Tightening engine exhaust emission regulations have meant that tractor manufacturers have had to develop new ways to meet them. The introduction of each round of regulations, referred to as a tier or stage, has been challenging for manufacturers. It has also meant a hefty tractor price increase as each stage is met.
As the various emission regulations came into force over the years, there were two distinct paths they could take in dealing with diesel exhaust emissions.
There were two polluting elements of a tractor’s exhaust emissions that needed to be dealt with to comply with emission regulations. One was the soot produced by the engine and the other was the nitrous oxides (NOx).
While both soot and NOx had to be dealt with, manufacturers placed their primary focus on one or the other. This gave the two distinct paths of dealing with engine exhaust emissions that we have seen over recent years.
Roughly speaking, the following are those two paths. EGR reduced NOx and when combined with variable geometry turbos and latterly the addition of a DPF-Diesel Particulate Filter, dealt with the sooty aspect of emissions. The downside is that EGR required a more efficient cooling package for the engine and DPF requires regeneration to burn off the soot it catches.
The other route was focused on producing less soot and used SCR (selective catalytic reduction) with DEF (diesel exhaust fluid (AdBlue)) to deal with NOx. SCR-using DEF was generally considered to be the less intrusive method of controlling emissions as it did not interfere with the goings-on in the engine, merely treating the NOx emissions as they left the engine. Having to use AdBlue to clean up the NOx emissions did introduce an extra running cost. Ultimately, it is recognised that all manufacturers will have to use DEF at some stage as emission regulations get tighter.
Learning curve
AdBlue was considered by many to be the “cleaner” of emission control systems and placed less pressure on the engine. Much of that theory was based on the experience of the on-road sector where stricter emission regulations were introduced at a far earlier stage.
When emission regulations finally introduced SCR and DEF into the agri-sector, there was a lot to be learned.
It was thought that agricultural machinery and tractors would use a lot more than they actually did.
Why? Estimated DEF consumption levels were based on the on-road or truck industry. The work rate of a truck engine is far more consistent than that of an agricultural machine. A truck driver aims to have the truck pulling at its top permissible speed at all times to cover mileage as quickly and as consistently as possible.
But loads on a tractor’s engine vary enormously. So unless it is in a constant power-demanding operation such as rotavating and ridging for potatoes, then its DEF usage will likely be miserly. That is good for the pocket.
The initial estimated use of DEF did lead to other problems. These included over-stocking of DEF based on anticipated rate of use and storing the DEF outside. DEF is a mixture of urea and water and if stored outside in a clear container such as a bunded tank, the sunlight and heat can separate water and urea.
Contamination
Contamination of the DEF in the tank of the tractor was a common problem for users initially. Some manufacturers install a restrictor in the neck of the DEF tank but these are often removed to facilitate filling from a 10-litre or 20-litre plastic can.
Accidentally putting diesel in the DEF tank should not be ignored. The tractor won’t use DEF until it comes under load, so notify your dealer beforehand and they will clean and flush out the DEF tank. It becomes more complex and expensive if the tractor has started to use the cocktail of DEF and diesel.
If fuel additives are accidentally added to a DEF tank, they can cause problems and need to be dealt with in the same way. Some additives will cause the DEF to change into a gel-like substance and make it very difficult to clean out.
The other mix-up is even more dangerous – accidentally putting DEF in the tractor’s fuel tank. DEF is mildly corrosive, but a tractor’s fuel system is extremely sensitive to such a substance. Starting the tractor with DEF in the tanks could cause thousands of euros worth of damage to the tractor’s injection system and engine. If you have accidentally put DEF in your diesel tank, do not start the tractor and call your dealer immediately to flush out the tank.
On a tractor fitted with SCR it is very, very important that it is worked hard from time to time. This is to ensure that soot and hydrocarbons do not build up in the catalyst of SCR unit within the exhaust system. Replacing a blocked or damaged SCR/exhaust will be an expensive exercise.
Using high-sulphur diesel will also cause huge problems with the DEF injection system. Using high-sulphur diesel produces NOx gases and the DEF system tries to compensate by injecting more urea into the SCR unit.
In effect, it overdoses the exhaust system with urea and this causes crystallisation of the urea in the injector and exhaust system, ultimately blocking or partially blocking one or both. A faulty NOx downstream sensor can have the same effect but high-sulphur diesel will cause overdosing and crystallisation.
DEF quality
DEF is a mixture of urea and water, with the optimal mixture ratio being around 32.5% urea and 67.5% demineralised water. Too far outside of this ratio can and will cause problems, ultimately resulting in the tractor switching off its DEF system and going into limp-home mode.
