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Understanding the Task: Excavator-Hammer Rock Breaking
Rock breaking with a hydraulic hammer mounted on an excavator is a common method for site preparation, trenching, and demolition in areas with hard or fractured rock. In one scenario, a contractor asked how much moderately hard rock a CAT 345 excavator equipped with a 10,000 lb hydraulic hammer could break per hour or per day. While the question seems straightforward, the answer depends on multiple variables—rock type, hammer energy, operator skill, and site logistics.
Terminology Explained
- Hydraulic Hammer (Breaker): A percussion tool powered by hydraulic flow, used to fracture rock or concrete
- Impact Energy: The force delivered per blow, typically measured in joules or foot-pounds
- Moderately Hard Rock: Rock with a compressive strength of ~15,000–25,000 psi, such as limestone or weathered granite
- Production Rate: The volume or weight of material broken per unit time, often measured in tons/hour
Estimating Production Rates
A CAT 345 excavator paired with a 10,000 lb hammer is a high-output setup. Assuming the rock is moderately hard and not reinforced or embedded with steel, typical production rates range from:
A contractor in Colorado used a Volvo EC480 with a 9,000 lb hammer to break granite for a road cut. Despite the rock’s hardness (~30,000 psi), they averaged 60 tons/hour by pre-drilling stress relief holes and using a skilled operator. They noted that hammer alignment and consistent tool pressure were critical to maintaining productivity.
Additional Parameters and Suggestions
1. Match Hammer to Excavator
While a CAT 345 with a 10,000 lb hammer is capable of breaking hundreds of tons of rock per day, actual productivity depends on more than machine specs. Rock type, operator skill, tool condition, and site layout all play a role. By approaching rock breaking as a system—balancing equipment, technique, and maintenance—contractors can maximize output and minimize downtime. In the end, the hammer is only as effective as the hands and habits behind it.
Rock breaking with a hydraulic hammer mounted on an excavator is a common method for site preparation, trenching, and demolition in areas with hard or fractured rock. In one scenario, a contractor asked how much moderately hard rock a CAT 345 excavator equipped with a 10,000 lb hydraulic hammer could break per hour or per day. While the question seems straightforward, the answer depends on multiple variables—rock type, hammer energy, operator skill, and site logistics.
Terminology Explained
- Hydraulic Hammer (Breaker): A percussion tool powered by hydraulic flow, used to fracture rock or concrete
- Impact Energy: The force delivered per blow, typically measured in joules or foot-pounds
- Moderately Hard Rock: Rock with a compressive strength of ~15,000–25,000 psi, such as limestone or weathered granite
- Production Rate: The volume or weight of material broken per unit time, often measured in tons/hour
Estimating Production Rates
A CAT 345 excavator paired with a 10,000 lb hammer is a high-output setup. Assuming the rock is moderately hard and not reinforced or embedded with steel, typical production rates range from:
- 50–100 tons per hour in optimal conditions
- 400–800 tons per day with continuous operation and minimal repositioning
- Lower rates (~30–60 tons/hour) in fractured or layered rock requiring repositioning
- Rock density and fracture pattern
- Hammer frequency (blows per minute)
- Operator technique and positioning
- Downtime for repositioning, tool wear, or refueling
A contractor in Colorado used a Volvo EC480 with a 9,000 lb hammer to break granite for a road cut. Despite the rock’s hardness (~30,000 psi), they averaged 60 tons/hour by pre-drilling stress relief holes and using a skilled operator. They noted that hammer alignment and consistent tool pressure were critical to maintaining productivity.
Additional Parameters and Suggestions
- Hammer operating pressure: ~2,500–3,000 psi
- Flow rate requirement: ~50–80 GPM
- Blow frequency: ~300–600 BPM (blows per minute)
- Tool type: Moil point for general rock, chisel for layered formations
- Excavator weight class: 45–55 tons for optimal hammer control
1. Match Hammer to Excavator
- Ensure excavator hydraulic flow and pressure match hammer specs
- Use a hammer with impact energy appropriate for rock hardness
- Drill holes along fracture lines to reduce resistance
- Improves control and reduces tool wear
- Maintain perpendicular tool alignment
- Avoid dry firing (hammering without resistance)
- Use consistent pressure and avoid bouncing
- Inspect bushings and tool wear daily
- Check hydraulic oil temperature and cleanliness
- Replace worn tips to maintain impact efficiency
- Grease tool bushings every 2–4 hours of operation
- Replace seals and diaphragms every 500–1,000 hours
- Flush hydraulic lines before installing a new hammer
- Train operators on hammer-specific techniques and safety
While a CAT 345 with a 10,000 lb hammer is capable of breaking hundreds of tons of rock per day, actual productivity depends on more than machine specs. Rock type, operator skill, tool condition, and site layout all play a role. By approaching rock breaking as a system—balancing equipment, technique, and maintenance—contractors can maximize output and minimize downtime. In the end, the hammer is only as effective as the hands and habits behind it.
