Kalmar has launched a quick repair failure case for three consecutive years to help customers solve various equipment failures and reduce equipment downtime. Kalmar will continue to provide quick maintenance fault case sharing on various social platforms this year, and will also release some seminars. Technical text, help customers and maintenance personnel to solve incurable diseases, popularize the theory of locomotive technology, and further help customers improve productivity.
The fifth of the 2018 we will share is the failure to repair the frontal boom with no movement at all.
Author: Kalmar South China Region Product Technical Support Xie Hansheng
Fault description
A Kalmar DRT450 front hoist is normally retracted on the boom. When the driver turns the device back on, the boom will be completely inoperative, and the spreader will operate normally. The device does not display any fault codes.
Failure analysis
The front boom lifts up, down, extends, and retracts completely without action. Field maintenance personnel speculate that the probability of equipment or hydraulic system failing at the same time is small, and there is no fault code in this example, so it is speculated that the fault belongs to the electrical system. The possibility is also very small. After the maintenance personnel according to the normal working conditions of the locomotive, the site is checked step by step, testing and confirming whether there is abnormal operation in the public control part, such as whether the emergency stop switch in the cab is accidentally pressed by the driver? Is the electrical signal input from the handle to the computer normal? In addition, the presence or absence of the driver on the cab seat will also cause the locomotive to be inoperative. After the on-site inspection, the above components are in a normal state.
Then, the maintenance personnel began to view the data on the display terminal of the device. After entering the device diagnosis menu, the driving current of each proportional solenoid valve is compared. The value is normal. This indicates that the solenoid valve is lifted/lowered or extended/retracted. The working condition is also normal, the big arm action solenoid valve on the main valve is as follows:
(Note: The installation position of the proportional solenoid valve on the hydraulic main valve of another model of Kalmar is different from the above picture. Please check the function according to the actual configuration of the equipment)
Troubleshooting
The electrical input signal and output control of the equipment boom are lifted, lowered, extended, retracted, and the fault code is not issued. The field maintenance personnel preliminarily judge that the fault is not related to the electrical system, or is a hydraulic system problem, such as hydraulic pressure. The signal common oil circuit is abnormal, the main valve servo oil circuit is abnormal, etc. Therefore, the maintenance personnel began to inspect the hydraulic system.
According to the analysis of the hydraulic principle diagram, the variable piston pump needs the main valve spool to operate, and the load pressure is generated after the load signal LS is activated. The main valve spool action requires the servo oil pressure to push the main valve spool, so the load signal Whether the LS and servo pressure can operate normally is the condition for the normal operation of the boom.
Then the maintenance personnel carry out the hydraulic pressure test. After starting the equipment, the 60 bar range pressure gauge is used to measure whether the hydraulic gauge and the pressure measuring pipeline are normal. Firstly, the servo pressure of the hydraulic system is measured. The measurement result shows that the servo pressure is 0 bar, and the hydraulic pressure of the normal locomotive. The system servo pressure should be 35bar ± 5bar. The test points are as shown below:
According to the abnormal value of the servo pressure test, the maintenance personnel began to find the cause of the servo pressure being zero. After the engine is started, the servo pressure is directly from the variable pump outlet on the right side of the locomotive through the check valve to the P port of the servo valve group. Pressed and sent to the main valve from the lower H interface. The servo pressure measured by the H port is 0 bar, indicating that the cause of the fault may be damage to the hydraulic variable pump, the oil circuit is blocked, and the servo pressure reducing valve is stuck in the closed state. The valve card can not be opened, etc.. So further troubleshooting:
1. Measure the right side of the locomotive No. 3, No. 4 variable pump backup pressure, the measured value is 29bar and 31bar, normal;
2. Check the P port inlet pipe of the servo valve group, there is oil phenomenon, not blocked, normal;
3. Remove the servo pressure measuring connector, and then remove the internal servo check valve. It is found that the one-way valve is stuck, and the servo check valve is further disassembled. It is found that the internal O-ring is damaged and the spool is stuck. The servo oil cannot pass, the servo pressure is 0bar, which causes the two main spools on the hydraulic main valve to be inoperable, and the boom is completely inoperative. The following figure shows the damaged check valve O-ring:
Solution: Replace the damaged O-ring of the servo check valve, the equipment is running normally, and the boom can move normally.
Summary
When the locomotive has a hoisting action failure, first check whether the prerequisites for the normal operation of these actions are met, especially when no fault code appears. If the seat switch is disconnected, the locomotive default cab seat is unmanned. The control system cuts off the operation of the air handle and the shifting handle, and the device will not operate. This is caused by the internal protection system of the locomotive control system. The direction of the maintenance inspection is not the same as the failure of the equipment components.
If you encounter functional failures in conjunction with electrical and hydraulic systems, resolve as much as possible based on the operating principles of the electrical and hydraulic systems. Then analyze the symptoms and troubleshoot the possible causes from easy to difficult. Maintenance personnel must use the equipment in particular. With its own diagnostic menu, the menu can monitor each input and output signal to improve maintenance efficiency;
When selecting the hydraulic gauge to measure the pressure of the hydraulic system, it is necessary to select the pressure gauge of the appropriate range according to the standard pressure value of the measuring point, so as to avoid the error of the measurement result being too large. Selecting the unsuitable measuring tool may even mislead the maintenance inspection direction. Measuring variable pump When preparing for pressure, if the hydraulic gauge of 400bar range is used, under normal circumstances, only the small movement of the pointer of the hydraulic gauge can be seen, and it is difficult to measure the accurate pressure value.
The quick maintenance fault case and seminar technical texts are compiled and compiled by the Kalmar Asia Training Center (KATC). Please indicate the source for forwarding.
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