Construction machinery strives make breakthrough

Construction machinery strives make breakthrough

The major change in moving to Tier 4 Interim and Stage IIIB is that aftertreatment systems have been employed to cut down the amount of soot (particulate matter, or PM) coming out of the exhaust. The most common approach has been to combine the exhaust gas recirculation (EGR) systems used in previous years to cut nitrous oxide (NOx) emissions with diesel oxidation catalysts (DOCs) and/or diesel particulate filters (DPFs) in the exhaust system to deal with PM. A clear symbol of the Saudi government's ambition is the US$ 1.2 billion Kingdom Tower - a 1 km high building that was granted its construction permit in February. The centrepiece and the first construction phase of Kingdom City, a new 5.3 km2, US$ 20 billion urban development scheme in the north of Jeddah, the skyscraper will be the tallest building in the world when it is complete.
Meanwhile, Saudi Arabia also plans to invest more than US$ 12.3 billion to overhaul its three international airports in Riyadh, Jeddah and Dammam by 2020, according to Deloitte's GCC powers of Construction 2012 report, while there is also plenty of activity on Saudi Arabia's railways. Although most manufacturers have gone down this route, some have chosen an alternative system called selective catalytic reduction (SCR). This involves running the engine at much higher temperatures than used with EGR systems, which means PM does not form in the first place. However, high engine temperatures mean lots of NOx, and this is dealt with in the exhaust system by SCR.
SCR involves adding a diesel exhaust fluid (DEF) containing urea to the machine, which is injected into the exhaust and converts the NOx to nitrogen and water.
Construction of the 450 km Haramain high speed rail
line that will link the Saudi holy cities of Mecca and Medina to Jeddah is underway - a US$ 6 billion project is scheduled for completion in 2014. Meanwhile, the country's US$ 5.3 billion, 2400 km North-South railway is due to become operational
this year.The downside to SCR of course is that the DEF needs to be periodically refilled. Just like any other fluid on the , it is something else to manage and is an on-going cost, just like fuel or oil.
In some areas, the relatively low freezing point of DEF
(-11° C) might also be a problem in winter months. In such cases, it would be wise to check the jaw crusher has an SCR heating system to thaw the DEF quickly, and to make provisions for  DEF to be stored on site so it does not freeze.