Since its market launch in 2016 as the world’s largest dozer with hydrostatic drive, the Liebherr PR 776 has exceeded customer expectations in productivity, efficiency and safety, its manufacturer says. Whether it is heavy-duty ripping, grading or other duties, the PR 776 is designed to accomplish them all.
With the PR 766 G8 introduced at the beginning of 2021 and the smaller PR 756 G8, Liebherr now offers a fleet of dozers, ranging from 78,044 to 161,354 pounds of operating weight for tough construction and mining operations.
To further boost use of the machines, while also improving safety, comfort and productivity, customers can tele-operate their machine with Liebherr Remote Control (LiReCon).
During a recent Customer Appreciation Day at its Newport News, Virginia headquarters, Liebherr USA added the PR 776 dozer and several other machines to its available lineup in North America.
Efficiency and performance
The PR 776 is the only mining dozer said to feature an infinitely variable hydrostatic travel drive.
Powered by a Liebherr 12-cylinder, 768-horsepower diesel engine, the PR 776 allows operators to choose between high performance and maximum efficiency via the Eco control system, which enables greater travel drive efficiency in light to medium operations and provides greater fuel savings.
One advantage of the drive concept, according to the company, is the optimization of pressure flow. Hydraulic pressure is based on-demand according to the task. If, for example, the full feed of pressure supply is not required when operating, this is automatically returned. A product manager said the high drive also prevents extra wear on the sprocket teeth because it's not digging in the dirt all the time and requires less horsepower for the same reason.
Liebherr says if required, the engine power is automatically increased for a brief period based on the current requirement. As well as responding more rapidly, the machines offer a significant increase in performance potential and pulling power and a higher reverse speed.
Another key advantage of hydrostatically powered crawler tractors or dozers when working in restricted spaces is the excellent maneuverability with continuous power to both tracks. All steering motions, including turning on the spot, are fast and precise. When involved in ripping work, the ripper can be positioned precisely to enable it to apply power when ripping layers of hard rock.
Intuitive operation and comfort
The cab of the PR 776 is designed for comfort, convenience and simplicity with single joystick operation. The cab noise level is rated at 76 decibels.
The multifunction joystick houses all operating and steering movements at the palm of the hand with only one electronic input element. This operating concept was subjected to rigorous testing at Liebherr and is an important innovation for the 70-metric-ton dozer category, particularly in mining applications, the company says. Operators can quickly find their bearings in the PR776 platform.
All instruments and operating controls within the cab are carefully organized for easy reach. Key functions and machine settings can be adjusted by the operator via the touchscreen display. Eco function parameters, automatic engine speed reduction, travel drive response, steering as well as standard safety functions such as the rearview camera can be all be accessed through the intuitive touchscreen display.
An automatic air-sprung seat detects and adjusts to the operator and deactivates the machine when exiting the cab without a safety lever having to be actuated.
Ready for the future
The LiReCon system is suitable for all dozer applications. It consists of the Liebherr Remote Control teleoperation stand, a state-of-the-art operator workspace with all required controls, and onboard dozer installations: cameras for all different angles and views, microphones for recording machine sounds, radio link receiver and transmitter.
The high-resolution main screen provides complete view on the worksite and around the dozer. The optional active person recognition system identifies people and obstacles in the work area and protects the dozer from damage. Liebherr Remote Control allows fast shift changes between operators and reduces idle and down time. As the operator is no longer tied to the machine, Liebherr Remote Control also enables customers to open new extraction areas in danger zones, extending the range of applications for Liebherr mining dozers.
The design of the Liebherr PR 776 offers all-round visibility, with larger panoramic windows and the downward sloping design of the machine. The standard reversing camera is integrated into the front display and switches to full-screen mode automatically when the dozer is in reverse.
Liebherr was specifically interested in highlighting the ROP/FOPS protection being integrated into the overall cab structure. A normal safety feature, but even with the integration to the cab structure, forward visibility remains unobstructed because the exhaust system and lifting rams were positioned behind the A-pillars. Similarly, side views are not obstructed by the machine's extended work platform, which allows easier access to various service points.
An optional portion of the platform is the illuminated safety ladder. Stored along the working platform, it only causes limited obstruction for the operator. In addition to safer access to the cab platform, the ladder also serves as a lockout for the machine, preventing any motion of the tracks or blade until it is properly stored.
For daily maintenance and service work, Liebherr has included multiple ground-level service points to reduce a tech's need to climb up and down the machine. At ground level there is an emergency stop button, a lockout switch, three quick-change coupling for the engine, splitter box, hydraulic oil and engine oil. In addition, engine compartment doors open to a wide angle, and the cab tilts up for maintenance purposes as needed.
According to the company, depending on the nature of the work, and provided that regular checks are performed, the change interval for Liebherr-plus hydraulic fluid or engine oils can be up to 8,000 hours of operation. Liebherr’s fleet management system LiDAT provides an overview of essential servicing work, warning messages, the machine’s position and actual consumption data and filling levels. Depending on the agreement with the customer, the data is updated several times a day and can be called up whenever needed.
There are also custom-developed different configuration packages in-house for extreme applications such as deserts where extreme climates and low temperatures are common.