Reducing diesel emissions in construction
With clean Euro VI vehicles dominating European truck fleets, the emphasis on reducing diesel emissions is now switching to other sources, including construction machines. The construction industry is now coming to terms with technologies including exhaust gas recirculation (EGR), Selective Catalytic Reduction (SCR) and Particulate Filters (PM filters), in addition to common-rail injection and full electronic engine control. In doing so, the industry is following in the footsteps of the transport industry and encountering many of the same issues.
Exhaust emissions from non-road mobile machinery (NRMM) engines have been regulated since 1999, in a staged approach. Regulated exhaust pollutants included carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and particulate matter (PM) from the outset.
The construction industry is now poised on the brink of NRMM Stage V emissions limits. These include a drastic tightening of particulate output, to ensure highly-effective technologies such as wall-flow filters are used. Originally due for introduction in June and December 2020, depending upon engine size, these limits have now been postponed for 12 months in response to the Covid crisis.
The delay gives manufacturers a chance to clear stocks of new machinery that would have been sold before the deadline in normal times. Introducing sophisticated emissions control measures to arduous applications such as construction has not been problem-free.
Issues such as fuel cleanliness and the availability of AdBlue at remote locations have posed challenges for operators who had previously been used to operating machines that were designed to cope with adverse conditions.
By all accounts, construction machines are less predictable than their other NRMM counterparts. An industry source tells us:
“The regen schedule is set by the manufacturer, but actual operating conditions can vary widely when compared to the factory test cycle. The machines operate in all kinds of environments, indoors and out, and seasonality also has an influence."
“Unexpected regenerations can also cause operational problems. If a machine is working in a waste transfer station for example, it is in an indoor situation, and surrounded by flammable materials. It has to be moved to a safe location before the process is initiated. Even if working outside, it is likely to have people and other machines in proximity so a clear area must be found.”
For machine operators in all sectors, the fuel burn required to regenerate filters represents an additional cost. This cost can rise drastically if the wrong engine oils are used: if the exhaust has a particulate filter then an oil which is not to the required specification (Low or Medium SAPS), then the filter will clog prematurely with ash. This material is untouched by the regenerative process.
The reduced filter capacity initially increases the required frequency of regenerative burns, but ultimately the ash will fill the filter to the extent that it needs to either be removed for specialist cleaning or replaced with a new component.
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