Created on:2022-02-15 13:27

Fault analysis and measures of hydraulic motor of DCY900 beam carrier

Fault analysis and measures of hydraulic motor of DCY900 beam carrier

1. Introduction

DCY900 tire type beam carrier, as shown in Figure m, is a large equipment used to complete the transportation of box girder for high-speed railway from the beam yard to the construction site. Due to the limitation of road conditions, the walking system of beam carrier adopts high-power density closed hydraulic system, 32 groups of suspension are connected through the main beam, of which 12 drive wheel groups adopt closed drive circuit. The machine has large driving force, stepless speed regulation and wide speed regulation range. The operator can realize the forward, backward and fast and slow functions of the vehicle through the control handle.


2. Fault phenomenon

At the construction site, the operators found that the speed of the beam carrier was unstable, the speed could not reach the design parameters, and the system pressure was abnormal. The technician immediately disassembled and analyzed the failed driving motor of the 900t beam carrier, and found that the rear end cover of the motor was hit with obvious marks, as shown in Figure n, the plunger came out of the cylinder block, as shown in Figure o, and the oil distribution plate was seriously worn, as shown in Figure P.


3. Cause analysis

Through analysis, the damage should be caused by overspeed. There are two conditions for overspeed of hydraulic motor:

(1) The output speed of the hydraulic motor is too high. Because the output speed of the hydraulic motor is too high, the oil distribution valve block is lifted, and the subsequent rapid return collides with the rear end cover, resulting in marks.

(2) Changes in vehicle grounding conditions cause excessive flow into individual hydraulic motors. When the vehicle grounding condition is poor or the vehicle goes downhill, if a wheel loses traction, the inlet pressure of its driving hydraulic motor is low. For the system with multiple pumps and multiple hydraulic motors, the flow from the driving pump will preferentially flow into the hydraulic motor with low pressure. At this time, the large flow of oil will overspeed the hydraulic motor.

When the hydraulic motor is overspeed, the plunger may fall out of the cylinder block and be broken due to failure to synchronize.

4. Improvement measures

(1) Scientific option assembly and careful cleaning of the circuit.

When laying pipes for equipment, try to select pipe connection and avoid using hydraulic manifold block. Because the working pressure of closed circuit is generally high, the hydraulic manifold block must use cast and forged steel parts, but it is difficult to completely remove residual iron filings.

When assembling the closed circuit hydraulic system, all hydraulic components and pipe fittings must be strictly cleaned. In particular, the hydraulic hose produced according to the standard process must be selected. Because the quartz sand particles falling off at high temperature during hose cutting will adhere to the inner wall of the hose, which is also difficult to clean. There is no oil filter on the main circuit of the closed hydraulic system. Once iron filings or quartz sand enter, it will circulate with the oil in the main circuit and constantly wear the oil distribution plate, resulting in an increase in the leakage of the main circuit. When the leakage exceeds the oil make-up flow, the main pump will suffer cavitation due to insufficient oil absorption, resulting in the scrapping of the oil distribution plate of the pump.

After the installation of the system, open flushing shall be carried out for the main circuit, that is, disconnect the main circuit, flush the main circuit with other high-pressure and large flow pumps, and then add clean hydraulic oil to the oil tank for vehicle commissioning.

(2) In case of any fault, the following measures shall be taken immediately.

1) Clean the whole closed system pipeline and replace the oil to ensure the cleanness of the circuit.

2) Modify the procedure to reduce the vehicle speed and the possibility of overspeed when driving on the road with poor downhill and grounding conditions.

3) Reduce the no-load running speed of the whole vehicle. If conditions permit, the hydraulic configuration of the system can be improved, such as using solenoid valve or bypass valve circuit to realize hydraulic motor protection; Or on the premise of meeting the vehicle performance, increase the minimum displacement of the hydraulic motor and limit the adjustment current of the hydraulic motor from the program.

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