During the spraying operation, it's important to start the air supply before starting the pump and to stop the pump before turning off the air supply. This is done to prevent cement slurry from entering the air circuit. After spraying the concrete, the air passage should be opened after cleaning, and then the nozzle should be removed.

When moving the nozzle during wet spraying with the wet spray vehicle, the nozzle should be moved according to the specific site conditions. The horizontal bar, vertical bar, and circular motion should be used alternately and slowly to ensure that the concrete layer reaches a certain thickness before moving away. Then, gradually expand the spraying area. The spraying sequence is generally from bottom to top, and from wall to arch. If the surface is uneven, the nozzle should first be recessed to fill in the low areas, then move in a spiral or S-shaped pattern slowly and evenly. Each spray cycle should press down on the first half to reduce rebound. The length of each spray should be controlled at 3-4 meters.

Rebound Adjustment for Wet Spray Concrete Vehicle

Rebound refers to the mixture that falls from the sprayed surface due to collision with the rock surface, reinforcement, and aggregate particles. The amount of rebound varies depending on factors such as the spraying location, air pressure, cement content, water-cement ratio, aggregate particle size, and steel reinforcement. Generally, the rebound is larger immediately after spraying, and it decreases once the plastic layer forms. Therefore, the thickness of the first spray layer should not be less than 4 cm. Additionally, rebound materials contain impurities. The angle and distance of the wet spray machine are also important during spraying. In general, the nozzle should be perpendicular to the rock surface, and for sidewall spraying, the nozzle should be tilted downward by about 10 degrees so that the concrete can be sprayed onto the thick concrete top. The top should be sprayed in the direction of the diameter. If the surface being sprayed contains mesh and rebar, the nozzle can be slightly tilted, but should not be less than 70 degrees. The angle should not be too small, as this would cause the concrete material to roll on the spraying surface, resulting in a wavy spraying surface and increasing rebound.

How to Analyze the Wear of Wet Spray Vehicle Concrete Pistons

The overall wear, local wear, erosive wear, scoring, and post-maintenance treatment of the concrete piston.

Local Wear

Main Features of Overall Wear The radial wear on the lips of the concrete piston in the pump components is generally consistent, with the wear marks being relatively even.

Causes of Overall Wear Improper maintenance, poor lubrication, excessive load, or quality issues with the concrete piston (such as oversized dimensions or poor wear resistance of materials).

Handling of Overall Wear Faults

By identifying the wear marks, confirm the overall wear of the concrete piston in the pump components.

Check the cleaning chamber and cooling water to ensure the cleaning chamber is clean.

Remove the dust seal, improve the lubrication and cooling of the concrete piston, add an appropriate amount of hydraulic oil to the cleaning chamber, replace the guiding ring with a new one, and improve lubrication.

Check the dimensions of the concrete piston. Typically, the lips of the concrete piston should be 4-5 mm larger than the diameter of the conveying cylinder.

Replace the concrete piston with one made of different materials if necessary.