The introduction of sophisticated electronics necessary to meet the latest engine emissions regulations gives excavator manufacturers new tools to increase hydraulic system efficiency. In addition, manufacturers have found many ways to increase the efficiency of the hydraulic systems through improved valve designs and optimized work modes.
For example, Caterpillar increased the hydraulic efficiency of its E-Series excavators by changing the valve layout. “On many of the D-Series models, we had side-by-side valves,” notes Kent Pellegrini, global excavator specialist. “We went to back-to-back valves.” The 90° elbows in the system are replaced by straight lines, which eliminate hydraulic lines and pressure spike points. “When you reduce pressure spikes, it helps eliminate heat and also helps increase hydraulic power.”
By reducing pressure spikes, less pressure is required from the pump. “The more pressure coming out of that pump, the harder you have to turn the engine to get that pressure,” Pellegrini explains. “If you can reduce that engine load coming into the pump by being more efficient with the valve, you can save more fuel and you will maximize hydraulic power. The pure hydraulic power that we get out of those valves is just exceptional. ”
Caterpillar dedicated resources to improve the oil flow within the main valve, as well. “Where we might have had a hard corner, we rounded it so the oil flow doesn’t restrict against the hard corner,” says Pellegrini. The passages in the valve were improved to make them more efficient. “That improves controllability.”
The back-to-back valve also allows easier access. Operators will notice the clean appearance when they look down into the well. Hose lengths were reduced and the hoses are mounted more directly.
In order to maximize hydraulic horsepower while reducing fuel consumption, you must find ways to reduce the amount of flow that is put to the main valve. This is possible with advanced electronics, such as the boom regeneration valve. “That allows us to run the engine at a lower speed but still maintain the hydraulic power,” Pellegrini notes.
Consider an excavator that does not have an electronic regeneration valve. The system works by populating oil from the head end of the cylinder to the rod end. “The oil flow after I use my stick goes right back to the hydraulic tank,” says Pellegrini. “Then it has to come back from the hydraulic tank through the main valve into the cylinder.”
The electronic regeneration valve makes this process more efficient. “We put a loop in the system that recirculates oil on the head end of the rod into the cylinder. So we isolate it in one area,” says Pellegrini. “That reduces the amount of oil you have to put through the main valve. Therefore, the engine doesn’t have to turn as hard to run the pump. Energy loss is minimized when you recirculate from the head end to the rod end electronically. It is done by a solenoid on the main control valve. It is a very simple device.”
This system has also eliminated hydraulic lines. “We do it more internally,” says Pellegrini. “Therefore, we don’t have to run oil flow through those lines anymore. That helps with fuel reduction.”
Between the combination of the new valve design and the electric regeneration valve, Caterpillar has managed to increase fuel efficiency by approximately 2%.
Matching power to the application
Fuel efficiency has also been the driving force behind the most recent advancements in the Volvo Construction Equipment excavator line. The company uses a smart hydraulic system that features bucket regeneration, boom priority and reduced internal losses in the hydraulic circuit for increased efficiency and productivity, as well as lower fuel consumption.