If in doubt about the quality of your DEF, many dealers are now suitably equipped to test the DEF to ensure its quality is up to spec. Many dealers are similarly equipped to test all of an engine’s liquids, including diesel, engine oil and coolant.
DEF/AdBlue packaging has a date code to indicate when the fluid was manufactured. Use the date code to determine the age of the solution. The solution can break down over time and it is important to use solution that is within the approved lifespan.
The date code is an 11-digit number on the box that will be similar to the example below:
CP11061 0995
Ignore the “CP” First two digits are the year of manufacture, so “11” indicates 2011. The next three digits are days left in the year, 061 indicates this is day 304 of 365 days in the year. 61 days remain in 2011.
Storage and handling
As DEF is a water-based solution, it will freeze at around -11 degrees Celsius. Take precautions when using DEF in extreme low-temperature conditions. The process of freezing DEF has no effect on its quality or performance.Leave room for expansion in the DEF tank. It is reported that DEF will expand upon freezing by upward of 7%. When storing equipment overnight or longer in temperatures that could result in DEF freezing, it is important to make sure the DEF tank on the equipment is not completely full to allow for this expansion. This will also help to prevent cracking of the storage container. During winter, once the tractor is started, the DEF will thaw quickly and return to its usable state.Always store DEF indoors. DEF packages and bulk storage should be kept indoors in temperature-controlled environments.As DEF is mildly corrosive, it should be stored in plastic or stainless steel containers.The injectors that meter DEF into the exhaust stream have tight tolerances, just like tractor engine fuel injectors. Many tractor SCR systems have a cartridge filter inside the pumping unit to protect these injectors and they have a recommended 1,200-hour service interval. Change the filter on the pumping unit at the time recommended.The storage life of DEF will vary. As it is made from urea, it will degrade in sunlight and higher temperatures. In good storage conditions, where there is a proper container, away from direct sunlight, in an even temperature, DEF can maintain its qualities for about 12 months.You need to handle DEF with the same care as diesel. Tractors use DEF sensors to continually analyse the quality of the DEF being consumed. These sensors will trigger a fault code whenever an imbalance such as dirt or water is detected. So keep it free of any contaminants and moisture and store it in a proper container kept in a cool, shaded place.
Tightening engine exhaust emission regulations have meant that tractor manufacturers have had to develop new ways to meet them. The introduction of each round of regulations, referred to as a tier or stage, has been challenging for manufacturers. It has also meant a hefty tractor price increase as each stage is met.
As the various emission regulations came into force over the years, there were two distinct paths they could take in dealing with diesel exhaust emissions.
There were two polluting elements of a tractor’s exhaust emissions that needed to be dealt with to comply with emission regulations. One was the soot produced by the engine and the other was the nitrous oxides (NOx).
While both soot and NOx had to be dealt with, manufacturers placed their primary focus on one or the other. This gave the two distinct paths of dealing with engine exhaust emissions that we have seen over recent years.
Roughly speaking, the following are those two paths. EGR reduced NOx and when combined with variable geometry turbos and latterly the addition of a DPF-Diesel Particulate Filter, dealt with the sooty aspect of emissions. The downside is that EGR required a more efficient cooling package for the engine and DPF requires regeneration to burn off the soot it catches.
The other route was focused on producing less soot and used SCR (selective catalytic reduction) with DEF (diesel exhaust fluid (AdBlue)) to deal with NOx. SCR-using DEF was generally considered to be the less intrusive method of controlling emissions as it did not interfere with the goings-on in the engine, merely treating the NOx emissions as they left the engine. Having to use AdBlue to clean up the NOx emissions did introduce an extra running cost. Ultimately, it is recognised that all manufacturers will have to use DEF at some stage as emission regulations get tighter.
Learning curve
AdBlue was considered by many to be the “cleaner” of emission control systems and placed less pressure on the engine. Much of that theory was based on the experience of the on-road sector where stricter emission regulations were introduced at a far earlier stage.
When emission regulations finally introduced SCR and DEF into the agri-sector, there was a lot to be learned.
It was thought that agricultural machinery and tractors would use a lot more than they actually did.
Why? Estimated DEF consumption levels were based on the on-road or truck industry. The work rate of a truck engine is far more consistent than that of an agricultural machine. A truck driver aims to have the truck pulling at its top permissible speed at all times to cover mileage as quickly and as consistently as possible.
But loads on a tractor’s engine vary enormously. So unless it is in a constant power-demanding operation such as rotavating and ridging for potatoes, then its DEF usage will likely be miserly. That is good for the pocket.
