Injection moulding and welding replaces blow moulded tank

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In order to comply with Euro 6, diesel passenger cars also need to convert to the urea technology familiar to us from heavy goods vehicles (HGVs). This calls for additional tanks. Röchling has been exhibiting the first volume production tanks for the Audi diesel. After considering various concepts, Röchling decided against a blow moulded tank. The new system is implemented using injection moulded half shells that are welded together in the classic manner to create a tank.

Tank welded together from injection moulded half shells (photos: Röchling)

 

Following their initial use in commercial vehicles, selective catalytic reduction (SCR) systems are being increasingly used in passenger vehicles with diesel engines. The process of selective catalytic reduction serves to convert nitrogen oxides in exhaust gas into nitrogen and water without unwanted by-products using a urea solution. The initial application of this system has been demonstrated by Audi at the IAA.

Röchling expects that in the future automobile manufacturers will also use the SCR systems in smaller or less powerful vehicles due to ever more stringent exhaust standards.

Optimal use of space

In order to reduce package space in the vehicle, the challenge lies in developing a tank system that is as compact as possible. With space and weight optimised as well as functionally integrated solutions, the system supplier ensures a high degree of flexibility combined with cost effective implementation.

For example, the plastic tanks manufactured using injection moulding are advantageous because of their low weight and use of corrosion resistant materials. Furthermore, the tank system satisfies all additional requirements posed by the urea solution. The strict sealing guidelines for AdBlue are met. A special valve in the sealing cap permits pressure equalisation. The system is practically maintenance free.

Precision creates reliability

A cleverly designed metering module measures the temperature and helps ensure that the solution is automatically thawed and warmed at temperatures below -11°C. At the same time, the metering module integrates additional functions: it facilitates fluidity by using a pump and avoids impurities by using a filter. In addition, given the increasing on-board diagnostic (OBD) requirements, using a two-pin plastic sensor developed for water cooled degas bottles is conceivable for continuously measuring levels and urea quality. Disruptive sloshing noises were minimised by design, while wall thicknesses were kept both safe and weight conserving by using simulation tools. The simulation of flows and even the defrosting processes mathematically ensured flawless functioning even before the first vehicle test.

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