1、 Introduction to shield tunneling machine

Shield tunneling machine, abbreviated as shield tunneling machine, is a commonly used equipment in underground mechanical engineering. It is a comprehensive large-scale construction machinery that integrates mechanical, electrical, hydraulic, measurement and control technologies. It has the advantages of high automation, labor-saving, low noise, fast construction speed, one-time tunneling, and is not affected by climate. It can be used for excavation, soil dumping, lining and other work, and is widely used in urban rail transit, railway, highway, municipal, hydropower and other tunnel projects.

2、 The parts of the shield machine where grease is used

IIICommon lubrication faults of shield tunneling machines

The cross policy for maintenance and upkeep of shield tunneling machines is to clean, lubricate, tighten, adjust, and prevent corrosion. It can be seen that faults caused by poor lubrication are one of the more common faults of shield tunneling machines. Lubrication mainly refers to the lubrication of sliding tracks and dynamic seals of moving parts (main bearing seals, screw conveyor seals, mortar mixing shaft seals, rotary joint seals, handover seals, shield tail seals); Lubrication of bearings (oil lubricated bearings, high-temperature grease lubricated bearings, grease lubricated bearings); Lubrication of transmission components (gearbox, chain); Adjustment: main bearing sealing slideway, screw engine door seal, belt scraper, tugboat, propulsion cylinder support, foam parameters, grease parameters, etc. Let's take a case study to understand some of the faults that occur in shield tunneling machines due to poor lubrication.

Case 1: Bearing wear

The picture shows the disassembly and maintenance of the main drive bearing of the shield machine. It can be seen from the picture that the bearing is severely worn. The shield tunneling machine did not monitor the grease during daily use, and it was unknown whether the equipment had abnormal wear and tear. It was not until the equipment was shut down due to serious malfunctions that uneven grease injection in the main drive was discovered during maintenance, resulting in excessive seal wear and causing equipment failure.

Case 2: Corrosion of oil cylinder

This is a photo of the dismantling and inspection of the propulsion cylinder of the shield machine. It can be seen from the photo that the chrome plating layer on the surface of the propulsion cylinder rod has peeled off, and the cylinder rod is corroded. The reason for this phenomenon is that during the excavation process, there was oil leakage and pressure relief in the propulsion oil cylinder. Due to the construction of the shield machine in high water content strata, water pollution occurred, and groundwater penetrated to the tail of the shield. Due to the failure to detect it in time, the sewage was discharged, and the oil cylinder was corroded under the immersion of sewage for a long time, causing the chrome plating layer on its surface to detach, which later affected the normal operation of the propulsion system.

Case 3: Oil cylinder leakage

From this picture, it can be seen that the equipment has experienced oil leakage from the oil cylinder. Due to hydraulic oil leakage, the extension of the oil cylinder may be abnormal, causing the cylinder to fail to reach the pipe segment, which in turn affects the normal propulsion of the equipment.

Case 4: Leakage of mortar at the shaft end of the mortar tank

This picture shows the leakage of mortar at the shaft end of the mortar tank. After dismantling and inspection, it was determined that the cause was insufficient lubricating grease in the bearing and sealing ring parts, resulting in wear of the bearing and sealing ring. Fine sand in the mortar can easily enter the bearing, and as the mortar is stirred and rotated, it can cause bearing wear and seal failure.

Case 5: Tail brush plate structure

This picture shows the tail brush being laminated, causing the tail brush to be inelastic and unable to contact the pipe segment. The reason for this phenomenon is that there is a serious water and slurry leakage problem at the tail of the shield, and the consumption of grease at the tail of the shield is greater than the normal consumption value. In the process of shield tunneling, the friction between the shield tail brush and the pipe segment consumes grease proportional to the tunneling speed. If the speed is too fast, the grease injected into the shield tail cannot meet its consumption per unit time, and the pressure inside the shield tail cannot seal the shield tail in time, which will inevitably weaken the sealing effect and cause leakage of slurry at the shield tail.

Case 6: The sealing ring of the reducer is broken

This picture shows the main drive reducer, which has undergone severe corrosion, causing the sealing ring to break. After the sealing ring broke, water leakage occurred, causing the equipment to malfunction. The reason for corrosion is that when the shield machine is injected with circulating water, the quality of the circulating water is poor, and the impurities and hardness content have seriously exceeded the standard. These water have a great impact on the pipelines and components, causing severe corrosion of the cooling water channel of the reducer and the fracture of the sealing ring.