Safety concerns from issues with diesel exhaust fluid

ESTA is the European association of abnormal road transport and mobile cranes

Concerns in the heavy transport and lifting sectors about engine faults thought to be caused by AdBlue type diesel exhaust fluid (DEF) have been highlighted in a new report.

Research conducted by European transport and crane association ESTA highlights a large number of diesel engine heavy vehicle breakdowns related to the use of AdBlue type DEF. It is also known to be a widespread problem in the agricultural sector.

ESTA has been urging members to send in information about problems with the use of DEF in mobile cranes and self propelled modular transporter (SPMT). The request followed concerns raised at a meeting between association members and representatives of the crane manufacturers through the European Materials Handling Federation, FEM.

Crane rental companies have been reporting problems for months, some of which attributed one third of all on-road breakdowns as being related to the DEF.

ESTA has since decided to try and identify the precise scale and nature of the problem. At the time of writing, 55 companies had responded to ESTA from ten countries. Most were from France, Netherlands and the UK.

Dangerous situations

Problems were reported with wheeled mobile and crawler cranes, trucks and SPMT. Most commonly it was an on-road breakdown, almost half of which were reported as compromising safety. Some reports were of dangerous interruptions to wind turbine and port load-out projects.

Many of the companies had multiple incidents in the last two years, three of them reporting more than 20 over that period.

AdBlue DEF is a mixture of water (67.5 per cent) and urea (32.5 %). It is injected into Euro VI emission standard diesel engine exhausts between the engine exhaust manifold and the catalytic converter to minimise emission of oxides of nitrogen (NOx). Ammonia in the DEF reacts with NOx in the catalytic converter, breaking it down into nitrogen and water vapour in a process called selective catalytic reduction (SCR).

A key concern from the ESTA report is that if the DEF system malfunctions the vehicle engine may lose power or go into a limp mode, possibly even shut down, with potentially dangerous consequences.

Commenting on the new report Ton Klijn, ESTA director, said, “We will continue gathering information and will be consulting with the members of the joint ESTA and FEM European Regulations Workgroup that first raised the issue, and then decide on the next steps.

Safety implications

“What is already clear, however, is that this is a serious issue with considerable safety implications - and it needs to be addressed as a matter of urgency.”

A solution might be for the engine manufacturers to program in a temporary override that would allow the engine to keep operating at full power for a limited period despite throwing error codes and the DEF system malfunction.

ESTA noted that engine manufacturers might be reluctant to invest in diesel engine redesign when their commercial emphasis is on developing electric and other alternative motive power.

AdBlue DEF can crystallise and block its delivery system on the vehicle. Correct storage and use of the liquid is very important. Contaminants in the tank and system can foster crystallisation and with its high water content Adblue freezes at -11 degrees C which, in addition to it not then being injectable, its expansion in the system can cause temporary or permanent faults. It helps to keep the level of AdBlue high in its onboard storage tank and to make sure the engine’s warming system to thaw out frozen DEF is functioning.

For site storage it helps to only have full, sealed containers and keep them indoors and in the dark.

It should be noted that if it is used and stored correctly AdBlue shouldn’t present reliability issues. Alternatives to AdBlue DEF are available, including BlueTec and BlueDEF.