Industry warned to take care with SCR exhaust systems


Operators should take care with diesel exhaust fluid (DEF) used in the catalytic converter

Industry warned to take care with SCR exhaust systems
Industry warned to take care with SCR exhaust systems

By Gary Worrall | September 27, 2011

While SCR Technology is recognised as an efficient way of cleaning exhaust gases in heavy trucks, operators should take care with diesel exhaust fluid (DEF) used in the catalytic converter.

This is the warning from UD Trucks’ Product Planning and Engineering Manager Mark Hammond.

While Hammond says he has only seen about six cases of catalytic converter failure in SCR-equipped trucks since UD introduced the technology to Australia in 2005, he says DEF contamination can be a big issue.

"The only issues have been contamination, but that can still be a problem, so we urge great care with DEF," says Hammond.

In one instance, he says staff had stored the DEF in an old oil drum, which still had ill residue in it, before it was poured into the tank on the truck. Hammond says the oil residue entered the SCR system and damaged the catalytic converter in the exhaust, with the truck returned to the workshop for repairs.

"We were able to trace the oil residue back to the operator by testing the DEF, it showed the oil contamination and we worked back from there," he says.

In a training brochure developed by UD Trucks operators are warned to not even turn the ignition on if there is suspected contamination because even a short run time will damage the pump module.

Cummins South Pacific, which supplies SCR-equipped engines to a number of manufacturers, is also concerned operators treat DEF with care.

"Diesel Exhaust Fluid (DEF) or Adblue as it is known is a carefully blended aqueous urea solution of 32.5 percent high purity urea and 67.5 percent deionized water," Scott Alexander, who manages Cummins’ automotive business, says.

"If a non-DEF substance is accidentally entered into the SCR system, it will recognize solutions other than DEF, and the DEF indicator light will appear notifying the driver."

He says DEF containers should state and display the certification of the American Petroleum Institute (API), German Institute of Standardization DIN70700, the International Organization for Standardization ISO 22241-1, and meet AUS – 32 specifications, which ensure it has the correct purity and concentration of urea.

Alexander says Cummins has put preventative measures in place to help protect operators from filling the DEF tanks with diesel.
"The standard nozzle diameter for dispensing DEF has been designed at 19mm versus the standard diesel fuel nozzle diameter which is 22mm, in addition, the tank cap for the DEF tank will be blue to further differentiation from the diesel tank," he says.

Hammond says while he is not aware of any DEF that does not meet the Australian standard, it is important operators only use clean fluid that is stored properly to prevent damage.

"We do a lot of work with our dealers, and also with customers, to explain the need to keep the DEF supply clean and free of contamination. It is vital it is stored properly."

Hammond says DEF can react with a variety of substances, including steel, aluminium, copper and brass, so customers are advised to only use ‘virgin’ containers made from materials such as polypropylene or stainless steel. Any containers or pumps with internal plating or painting must not be used.

"At the end of the day, contamination is not a warranty issue," Hammond says.

Alexander is even more specific in his response, saying regardless of the contaminant, Cummins does not take responsibility.

"Cummins is not responsible for failures caused by incorrect oil or fuel or by water or diesel exhaust fluid, catalytic reagent, dirt or other contaminants in the fuel, oil, diesel exhaust fluid, catalytic reagent or intake air system," he says.

Alexander says in the "worst case scenario" after contamination, both the dosing pump and the exhaust catalyst could need to be replaced.

Have you had a problem with DEF in your SCR trucks? Email your story to Gary Worrall

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