Precautions for the Use of YZT18 Type Towable Vibrating Roller

The towable vibrating roller features a simple structure and strong vibration force. At present, the YZT series of towable vibratory rollers produced domestically are widely used in our country.

Four YZT18 type towed vibratory rollers were used in the construction of the 砼面板 rockfill dam of dahe Power Station and the 砼面板 rockfill dam of gaotang Power station in Guangdong Province. Some notable problems were found during their use.

1. Engine

The engine equipped on the YZT18 vibrating mill is the F6L913-ZG six-cylinder direct injection air-cooled engine produced by the Kitaichi Group, which is a product based on the engine technology of Deutz in Germany. In actual use, the major and medium repair intervals for each engine are only 3 to 6 months. That is, on average, medium or even major overhauls need to be carried out every 3 to 6 months, and in the fastest cases, the piston rings need to be replaced within a week. The main type of damage is that the piston and cylinder liner assemblies wear out too quickly due to engine overheating or dirty intake air, and sometimes it is cylinder pulling. There are two reasons: On the one hand, the air-cooled engine equipped is not suitable for the vibrating roller used in rockfill dam compaction in the first place. This is because the engine guard frame of this machine does not have a dust-proof function (due to the unreasonable design, the guard frame is basically removed before use), and the amount of dust generated during compaction work is large, which increases the working intensity of the air intake filter element and also greatly affects the working efficiency of the air-cooling system. It leads to the engine being prone to damage; On the other hand, when domestic parts were used to replace the cylinder head and intake and exhaust manifolds on this engine, structural changes occurred, making the intake and exhaust channels narrow. As a result, the intake and exhaust volumes failed to meet the requirements during high-speed operation, which not only affected the engine's power but also caused the engine to overheat (this point has been agreed upon with the manufacturer).

To extend the service life of the engine, the following aspects should be noted in actual use:

(1) Try to use air filters with both internal and external dual formats as much as possible. The quality of the filter elements should be good to improve the intake air quality. If a set of oil-immersed filter elements is added, it will also play a certain role.

(2) Regularly check whether the tensioning device of the fan belt is working properly and its wear condition. When problems occur, they must be repaired or replaced in a timely manner.

(3) Regularly check whether the fan bearings are normal.

(4) Try to keep the cooling air channels clean and sealed to increase the flow of cooling air and reduce losses. For areas with significant air leakage, timely correction or repair should be carried out. Regularly clean the cooling air channels with pressurized air or pressurized water when the machine is cold.

(5) After long-term use and comparison, it is recommended to use CD grade engine oil to ensure that the engine is not damaged due to oil quality issues.

(6) Try to avoid long-term high-speed operation. Generally, medium speed should be the main choice.

(7) For engines that need to run at high speed for a long time during operation, it is recommended to replace the cylinder head, intake and exhaust manifolds, and turbocharger with imported ones. Although this will cost about 20,000 yuan more than domestic parts, which is equivalent to the cost of replacing three domestic parts of the engine, considering the losses caused by machine maintenance, it is still cost-effective to replace the imported parts.

2 Vibration system

The feature of this series of vibrating rollers is that they have a large vibration force. The vibration system is designed with the following features: The excitation force is generated by three eccentric blocks installed on three shafts. The shafts are driven by involute gears, and each shaft is supported by two 3620 type bearings. The bearings are lubricated and cooled by closed lubricating oil splash lubrication. To mitigate the impact of the excitation force (400 kN) on the engine and fuselage, this machine adopts a tire vibration reduction system, that is, a 7.5-20 specification tire is installed at each end of the vibration cylinder, which serves to reduce vibration and support the frame. It adopts a two-stage belt drive method; To eliminate the heat generated by the vibration cylinder during operation, the structure of the vibration cylinder adopts a double-layer hollow type, which is connected by welding, and cooling water or oil is placed in the cylinder wall.

Although these designs have certain advantages, they have also brought about the following problems in use that affect the efficiency of machine operation:

(1) The closed lubrication system of the eccentric shaft support bearing is sealed by two oil seals. Due to the fact that the quality of domestic oil seals is not yet fully up to standard, the phenomenon of lubricating oil leakage due to the damage of the lubricating oil seals often occurs. And this kind of fault is relatively concealed and not easy to be detected, so it may cause the bearing to work for a long time under poor lubrication and cooling conditions, leading to damage. The types of damage include: bearing damage, worn bearing housing, broken transmission gears and eccentric shaft breakage, etc. Among them, the wear of the bearing housing is the most difficult to repair, mainly because it is hard to ensure the coaxiality of the three shafts. Two vibrating rollers with this kind of malfunction cost us a lot of time and money to repair, but the usage effect after repair was very poor and they were basically unusable.

(2) Although tire vibration damping has the advantages of good vibration damping effect and simple structure, it also has many shortcomings and problems. Firstly, the air pressure of the two tires must be maintained between 0.50 and 0.55 MPa; otherwise, the vibration damping effect will be poor, and long-term insufficient air pressure will lead to faults such as wear of the tire seats and eccentric shafts. Secondly, the pressure difference between the two tires must not exceed 0.02 MPa; otherwise, due to the unevenness on both sides, the secondary drive belt will frequently flip or fall off. Therefore, it is necessary to check and replenish the tire pressure in a timely manner. Due to design issues, when dragging and rolling, the tires will rotate relative to the frame. Sometimes, the air nozzles will turn to a position that cannot be inspected or inflated. To inflate, the frame must be disassembled, thus increasing the trouble and difficulty. In the early stage of using this vibrating roller, we experienced many such incidents. Later, we made changes to the frame structure covering the tires, which changed this passive situation.

(3) The welded connection parts of the vibrating cylinder are prone to wear through the weld beads due to frequent friction with stones, thus causing water leakage. The cooling water in the cylinder not only serves the cooling function but also enhances the strength of the cylinder body. Once leakage occurs, the strength of the vibrating cylinder decreases. Under strong vibration force, it is prone to damage. Re-welding is time-consuming and laborious, which affects its use.

To maximize the integrity and utilization rate of the vibrating mill, the following aspects of work should be done well in daily operations:

(1) The flatness of the rockfill dam surface should be as good as possible. The stones used should not be too large or seriously exceed the standard to reduce the damage caused by the unevenness of the vibration roller.

(2) Strictly adhere to checking the tire pressure at each shift. When insufficient or asymmetrical pressure is found, it should be replenished in a timely manner.

(3) Regularly check whether the lubricating oil of the eccentric shaft bearing is leaking. If leakage is found, it should be dealt with in time to avoid greater damage.

(4) Regularly change the lubricating oil to ensure its quality.

(5) The four limit wheels at both ends of the vibration cylinder must be in normal operation. If they are damaged, they should be repaired or replaced in time to avoid adverse effects caused by the left and right swinging of the vibration cylinder.

(6) After about 2,000 hours of use, the performance of the eccentric shaft bearing should be checked to see if it is good. Bearings that are not working well should be replaced in time to avoid more serious damage.