Wet shotcrete sprayer are key equipment used for shotcrete support in projects such as tunnels, mines, and slopes. Their core function is to achieve rapid, efficient, and high-quality concrete adhesion and formation through the "wet shotcrete" process. The following is a detailed explanation of the working principle of a wet shotcrete sprayer, integrating the core workflow and key technical aspects with industry application practice:
I. Core Subsystem Working Principles
1. Concrete Storage and Pumping System: This system includes a hopper (for storing ready-mixed wet concrete) and a pumping device (such as a hydraulic piston pump or screw pump), responsible for pushing wet concrete under high pressure into the shotcrete pipeline.
2. Compressed Air System: This system uses an air compressor to provide high-pressure airflow to accelerate the concrete at the nozzle, forming a high-speed spray stream.
3. Accelerator Metering System: This system uses a metering pump to precisely control the amount of accelerator (a chemical that accelerates concrete setting) added, mixing it with the concrete near the nozzle.
4. Control System: This system integrates hydraulic and electrical control units to enable coordinated adjustment of parameters such as boom movement, pumping speed, air volume, and accelerator dosage.
II. Overall Workflow
The wet shotcrete sprayer utilizes a mechanized system to achieve a closed-loop operation for concrete preparation, delivery, mixing, and spraying. The specific process is as follows:
1. Concrete Preparation and Transportation
① The mixing station mixes cement, aggregate, water, and additives according to the specified ratio to form ready-mixed concrete;
② Tanker trucks transport the concrete to the construction site and unload it into the wet shotcrete sprayer's hopper.
2. Pumping and Accelerator Addition
① The concrete in the hopper is pushed into the delivery pipeline by a hydraulic pumping system;
② The intelligent proportioning system simultaneously injects liquid accelerator according to a preset ratio (with an error of ≤1%), with a hose pump dynamically matching the flow rate.
3. Air-Material Mixing and Spraying
① The concrete and accelerator are initially mixed at the spray nozzle;
② A high-pressure air compressor (typically 0.7-1.2 MPa) injects compressed air into the mixing chamber, atomizing and accelerating the material, forming a high-speed jet that is sprayed onto the sprayed surface.
4. Setting into Layers
The accelerator triggers rapid hydration of cement, resulting in initial setting of the concrete in 10-30 seconds, forming a dense support layer.
III. Typical Faults and Solutions
1. Pipeline Blockage. Cause: Aggregate oversize or uncleaned after shutdown. Solution: Enable reverse pumping and high-pressure water flushing.
2. Uneven Spraying. Cause: Insufficient air pressure or improper accelerator ratio. Solution: Calibrate the air compressor pressure valve and check the proportioning system.