Below is a clear, engineering-oriented explanation based on common site practice.
1. Basic Conversion Principle
A boom pump truck already provides:
Long-reach articulated boom
Hydraulic system
Concrete pumping pipeline
The conversion focuses on replacing the concrete discharge system with a wet shotcrete spraying system, while adding air and accelerator functions.
2. Key Modifications Required
① Spraying Nozzle Assembly
Replace the original concrete outlet with a wet spraying nozzle
Nozzle includes:
Compressed air inlet
Accelerator inlet
Adjustable spray angle
Anti-rebound and anti-blocking design recommended
② Accelerator Dosing System
Install an alkali-free liquid accelerator pump
Flow rate is linked to concrete output (typically 3–8%)
Controlled manually or electronically
Accelerator is injected at the nozzle, not in the pipeline
③ Air Compressor System
Add a high-pressure air compressor
Capacity: ≥7–10 m³/min
Pressure: 0.7–0.8 MPa
Power options:
Chassis PTO driven (preferred)
Independent diesel compressor
Air line routed along the boom to the nozzle
④ Pipeline & Wear Parts
Replace standard pump pipe end with:
Shotcrete-grade wear-resistant pipes
Flexible rubber hose at boom tip
Install quick-release couplings for cleaning
⑤ Control & Safety Upgrades
Emergency stop near nozzle
Pressure relief valve
Boom motion lock during spraying
Remote control optional for tunnel use
3. Typical Technical Parameters (After Conversion)
| Item | Typical Value |
|---|---|
| Spraying capacity | 15–30 m³/h |
| Max spraying distance | 20–28 m (boom dependent) |
| Accelerator dosage | 3–8% |
| Rebound rate | ≤15% |
| Concrete slump | 120–160 mm |
4. Application Scenarios
✅ Tunnel initial support
✅ Hydropower tunnel lining repair
✅ High-slope stabilization
✅ Underground cavern reinforcement
✅ Emergency support works
5. Advantages of This Conversion
Low investment cost compared with dedicated shotcrete robots
Long boom reach for high or deep sections
Strong pumping ability for large aggregate concrete
Quick deployment on existing equipment
6. Limitations to Note
⚠ Less precise spraying than robotic shotcrete machines
⚠ Higher rebound if nozzle control is poor
⚠ Requires experienced nozzle operator
⚠ Not ideal for small or very narrow tunnels
7. When to Choose This Solution
A boom pump conversion is recommended if:
You already own a concrete pump truck
Project volume is medium-scale
Tunnel section is ≥6 m wide
Budget or delivery time is limited
