With the passage of the Clean Air Act, Congress gave the U.S. Environmental Protection Agency (EPA) the responsibility to set emission standards aimed at protecting air quality. Diesel engine and pump system manufacturers have worked with the federal government to achieve a 90 percent reduction in exhaust emissions since the first standards went into effect in 1996. While significant progress has been made, the work is not yet done. The final emissions regulations, which will be fully implemented by 2015, will take particulate matter (PM) and nitrogen oxides (NO) emissions to near-zero levels. To achieve this level, engine manufacturers and components engineers must work together to innovate at all levels. In fact, physically small parts—such as bearings used in hydraulic systems for off-highway equipment—can make a big difference in improving efficiency and lowering emissions.
Steps to Green
During the past 15 years, the U.S. diesel industry has greatly transformed. New, clean-diesel technology made significant strides in reducing emissions and improving efficiency for both on- and off-road vehicles and equipment.
To lead this effort, the EPA took a tiered approach, implementing a series of progressive limitations on emissions from nonroad diesel engines used in off-highway construction equipment ranging from bulldozers to excavators and cranes. These tiered levels are based on the horsepower rating of the machine’s engine.1
The current phase of emissions standards, labeled Tier 4 Interim in the U.S. and Stage IIIB in the European Union, calls on manufacturers to achieve a 90 percent reduction in PM along with a 50 percent drop in NOx. Final Tier 4/Stage IV emissions regulations, to be introduced in 2014 and fully implemented by 2015, will reduce NOx by an additional 80 percent.2
The Role of Manufacturers
To improve efficiency, machinery manufacturers should not only consider components of the vehicle’s engine, but its full system, including secondary operations such as hydraulic piston pumps.
From small loaders to towering cranes, hydraulic transmission systems serve as a key source of motion in off-highway construction equipment. While they have a small physical footprint and mechanically simple design, these systems generate powerful forces in large construction equipment. These sophisticated yet simple systems consist of a hydraulic pump connected to an electric motor or a combustion engine, along with filters, valves and piping, working together to drive torque. An effective hydraulic system is critical to the operation of off-highway machines, and hydraulic pumps are an excellent starting point for engineers who want to enhance efficiency.
Small Parts Make a Big Impact
Within hydraulic pumps, bearings are small but vital components that can affect the overall performance and efficiency of off-highway vehicles. Attached to the shaft of the piston pump, the bearing must facilitate continuous, smooth movement throughout the hydraulic pump’s lifetime, requiring minimal energy to rotate the drive shaft and power the machine.
Recent innovations, such as composite bearings, are typically formed from a metal backing with a liner made of a fluoropolymer compound. One of the most effective fluoropolymers is polytetrafluoroethylene (PTFE). Within composite bearings, the PTFE liner functions as a dry lubricant, ensuring consistent controlled friction during their long life. Decreased friction between rotating parts facilitates movement, translating into lower energy consumption, enhanced pump efficiency and ultimately, a reduction in harmful emissions.
The Race to Innovate: Customization Is Key
For off-highway construction equipment, each application is unique, requiring collaboration between manufacturers and their suppliers. Application engineers must begin by understanding unique system parameters—including required load, lubrication and speed of the machinery. Low friction and wear resistance properties can be achieved by examining mating components, including shaft and housing construction, to develop a custom solution.
Partnering with a supplier that has the ability to customize its offerings coupled with experience in different applications and a solid understanding of the latest and upcoming emissions regulations will help speed the time to market. By using innovative solutions such as composite bearings in hydraulic piston pumps, off-highway construction equipment manufacturers can achieve reduced emissions to comply with regulations and enhance efficiency. As the industry evolves to Final Tier 4/Stage IV emissions regulations and beyond, its collaboration will improve the efficiency of operations, air quality and public health.
The EPA estimates that when the full inventory of older, nonroad engines is replaced by Tier-4 engines, emissions will be reduced annually by 738,000 tons of NOx and 129,000 tons of PM.3
By 2030, the EPA estimates that 12,000 premature deaths, 8,900 hospitalizations, 15,000 heart attacks, 6,000 asthma emergency room visits and 280,000 respiratory cases in children will be prevented annually because of the implementation of Tier 4 emissions standards.4