The initial estimated use of DEF did lead to other problems. These included over-stocking of DEF based on anticipated rate of use and storing the DEF outside. DEF is a mixture of urea and water and if stored outside in a clear container such as a bunded tank, the sunlight and heat can separate water and urea.
Contamination
Contamination of the DEF in the tank of the tractor was a common problem for users initially. Some manufacturers install a restrictor in the neck of the DEF tank but these are often removed to facilitate filling from a 10-litre or 20-litre plastic can.
Accidentally putting diesel in the DEF tank should not be ignored. The tractor won’t use DEF until it comes under load, so notify your dealer beforehand and they will clean and flush out the DEF tank. It becomes more complex and expensive if the tractor has started to use the cocktail of DEF and diesel.
If fuel additives are accidentally added to a DEF tank, they can cause problems and need to be dealt with in the same way. Some additives will cause the DEF to change into a gel-like substance and make it very difficult to clean out.
The other mix-up is even more dangerous – accidentally putting DEF in the tractor’s fuel tank. DEF is mildly corrosive, but a tractor’s fuel system is extremely sensitive to such a substance. Starting the tractor with DEF in the tanks could cause thousands of euros worth of damage to the tractor’s injection system and engine. If you have accidentally put DEF in your diesel tank, do not start the tractor and call your dealer immediately to flush out the tank.
On a tractor fitted with SCR it is very, very important that it is worked hard from time to time. This is to ensure that soot and hydrocarbons do not build up in the catalyst of SCR unit within the exhaust system. Replacing a blocked or damaged SCR/exhaust will be an expensive exercise.
Using high-sulphur diesel will also cause huge problems with the DEF injection system. Using high-sulphur diesel produces NOx gases and the DEF system tries to compensate by injecting more urea into the SCR unit.
In effect, it overdoses the exhaust system with urea and this causes crystallisation of the urea in the injector and exhaust system, ultimately blocking or partially blocking one or both. A faulty NOx downstream sensor can have the same effect but high-sulphur diesel will cause overdosing and crystallisation.
DEF quality
DEF is a mixture of urea and water, with the optimal mixture ratio being around 32.5% urea and 67.5% demineralised water. Too far outside of this ratio can and will cause problems, ultimately resulting in the tractor switching off its DEF system and going into limp-home mode.
If in doubt about the quality of your DEF, many dealers are now suitably equipped to test the DEF to ensure its quality is up to spec. Many dealers are similarly equipped to test all of an engine’s liquids, including diesel, engine oil and coolant.
DEF/AdBlue packaging has a date code to indicate when the fluid was manufactured. Use the date code to determine the age of the solution. The solution can break down over time and it is important to use solution that is within the approved lifespan.
The date code is an 11-digit number on the box that will be similar to the example below:
CP11061 0995
Ignore the “CP” First two digits are the year of manufacture, so “11” indicates 2011. The next three digits are days left in the year, 061 indicates this is day 304 of 365 days in the year. 61 days remain in 2011.
Storage and handling
As DEF is a water-based solution, it will freeze at around -11 degrees Celsius. Take precautions when using DEF in extreme low-temperature conditions. The process of freezing DEF has no effect on its quality or performance.Leave room for expansion in the DEF tank. It is reported that DEF will expand upon freezing by upward of 7%. When storing equipment overnight or longer in temperatures that could result in DEF freezing, it is important to make sure the DEF tank on the equipment is not completely full to allow for this expansion. This will also help to prevent cracking of the storage container. During winter, once the tractor is started, the DEF will thaw quickly and return to its usable state.Always store DEF indoors. DEF packages and bulk storage should be kept indoors in temperature-controlled environments.As DEF is mildly corrosive, it should be stored in plastic or stainless steel containers.The injectors that meter DEF into the exhaust stream have tight tolerances, just like tractor engine fuel injectors. Many tractor SCR systems have a cartridge filter inside the pumping unit to protect these injectors and they have a recommended 1,200-hour service interval. Change the filter on the pumping unit at the time recommended.The storage life of DEF will vary. As it is made from urea, it will degrade in sunlight and higher temperatures. In good storage conditions, where there is a proper container, away from direct sunlight, in an even temperature, DEF can maintain its qualities for about 12 months.You need to handle DEF with the same care as diesel. Tractors use DEF sensors to continually analyse the quality of the DEF being consumed. These sensors will trigger a fault code whenever an imbalance such as dirt or water is detected. So keep it free of any contaminants and moisture and store it in a proper container kept in a cool, shaded place.
This is a subscriber-only article
SHARING OPTIONS: