Refinements have led to advances in hydraulics, but, while improvements and changes continue, “for the most part, the basics of a hydraulic system are the same,” states Curt Leair, rental accounts service manager for Terex Construction Americas. After all, he says, “hydraulic machines all have the same basic components: the engine, hydraulic pump, hydraulic valve, hydraulic motors, and hydraulic cylinders.”
Refinements have led to advances in hydraulics, but, while improvements and changes continue, “for the most part, the basics of a hydraulic system are the same,” states Curt Leair, rental accounts service manager for Terex Construction Americas. After all, he says, “hydraulic machines all have the same basic components: the engine, hydraulic pump, hydraulic valve, hydraulic motors, and hydraulic cylinders.” [text_ad] But while the same basic concepts of hydraulics have been around for nearly 25 years, including the base architecture of many of the electro-hydraulic (EH) systems we use today, continued advancement has occurred in three main areas of the hydraulics control system: joystick (input), actuator (output), and sensor (feedback) technology, claims Jeff Bauer, senior engineer, hydraulic product verification for John Deere Construction & Forestry. “[They] have matured to a very high level of reliability and cost effectiveness, allowing EH systems to be utilized on almost every piece of construction equipment today.” It was a “basic system in the early days,” judges Mike Fitzgerald, loader product specialist for Bobcat. “Today, they have higher performance and are a longer-lasting, more efficient machine with faster cycling and more versatility.” Engineers have designed high-performance hydraulic systems to give operators the ability to run multiple machine functions simultaneously without sacrificing power or performance. Increased hydraulic pressure and flow can power multiple functions at once, increasing efficiency. Says Leair, “A modern hydraulic system will allow the operator the ability to run boom, stick, and swing functions in a smooth, precise, and efficient manner. These vastly improved hydraulic systems give these machines the strength and agility to allow operators to maximize job-site performance, increase productivity, and generate contractor profitability.” Modern hydraulics systems are more efficient than they used to be, confirms Gary Kassen, engineering director for hydraulics and pneumatics, CNH Industrial. “They’re much smarter than they used to be, and they’re more reliable. That plays into CASE’s larger goal of making equipment more practical and intuitive to use, while also improving on the power needed to get work done.” One of the ways they’ve done that is by switching from fixed displacement work pumps to variable displacement. The pump puts out only as much flow as is needed. “Traditionally, a lot of construction equipment used fixed displacement,” explains Kassen. “If you only needed to make minor adjustments to your work function, most of the flow was being dumped over a relief valve, which created extra heat in the system. By having a variable displacement, you only produce as much flow as needed.” Designing equipment with more pumps also increases efficiency. By putting in multiple pumps and separating steering from the work circuit, it’s possible to match the pumps to the pressures that are needed and reduce throttling losses. Part of the reason modern hydraulics are more efficient today than they were 20 years ago stems from the diminished need for higher horsepower engines to run the system, claims Corey Rogers, marketing manager at Hyundai Construction Equipment. This also contributes to better fuel efficiency. “We use different pump technology: an inline stacked pump technology.” Like CASE, Hyundai offers variable volume piston pumps that vary the flow, based on demand. Instead of fixed displacement pumps running at velocity—whether needed or not—burning fuel unnecessarily. These pumps have the ability to destroke and minimize flow when demand is low.” Over the years, hydraulic systems in construction equipment have evolved from low-pressure, open-center systems to much higher-pressure, closed-center, load-sensing, electro-hydraulic systems, says Deere’s Bauer. “Thirty years ago, 3,000 psi was considered high pressure. Today, that would be considered low pressure. Many implemented hydraulic systems are capable of 4,000 psi. Most excavators are 5,000 psi, and most hydrostatic propel systems run at 6,000 psi.” [text_ad use_post='27747'] The push for higher pressures is to reduce actuator size. Higher pressures allow some equipment designs to use smaller bore cylinders to produce the same power. Smaller cylinders require less flow to achieve the same speed. This in turn allows for a smaller pump. Thus, with higher pressure, the entire system becomes more compact while delivering the same overall power. Power density is one driver in hydraulic advancements. Others include reduced operator fatigue through ease of operation and improved system efficiency. “EH systems provide much easier function control with ‘shorter-throw’ joysticks and greatly reduced lever efforts,” continues Bauer. EH also provides some automated or assisted implement controls designed to reduce cycle times and improve accuracy. Variable displacement pumps coupled with load-sensing hydraulic valves greatly improve system efficiency by pumping oil only when it is required. “The constant displacement gear pump used on most systems years ago pumps oil all the time,” recalls Bauer. “Even when the hydraulics are providing no work, engine power is lost to the hydraulic system due to this constant flow.” In addition to being more efficient, modern hydraulics are also smarter. “Manufacturers have gone from hydro-mechanical systems to electro-hydraulic systems,” says Kassen. “With that comes improved functionality. That may be an automated function, more productivity choices, or just easier-to-select options.” From mechanical levers and pedals to pilot controls, hydraulic controls have evolved to electronic over hydraulic. While a large percentage of contractors still prefer simple basic systems with mechanical foot pedal hydraulic controls because they are reliable and cost less, Fitzgerald says some prefer joysticks for operator comfort. “We try to accommodate operator preference by providing three different style controls: hand lever steering and foot pedal hydraulics; advanced controls system (foot pedals or hand levers for lift arm and bucket); and selectable joystick for the drive and hydraulic functions.” Hydraulic systems are becoming very advanced, and hydraulic pressures are being monitored by the machine control, which then adjusts the hydraulic system to optimum performance. The most dramatic improvement in hydraulics is the interface between controls and the hydraulic system, notes Mike Stark, product specialist of wheel loaders, material handlers, and log loaders for Doosan. “Sensors have been added to [detect] pressure changes in the system so the machine’s hydraulic system can be automatically adjusted to the requirements of the job, he continues. System response times have improved when power is needed.
