During the improvement of the QLB-30 asphalt concrete mixer, the problems of fracture and weld opening have not occurred again.

In 1993, the Highway Management General Section of Shangluo Prefecture, Shaanxi Province, purchased the QLB-30 asphalt mixer produced by Wuxi Xin 'an Transportation Engineering Machinery Factory. During its use, some faults occurred. After several years of repeated renovations, the usage effect has been good. Now, we introduce our improvement methods as follows.

1 Feeding device

When the mixed material containing oversized stones falls from the batching hopper to the feeding outlet, due to the small gap and poor discharge, blockage and jamming occur. Within less than 20 shifts, the sharp and hard stone blades repeatedly and severely cut the running rubber conveyor belt. In addition, when the material stones are piled up in the open air, due to rain or the high moisture content and sand content of the temporarily selected granular materials from the river, they stick together. Also, due to the influence of the self-locking Angle of the feeding hopper, the material stones arch and accumulate, resulting in poor material discharge. The improvement and repair methods for it are as follows:

(1) Without changing the structure of the raw material hopper, like the Italian company Marini, install a vibrator on the outside of the hopper to eliminate arching and accumulation phenomena and ensure uniform feeding.

(2) Install a 10×10cm grid in the feeding hopper to prevent stones larger than 10cm from entering the discharge port, which may jam the discharge port or scratch the belt.

2 Drying cylinder

As the drying drum operates at high temperatures and is installed outdoors, it is constantly exposed to rain, snow, wind, frost and sunlight, making it prone to rust and corrosion. After the operation stops, cool it down slowly. After the fault is eliminated or when it starts working the next day, heat it up again. This not only wastes thermal energy but also causes damage to the cylinder. The suggestions for its improvement are as follows:

(1) The material of the drying cylinder must be heat-resistant steel to reduce oxidation corrosion.

(2) The latest design of the British Parker Company can be adopted, with an insulation layer designed on the circumference of the drying cylinder. This can make full use of thermal energy and improve thermal efficiency. Reduce oxidation, extend service life and lower costs.

3. Bottom of the hot material elevator

The hot material elevator system used in our section elongates the lifting chain due to heat conduction, heat radiation and gravity. Occasionally, it changes position, detaches from the sprocket and stops running, forcing the hopper to stop working and causing the hot material to accumulate in the pit. In addition, due to the inertia of the drying cylinder, the discharge cannot be stopped instantly, which aggravates the accumulation of hot materials and paralyzes the entire production process. At this point, the temperature of the material stones is between 150℃ and 170℃. Due to the high temperature and the narrow pit (the pit foundation is designed as a rectangle with a depth of 1.5m, a cross-section length of 1.6m, and a width of 1.5m. After removing the hoist part, the widest part is only 0.3m, which can only accommodate one person), it is impossible to remove the material stones. The only way is to cool the hot materials and then remove them bit by bit with a shovel. Secondly, there should be no malfunctions. Due to the narrow pit, normal adjustments, lubrication, and the tightening of chains and sprockets cannot be carried out.

We modified the pit without affecting the force on the original foundation: extending 1 meter to the bottom of the front of the hopper and making it in a slope shape. If the above situation occurs, the hot material will be quickly cleared to the open space (i.e., the expanded 1 meter), the fault will be eliminated, and the waste material will then be pulled out from the slope by a handcart. The ground of the renovated area is covered with a cover plate, which does not affect the normal operation of the surface part.

Outlet of the hot material elevator

The bottom of the discharge port of the elevator is welded with 2.5mm thick ordinary steel plates. Due to the effects of heat conduction, gravity, impact and friction, the wear is quite severe. The new machine was worn through after only 18 shifts of use. In a short period of time, the perforated area expanded rapidly, and 60% of the lifted hot material was thrown from the top, forcing the operation to stop. The method of repair requires the complete removal of this part, taking it down from a height of 10 meters, repairing it and then reinstalling it, which is both inconvenient and unsafe. Our improvement method is to insert 8 to 10mm heat-resistant movable thick steel plates or 3 to 5mm chromium-manganese steel plates. Once they are worn through, replace them with steel plates of the same material and specification without the need for overall disassembly, cutting or welding.

5. Screening machine screen

The screen mesh is fixed to the frame with bolts. It needs to be replaced frequently when it wears out or is worn through. If the material of the screen mesh does not match, it will wear out even faster. However, the screen is installed at a high altitude, making it very inconvenient to replace it. We believe that all domestic models can adopt the removable and replaceable screen structure of Marlini Company, which is safe, reliable and convenient.

6 Asphalt cylinder

This machine's mixing cylinder mixes asphalt by self-pressure inflow and forced mixing, so the mixing effect is average. It can be used in production, but it fails to meet the strict theoretical quality requirements, especially with mixing dead corners at both ends. There is still room for improvement in shortening the mixing time, enhancing the mixing quality and increasing productivity. Our suggestions for improvement

(1) The mixing cylinder can adopt dual motors with synchronous drivers to address the drawbacks of synchronous mixing shafts and the large torque and heavy load of the driving shaft after reducing the drive of one shaft.

(2) The structure of the mixing cylinder of Marini Company is adopted. A low-pressure asphalt pump is added outside the asphalt spray cylinder to spray the measured asphalt into the mixing cylinder. If it is atomized and sprayed, the effect will be better, and the mixing time can be shortened and the mixing quality can be improved.

The structural design of the 7 mixing feet

The design of the mixing feet of this machine is similar to that of similar domestic models. Once worn out, they have no value for reuse and can only be discarded. Due to the special material of this part, its high cost and rapid wear, with a utilization rate of less than 60%, we suggest adopting advanced foreign technology to design it as a structure that can be flipped over and moved on the shaft, in order to improve the utilization rate and reduce the cost.