Push Loading with CAT D9L and 651B Scrapers in High-Volume Earthmoving

[MikePhua]

The Powerhouse Behind the Blade
The Caterpillar D9L crawler tractor was introduced in 1980 as a leap forward in dozer design, replacing the D9H and offering a significant boost in horsepower, weight, and pushing capacity. With a gross power rating of 460 HP and an operating weight exceeding 100,000 pounds, the D9L was engineered for mining, large-scale construction, and heavy ripping. Its elevated sprocket design improved undercarriage durability and simplified maintenance—a hallmark of Caterpillar’s modular philosophy.
By the mid-1980s, the D9L had become a staple in coal pits, dam projects, and highway grading operations. Caterpillar sold thousands globally, with strong adoption in North America, Australia, and the Middle East. Its reputation for brute force and mechanical resilience made it a natural candidate for push-loading applications.
Terminology Annotation

• Push Loading: A method where a dozer assists a scraper during loading by pushing from behind, increasing fill speed and reducing cycle time.
  
• Elevated Sprocket: A design where the final drive is raised above the track frame, reducing shock loads and improving component life.
  
• Scraper Bowl: The central cavity of a scraper where material is collected during loading.
  
• Cut Zone: The area of ground being excavated and loaded into scrapers.
  

The 651B Scraper and Its Role in Mass Haul
The Caterpillar 651B is a single-engine, open-bowl scraper designed for high-volume earthmoving. With a bowl capacity of over 44 cubic yards and a top speed exceeding 30 mph, it’s built for long hauls and rapid cycles. Introduced in the late 1960s and refined through the 1970s, the 651B became a backbone of highway and airport construction.
Its large bowl and high horsepower (typically powered by a 475 HP diesel engine) make it ideal for tandem loading, where multiple scrapers operate in sequence. However, in tough soils or short haul scenarios, push loading with a dozer like the D9L dramatically improves efficiency.
Push Loading Dynamics and Technique
Push loading requires precise coordination between the dozer and scraper operator. The D9L approaches the rear of the 651B as it enters the cut zone, applying steady pressure to assist in filling the bowl. Key factors include:

• Synchronizing throttle and gear selection.
  
• Maintaining alignment to avoid side loading.
  
• Communicating via hand signals or radio.
  

The goal is to reduce loading time and maximize fill density. In clay or compacted soils, a solo scraper may struggle to penetrate the cut. The dozer’s added force allows deeper cuts and faster fills, reducing wear on the scraper’s cutting edge and hydraulic system.
Benefits of Push Loading in Production Earthmoving
Push loading offers several advantages:

• Increased production rates: Up to 30% faster loading cycles.
  
• Reduced fuel consumption per cubic yard moved.
  
• Lower wear on scraper drivetrain and hydraulics.
  
• Improved fill consistency and compaction.
  

In a 2009 highway expansion project in Nevada, a fleet of D9Ls push-loading 651Bs achieved over 5,000 cubic yards per hour, outperforming solo scraper operations by 40%. The technique also allowed for tighter cut control and reduced undercutting.
Safety Considerations and Operator Training
Push loading introduces risks if not executed properly:

• Rear-end collisions due to miscommunication.
  
• Track damage from uneven terrain or sudden braking.
  
• Scraper instability during aggressive pushing.
  

To mitigate these risks:

• Operators should undergo joint training sessions.
  
• Machines must be equipped with reinforced push blocks.
  
• Cut zones should be graded for smooth approach and exit.
  
• Spotters or GPS guidance can improve alignment.
  

A contractor in Alberta implemented a push-loading protocol with visual markers and radio check-ins, reducing incidents and improving cycle consistency across a 12-scraper fleet.
Maintenance Impacts and Equipment Longevity
While push loading increases productivity, it also places additional stress on the dozer’s undercarriage and transmission. Recommended practices include:

• Inspecting push blocks and frame welds weekly.
  
• Monitoring transmission temperatures during peak cycles.
  
• Rotating dozers between push and ripping duties to balance wear.
  
• Using synthetic lubricants in high-load applications.
  

Scrapers benefit from reduced hydraulic strain and cutting edge wear, extending service intervals and lowering operating costs.
Recommendations for Fleet Managers

• Deploy push loading in cohesive soil conditions with short haul distances.
  
• Pair dozers and scrapers with compatible horsepower and weight classes.
  
• Track cycle times and fuel usage to quantify efficiency gains.
  
• Schedule joint maintenance reviews for push pairs.
  
• Invest in operator training focused on coordination and safety.
  

Closing Reflections
Push loading with a CAT D9L and 651B scraper is a textbook example of mechanical synergy in earthmoving. When executed with precision and care, it transforms production rates and reduces wear across the fleet. These machines, born of decades of engineering evolution, continue to shape landscapes with brute force and refined technique. In the hands of skilled operators, they turn raw terrain into graded foundation—one synchronized push at a time.