed in-house, X-ray inspection provides an internal insight into prototypes.

R&D engineer Frederik Delobelle says: “We had been looking for years for a solution to optimise the production of one specific component. Thanks to the X-ray and CT images, it became clear what the real issue was, and corrective action was taken. Another important advantage of CT is that for assembled components, it allows us to verify whether the assembly is accurate — for example, if contacts are perfectly aligned — without having to destroy or dismantle the part.”