But while the same basic concepts of hydraulics have been around for nearly 25 years, including the base architecture of many of the electro-hydraulic (EH) systems we use today, continued advancement has occurred in three main areas of the hydraulics control system: joystick (input), actuator (output), and sensor (feedback) technology, claims Jeff Bauer, senior engineer, hydraulic product verification for John Deere Construction & Forestry. “[They] have matured to a very high level of reliability and cost effectiveness, allowing EH systems to be utilized on almost every piece of construction equipment today.”
It was a “basic system in the early days,” judges Mike Fitzgerald, loader product specialist for Bobcat. “Today, they have higher performance and are a longer-lasting, more efficient machine with faster cycling and more versatility.”
Engineers have designed high-performance hydraulic systems to give operators the ability to run multiple machine functions simultaneously without sacrificing power or performance. Increased hydraulic pressure and flow can power multiple functions at once, increasing efficiency. Says Leair, “A modern hydraulic system will allow the operator the ability to run boom, stick, and swing functions in a smooth, precise, and efficient manner. These vastly improved hydraulic systems give these machines the strength and agility to allow operators to maximize job-site performance, increase productivity, and generate contractor profitability.”
Modern hydraulics systems are more efficient than they used to be, confirms Gary Kassen, engineering director for hydraulics and pneumatics, CNH Industrial. “They’re much smarter than they used to be, and they’re more reliable. That plays into CASE’s larger goal of making equipment more practical and intuitive to use, while also improving on the power needed to get work done.”
One of the ways they’ve done that is by switching from fixed displacement work pumps to variable displacement. The pump puts out only as much flow as is needed. “Traditionally, a lot of construction equipment used fixed displacement,” explains Kassen. “If you only needed to make minor adjustments to your work function, most of the flow was being dumped over a relief valve, which created extra heat in the system. By having a variable displacement, you only produce as much flow as needed.”
Designing equipment with more pumps also increases efficiency. By putting in multiple pumps and separating steering from the work circuit, it’s possible to match the pumps to the pressures that are needed and reduce throttling losses.
Part of the reason modern hydraulics are more efficient today than they were 20 years ago stems from the diminished need for higher horsepower engines to run the system, claims Corey Rogers, marketing manager at Hyundai Construction Equipment. This also contributes to better fuel efficiency. “We use different pump technology: an inline stacked pump technology.” Like CASE, Hyundai offers variable volume piston pumps that vary the flow, based on demand. Instead of fixed displacement pumps running at velocity—whether needed or not—burning fuel unnecessarily. These pumps have the ability to destroke and minimize flow when demand is low.”
Over the years, hydraulic systems in construction equipment have evolved from low-pressure, open-center systems to much higher-pressure, closed-center, load-sensing, electro-hydraulic systems, says Deere’s Bauer. “Thirty years ago, 3,000 psi was considered high pressure. Today, that would be considered low pressure. Many implemented hydraulic systems are capable of 4,000 psi. Most excavators are 5,000 psi, and most hydrostatic propel systems run at 6,000 psi.”
The push for higher pressures is to reduce actuator size. Higher pressures allow some equipment designs to use smaller bore cylinders to produce the same power. Smaller cylinders require less flow to achieve the same speed. This in turn allows for a smaller pump. Thus, with higher pressure, the entire system becomes more compact while delivering the same overall power.
Power density is one driver in hydraulic advancements. Others include reduced operator fatigue through ease of operation and improved system efficiency. “EH systems provide much easier function control with ‘shorter-throw’ joysticks and greatly reduced lever efforts,” continues Bauer. EH also provides some automated or assisted implement controls designed to reduce cycle times and improve accuracy.
Variable displacement pumps coupled with load-sensing hydraulic valves greatly improve system efficiency by pumping oil only when it is required. “The constant displacement gear pump used on most systems years ago pumps oil all the time,” recalls Bauer. “Even when the hydraulics are providing no work, engine power is lost to the hydraulic system due to this constant flow.”
In addition to being more efficient, modern hydraulics are also smarter. “Manufacturers have gone from hydro-mechanical systems to electro-hydraulic systems,” says Kassen. “With that comes improved functionality. That may be an automated function, more productivity choices, or just easier-to-select options.”
From mechanical levers and pedals to pilot controls, hydraulic controls have evolved to electronic over hydraulic. While a large percentage of contractors still prefer simple basic systems with mechanical foot pedal hydraulic controls because they are reliable and cost less, Fitzgerald says some prefer joysticks for operator comfort. “We try to accommodate operator preference by providing three different style controls: hand lever steering and foot pedal hydraulics; advanced controls system (foot pedals or hand levers for lift arm and bucket); and selectable joystick for the drive and hydraulic functions.”
Hydraulic systems are becoming very advanced, and hydraulic pressures are being monitored by the machine control, which then adjusts the hydraulic system to optimum performance. The most dramatic improvement in hydraulics is the interface between controls and the hydraulic system, notes Mike Stark, product specialist of wheel loaders, material handlers, and log loaders for Doosan. “Sensors have been added to [detect] pressure changes in the system so the machine’s hydraulic system can be automatically adjusted to the requirements of the job, he continues. System response times have improved when power is needed.
