When the vertical height of pipe laying of small mixer is high or limited by the site, it is difficult to balance the back pressure only by setting horizontal pipe, then it is better to set a cannula (also known as plug valve pipe) between the conical pipe and the straight pipe of the conveying pipe, and close the pipe when the pumping is stopped to prevent concrete backflow. When the vertical height is low, a certain length of horizontal pipe is set between the lower end of the vertical pipe and the small mixer, and the friction resistance between the concrete in the horizontal pipe and the wall of the conveying pipe is used to balance the back pressure.
Generally, the length ratio of horizontal pipe to vertical pipe is 1:3, and should not be less than 15m. When the vertical height is very high, the buffer elbow can be added in the middle of the vertical pipe layer, and the friction resistance between the concrete in the elbow and the wall of the conveying pipe can be used to balance the back pressure to prevent the concrete backflow.
Special attention should be paid to the regular inspection of the pipe wall thickness of the small concrete pump truck. When the wall thickness is worn out, it should be replaced immediately, and the delivery pipe at the position with higher pressure should be replaced together. When the vertical upward pumping height exceeds 30m, the new, wear-free or thick pipe wall delivery pipe should be arranged at the end close to the pump, because the closer to the pump, the greater the pressure in the pipeline. The material of valve core and valve body of small concrete pump truck are different, and the coefficient of thermal expansion is also different. The phenomenon of valve core sticking caused by thermal expansion between valve core and valve body causes small concrete pump truck not to work normally.
When the temperature of the working liquid rises, the viscosity of the working liquid decreases, and the leakage of the small concrete pump truck increases, and the actual flow rate of the pump will decrease; After the hydraulic system of the small concrete pump truck is heated, the viscosity of the working fluid will decrease, and the lubrication performance will also be reduced, which will speed up the wear of the hydraulic components and greatly shorten the service life of the components of the small concrete pump truck.
When the small mixer is heated and the temperature rises, the sealing parts of the hydraulic system and its components are very easy to deteriorate, which will lead to poor elasticity and low sealing. In serious cases, it will lead to seal failure and increase the risk of leakage; In order to ensure the safe and normal operation of small mixer, the phenomenon of heating of hydraulic system should be avoided in the process of use, because its harm is relatively large.