 The Caterpillar 627G scraper transmission is electronically controlled and automatically synchronizes to the tractor transmission gear selection. The planetary powershift transmission has four forward gears and one reverse. |
The new Caterpillar 621G, 623G, and 627G wheel tractor-scrapers feature a new operator station and electrohydraulic controls for enhanced productivity and operator comfort. The new controls include a single joystick in place of three implement control levers. The models also feature powertrain improvements that include an electronically controlled tractor engine for high performance and improved efficiency. The G-Series scrapers build on the performance characteristics of the 621F, 623F, and 627F, which the new machines replace.
The 621G is a 15.3-m3 (20-yd3) capacity open-bowl scraper that achieves optimum productivity when it is push-loaded. The 621G is also available with an auger system in the bowl, which gives the machine self-loading capability in a wide ranage of material and expands the capacity to 16.1 m3 (21 yd3). The 623G is a 17.6-m3 (23-yd3) self-loading elevating scraper that conditions materials as the elevator flights lift it into the bowl.
The 627G is a 15.3-m3 (20-yd3) tandem-powered scraper. Twin engines give the 627G the ability to handle steep grades and poor underfoot conditions. The machine can load independently or it can be push-loaded. It is available in two additional arrangements - an auger scraper arrangement, which gives the machine self-loading capability and expands the capacity to 16.1 m3 (21 yd3), and a push-pull configuration, designed to work in tandem with another 627 for a high production-to-cost ratio.
Caterpillar designed and built the new G-Series scrapers to provide the lowest cost per yard in site development and road construction projects under 380,000 m3 (500,000 yd3). Primary applications for the scrapers include hauling material distances greater than 300 m (1000 ft). The 621G and 627G are both sized to work well with D8 and D9 push tractors.
The single lever implement control of the new operator environment combines the traditional three implement levers into one joystick. The operator can raise and lower the bowl, actuate the apron and ejector, set the elevator speed and direction, actuate the auger, and operate the bail with the single joystick. The transmission hold and cushion hitch switches are incorporated into the joystick as well.
The electronic transmission controller simplifies gear selection and allows the operator to program the top gear for matching travel speeds to the rest of the fleet. A throttle lock enables the operator to maintain engine speed during the haul cycle without pressing on the throttle.
The completely redesigned cab includes a revised steering column and control layout to provide 11% more space for increased operator comfort and reduced fatigue. A new Caterpillar Comfort seat with air seat suspension offers four different swivel lock points to allow proper positioning in relation to the joystick. The new instrument panel features a quad gauge cluster that includes fluid level and temperature displays. An electronic speedometer/tachometer has digital displays for vehicle speed and actual gear indication. The improved electronic monitoring system, EMS II, monitors machine status and provides real-time information to the operator. Air conditioning is now standard in the rubber-mounted cab. According to Caterpillar, the 627G is the first tandem-powered wheel tractor-scraper to offer scraper engine start-up and monitoring directly from the cab.
The six-cylinder Cat 3406E Electronically Controlled Unit Injection (EUI) diesel engine has a dual power capability of net 246/272 kW (330/365 hp), which increases power when the machine is operating in higher gear ranges for faster cycle times and greater gradeability. It also supplies more power when operating the elevator or auger mechanisms. The scraper engine on the tandem-powered 627G is the Cat 3306 DITA, which has a net power of 168 kW (225 hp).
EUI is a high-pressure, direct-injection fuel system that improves torque rise for more power in the cut, improves fuel efficiency, and reduces emissions. The system provides infinitely variable injection timing to maintain peak performance. The 3406E Advanced Diesel Engine Management system uses innovative software and hardware to monitor, control, and protect the engine. It has air-to-air aftercooling for reduced air inlet manifold temperature.
The fuel capacity of G-Series machines has been increased to allow 11 h of operation between refueling. The machines also feature the Advanced Modular Cooling System (AMOCS), which replaces the folded core radiator used on the F-Series scrapers. AMOCS is designed to improve cooling capacity and serviceability.
The new tractors feature an electronically controlled planetary powershift transmission with eight forward speeds and one reverse speed. Electronic Control Throttle Shifting automatically synchronizes engine speed to transmission speed during shifting to reduce powertrain stress, increase component life, and provide smoother shifts.
Many of the maintenance points on G-Series machines have been centralized under the right-side engine enclosure for simplified maintenance. The fluid filters of the new machines are all spin-on style with the exception of the main hydraulic filter. According to Caterpillar, spin-on filters decrease maintenance time and reduce the chances of system contamination.
