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Catalytic Precious Metal Control

Looking inside catalytic converters

More than 85% of cars sold globally each year are fitted with catalytic converters. They help to cut vehicle pollution so it is important they are produced to the highest standards. Vince Deery, sales & marketing director at 3DX-RAY, explains the importance of looking inside them.

Governments introduced emission laws to control air pollution and catalytic converters quickly became a popular way to help meet these new standards. By converting toxic by-products of vehicle engines, using an internal combustion technique that catalyses chemical reactions, catalytic converters produce cleaner emissions. Governments have laid down strict regulations on the performance characteristics of these devices to ensure that emissions targets are met.

However, the actual catalyst inside these popular devices are often constructed of a substrate coated with a number of layers of precious metal – platinum, palladium or rhodium for example. As a result manufacturing catalytic converters is a delicate balancing act between delivering the required performance, and minimising material waste. It is therefore no wonder that manufacturing processes have become progressively more advanced to ensure catalytic converters are meeting these twin, competing requirements.

Inside a converter

The catalysts are transferred to the core substrate of the converters through a series of ‘washcoat’ layers. The insulated chamber that contains the substrate needs to work at incredibly high temperatures, oxidizing the hydrocarbons and carbon monoxide given off by vehicles exhausts and it is critically important that these washcoats are executed correctly.
This means they must cover the substrate exactly as designed, this may be a full coating or only partial coating, whilst if there is an overlap of coatings required this must be at exactly the right amount to ensure efficacy of the catalyst. The quality of this manufacturing process is paramount otherwise the catalytic converter will not function correctly, wasting the expensive catalyst material.

Of course these processes are calibrated on the production line, but it is vitally important to be able to check the quality of the wash coat applied to the core substrate. By monitoring the manufacturing process operators can acquire information about process trends to enable timely control and minimise potential wastage and scrap.

Traditionally manufacturers would use destructive testing techniques, dismantling a few items in each batch on the production line to check if the process has been successful. However, the obvious downside to this technique is that the items being tested become scrap and the materials are wasted. It also means you can only test a limited number of items in each batch, rather than performing 100% screening.

The power of x-rays

3DX-RAY has worked with a number of customers who wanted to minimise this waste and institute a method of testing that provided 100% in-line inspection, improving efficiency and also guaranteeing the manufacturing integrity of each and every product.

X-ray inspection can deliver this testing regime, offering a non-destructive way of seeing inside the catalytic converters and providing the capability to detect, measure and analyse features hidden from view and confirm the quality and integrity of the product. X-ray systems deliver a rapid pass/fail result without having to dismantle the converter.

As a result x-ray systems minimise waste and scrap while providing a powerful laboratory tool improving the understanding of the manufacturing process and aftersales analyses, reducing product development and evaluation cycles. Using sophisticated image capture and processing software operators can not only ‘see’ sub-millimetre details inside an object, but can also measure and analyse them providing valuable data for quality and process control.

Many of our customers first turn to x-ray inspection as an alternative to destructive batch testing, the benefits of x-ray screening means that many have moved away from one off checks to integrating the screening tools into the production line, ensuring the quality of every item manufactured.

The MDXi x-ray system, from 3DX-RAY, is capable of measuring substrate coatings or multiple washcoats to identify artifacts and defects, such as gaps and overlaps that could all lead to the failure of the catalytic converter. It provides 100% production control at full production line speed.

Guaranteeing quality and process control

The layering process of the washcoats on a catalytic converter is intricate and it is imperative that it is done correctly. If errors are introduced into the manufacturing process then expensive materials can be needlessly wasted and the performance of the catalyst is substantially reduced.

In such a critical, tightly regulated product sector, these are crucial issues. X-ray inspection is a robust, proven tool that can guarantee the efficiency of the production processes and of the final product, significantly reducing the risk involved in a high-volume, manufacturing sector.